Garth Batchelor

 In January 2012 I was on a raptor and wildlife watching trip in South Africa with Bill Clark, Sergio  Seipke and raptor enthusiasts from The Netherlands, United States and Germany. We spend more than 3 weeks visiting many great places and meeting many great people like André Botha, Peter Steyn, Rob Martin, Jessie Walton, Malcom Wilson and Ann Koeslag. We had many highlights incl. 5 species of cats, Martial Eagles, Taita Falcons, Black Harriers and much more. My personal highlight was the African Crowned Eagle. Bill managed to organize for us to meet Garth Batchelor, one of South Africa’s leading experts on the Crowned Eagle. When we met Garth on our last day in Kruger Nationalpark we already had two short and not very good glimpses of Crowned Eagles but we were hoping to get a much better view. The next day Garth took us too a beautiful place and showed us not only an almost fully fledged juvenile (see picture below) but the adult pair also appeared flying above us and we had a fantastic morning there. Garth is not only a really nice guy but he answered all my questions – and I asked a lot – with lots of fantastic information about this beautiful and powerful eagle. I am very happy that Garth agreed to do this interview and share his knowledge about the ecology and conservation of the Crowned Eagle in South Africa. The situation in  South Africa gives reason for hope and with dedicated people like Garth working for the conservation of African Crowned Eagles I am optimistic for the future of Africa’s most spectacular and fascinating bird of prey.

Markus Jais, Germany

1) What is the current status of the African Crowned Eagle in South Africa?

The African Crowned Eagle is currently classified as near threatened in South Africa. This means that its population should be monitored.

2) How has the population developed during the last decades?

It is my perception that the population of this eagle have probably remained fairly constant over the past decade or more. This is due to the fact that they live in remote usually fairly densely forested, mountainous habitats. These areas are often largely inaccessible. They are also secretive birds being difficult to see during most of the year. The often sit quietly on favorite perches often in deep shade for hours waiting for prey to pass by.

Female African Crowned Eagle, © Garth Batchelor

3) How does habitat destruction affect the African Crowned Eagles?

Fortunately the patches of temperate forest along the mountain ranges in South Africa are all protected. These forest patches are the favoured habitat for these large eagles and provide habitat for small antelope such as Blue and Grey Duiker as well as Bushbuck and Vervet and Samango Monkeys. In the Eastern Cape they live in thick succulent vegetation which is very thorny with many euphorbias.

4) Does illegal and maybe legal bird trade threaten the African Crowned Eagle in South Africa?

There is little recorded trade in African Crowned Eagles. Only a limited number of these eagles are kept by falconers under license. The collection of wild birds is strictly controlled by the conservation agencies.

African Crowned Eagle with chick. Note the impala leg! Quite a large meal for such a small bird. This impala was probably a year old and would have weighed about 20Kg or more. © Garth Batchelor

5) Are many birds shot or poisoned?

This is difficult to answer. It is probable that immature birds are shot or trapped if they hunt in urban areas or rural villages. An incident was reported to a forester by a labourer of a big bird catching and killing his small pigs. Fortunately the culprit eagle was not killed even though the nest with a chick in was less than 200 meters from the homestead. There are other reports of “urban“ eagles taking pet dogs and cats. They are definitely opportunists and will take live prey what is available that they can overpower.

6) What other threats affect the African Crowned Eagle?

Being a predator they will always come in conflict with small stock farmers. Goats are easy prey and in the Eastern cape where goats and sheep are farmed extensively farmers will shoot these eagles. In the area around Nelspruit there are a number of conservancies where antelope are farmed for hunting. The African Crowned Eagles will take the young of many antelope species including Bushbuck , Grey Rhebok and Impala. This can be difficult for the farmer to tolerate but generally they are sympathetic to the eagles.

7) What is known about the diet and food requirements of the African Crowned Eagle in South Africa?

As mentioned African Crowned Eagles are opportunists. They will take prey that is available in their territory that they can overpower. In a study on the prey items around Nelspruit in antelope formed over 70% of the diet with Vervet Monkeys also featuring highly.Other prey items included Genet Cats, mongoose, and a small porcupine. Porcupines are normally nocturnal so this is a mystery. In other areas of South Africa Rock and Tree Hyrax are selected. Birds such as Guinea Fowl and even Hadedah Ibis have been recorded as prey. The bones of prey once they have been pecked clean of muscle and sinews are dropped over the edge of the nests and these are recycled by Bush Pig and also by Porcupines.

Juvenile African Crowned Eagle, © Markus Jais

8 ) What habitat do they need? Can they live in habitat altered by humans?

African Crowned Eagles require forest with large trees. The nest tree is usually one of the tallest in the forest and can be up to 30m high. They also seem to select areas which are mountainous. This could be because they perform intense aerial displays before mating and use updrafts often associated with cliff edges to rise up quickly from where they can perform their displays. They appear to have adapted well to areas where extensive plantation so f exotic trees have been planted for timber. These trees may provide nest sites in the larger trees that have become wild in some of the drainage lines reached 30 or more metres i9n height. Pine plantations also support healthy populations of Grey Duiker which are a preferred prey item. Sub Tropical fruits are grown around Nelspruit which can attract Vervet Monkeys. As African Crowned Eagles also readily hunt Vervet Monkeys they are actually welcomed by fruit growers.

9) How large are the typical home ranges of an established pair?

Around the Nelspruit out of a sample of 40 nests, we have calculated the average territory to be about 30 square kilometers. This is small for an eagle of their size compared to a Martial eagle which has a territory size of about 250 square kilometers.

Watching Crowned Eagles in South Africa. Garth Batchelor (center), Exon Twala (right) and the interviewer Markus Jais (left), © Markus Jais

10) What is known about the dispersal and movement of juvenile and immature birds?

This is one of the big questions that we would love to answer. The fate of the juvenile birds after leaving their home territories is not known.

11) How often do African Crowned Eagles breed? How long does it take for them to raise a chick?

African Crowned Eagles have one of the longest breeding cycles of any eagle. In this respect they are similar to the Harpy Eagles of the Amazon. The nest building starts in the middle of winter, in July or early August. Egg laying can be at the end of August but is usually in September and sometimes even October. Incubation is about 51 days while the chick will take up to 110 days to fledge. I have recorded the fledged chick still being in the vicinity of the nest 9 months after fledging and still being tolerated by the adults. The long period required for the chick to become independent is presumably the reason why these eagles breed every second year. Pairs have been recorded to breed annually but we suspect that when this occurs it is because something has happened to the chick.

12) What is the average breeding success? Are there any cases with two chicks successfully fledging?

We have recorded that remote secure territories continually raise a chick every second year whereas nests close to urbanization more frequently attempt to breed annually. Without actually marking the chicks it is not possible to say definitively what is a happening to the fledged chicks but suspect there is a higher mortality of chicks closer to human settlements. We have not recorded two chicks surviving even though two eggs are usually laid .

African Crowned Eagle: Prey remains, © Markus Jais

13) What is known about the relationship with other eagles like Martial Eagles or other raptor species? How are they ecologically separated?

There has been no research on this subject but suspect that African Crowned Eagles are better adapted to a forest habitat. They are like giant Goshawks with round wings and long tail making them very maneuverable in thickets. They spend most of the time sitting unobtrusively waiting for prey. Martial Eagles are master gliders spending most of the day in the air at high altitudes. They are in my view more suited to open savanna where as the Crowned Eagle is a forest specialist. This is born out by the large territories of the Martial Eagle.

14) Do Crowned Eagle benefit from private Game Farms?

They can benefit from game farms unless the owner of the farm considers them a threat to his livelihood. Most game farmers however welcome the eagles on their farms .

15) What gaps in our knowledge of this large eagle do still exists?

The biggest gap in our knowledge is knowing what happens to the immature birds after fledging. Together with this is whether some pairs or populations actually do breed annually as suggested by some researchers.

16) Where should research focus during the next years?

In trying to provide answers for the above two questions. The fitting of satellite transmitters could provide answers to these questions.

The number of nests being monitored should be expanded with ideally working groups starting up throughout their range.

17) What can and must be done to secure the survival of the African Crowned Eagle in South Africa?

Instill a greater awareness and appreciation of these birds amongst landowners who have them nesting or using their properties

18) What is the Crowned Eagle working group and what are it’s tasks and projects?

The Crowned Eagle Working Group (CEWG) consists of a few members of the local Lowveld Bird Club which is a branch of Birdlife South Africa. All landowners with African Crowned Eagle Nests on their properties are automatically members. A core group of members attempt to monitor the breeding success of each nest annually. When possible, prey remains below the nests are recorded and identified. It was realized that after starting to locate nests in the vicinity of Nelspruit that there is strong population of these eagles around the town. We are now monitoring the breeding success of 40 pairs within a radius of 70km from Nelspruit. The CEWG is working closely with all the forestry companies along the Drakensberg escarpment as well as with game farm owners advising them on the conservation of the CE.

The CEWG supported a student from the UK in 2009 to undertake a master degree on the ecology of the Crowned Eagles and would support further research initiatives.

19) How do you see the future of the African Crowned Eagle in South Africa and beyond?

With the growing awareness on these eagles by landowners and the positive support the CEWG has received over the past few years I am confident that the African Crowned Eagles around Nelspruit are in good hands. From communication we are receiving from other Provinces it would appear that this eagle is managing to maintain its populations and is even surviving in developed urban environments.

20) What was your most amazing experience with the African Crowned Eagle?

Standing on the edge of a massive cliff on the Drakensberg Escarpment at Kaapschehoop 30 km west of Nelspruit in early July 2009 I witnessed one of the most thrilling aerial displays that one could wish for. From down in the valley below a pair of African Crowned Eagles soared up in spirals until they were almost out of sight in the clouds. They then started to display calling loudly all the time. They approached closer and closer towards my wife and I till they were only meters away rolling, looping and diving through the sky.

The two following photos were taken by myself on this occasion.

African Crowned Eagle displaying, © Garth Batchelor

African Crowned Eagle displaying, © Garth Batchelor

Sonja Krueger with Bearded Vulture

I have had the privilege of working with Sonja Krüger and observe her
dedication and drive to conserve the Bearded Vulture in southern Africa
since 2004.  Working as an Ecologist with KZN Wildlife and as the
coordinator of the Bearded Vulture Task Force of the EWT’s Birds of Prey
Programme, Sonja has been able to successfully implement and adapt our
approaches to the conservation of the species in our region across its
entire range and involving stakeholders from a range of international,
national as well as provincial institutions and NGO’s while involving
land-owners and other communities in this initiative. Sonja’s dedication is
expressed in so many ways, but conducting monitoring in the
Maloti-Drakensberg in mid-winter, often on foot, and spending hours in a
variety of cramped hides waiting to capture birds for tracking purposes are
two examples thereof. The scope of work and advances made in conservation
action focused on Bearded Vultures in the region are further testament to
Sonja’s hard work in ensuring that these birds will remain the flagship
species associated with the Maloti-Drakensberg and resulted in Sonja being
awarded the Vulture Conservationist of the Year Award in 2007. She is
cuurently completing her PhD focused on this species with the university of
Cape Town.

André Botha, South Africa

1) What is known about the current status of the Bearded Vulture in Africa?

The isolated population in southern Africa has about 100 breeding pairs in the Maluti-Drakensberg mountains with a total population of between 300 and 350 individuals. Ethiopia is still believed to be the stronghold of the species in Africa although no recent estimates exist. Only a few pairs are left in Kenya, Uganda and Tanzania.

2) Has the population changed during the last decades?

Detailed research was done on the species in southern Africa in the 1980s. At the time the population was estimated at 200 breeding pairs. Many nest sites in peripheral areas have been abandoned and the breeding range has reduced in size. It is assumed that this is as a result of increased human disturbance at these sites, either infrastructural developments or increased population density and intensity of farming activities.

Adult Bearded Vulture, © Stephanie Walters

3) What is known about the genetic difference between the birds in southern and eastern Africa and those outside of Africa?

The population south of the Tropic of Cancer (Gypaetus barbatus meridionalis) is thought to be genetically distinct from that north of the Tropic of Cancer in Africa, Europe and Asia (G. barbatus barbatus). Godoy et al. (2004) on the other hand suggest that the global Bearded Vulture population could be treated as a single population since there is no significant difference in life history traits, morphology, habitat or behaviour. However, their assessment was based on only three samples from sub-Saharan Africa. Samples from southern Africa are currently being analysed to increase the sample size to substantiate the finding of Godoy et al. (2004). The results of these findings have implications on the future management of the population

4) What is the preferred habitat of the species?

The birds prefer mountainous terrainand escarpments where they nest in potholes on cliff faces at altitudes above 1800m and on average at 2800m. They forage over lowland areas, over open terrain where they can spot carcasses at a distance.

5) Is there competition with other raptors about food and nesting places?

Since the Bearded Vulture’s diet consists almost exclusively of bone (which is swallowed), there is no competition at feeding stations. They are famous for carrying bones to heights from which they drop them to break them into smaller pieces that can be swallowed with ease. Adults do require meat in the breeding season to feed the chicks. Corvids have been seen harassing Bearded Vultures at established feeding stations where small bone fragments and pieces of meat are placed out for the birds. These morsels appeal to most of the large raptors and the Beardeds tends to steer clear of a lot of scavenging activity.

Bearded Vultures are often found nesting close to Cape Vultures. The habitat preference and choice of nesting sites of Verreaux Eagles is similar to that of the Bearded Vulture and altercations between these two species occur frequently.

Adult Bearded Vulture flying, © Sonja Krueger

6) What is the main food for the Bearded Vulture? Is the Bearded Vulture dependent on Livestock?

Ideally the birds feed on the carcasses of small to medium sized mammals, although bones of larger animals can be broken into smaller pieces. A large part of the species’ range is open grassland where livestock (sheep, goats, cattle) are abundant in summer. In winter, the birds are more reliant on supplementary feeding at feeding stations. In protected areas they feed on wildlife carcasses/afterbirths, particularly when these are plentiful in summer during the lambing/calving season.

7) How important is the presence of large carnivores like lions or leopards as a provider of carrion for the Bearded Vulture?

Large carnivores are scarce throughout the range of the species, therefore these are not important providers of carrion. Bearded Vultures inhabit harsh environments where many animals succumb to the affects of adverse weather and accidental deaths in steep, hostile and inaccessible terrain. Land use change over the past few decades has resulted in large scale transformation of their habitat making supplementary feeding a necessary conservation management action.

8 ) Are Bearded Vultures affected by poisoning?

Poisoning is one of the primary causes of mortality. To date three out of 14 birds fitted with satellite tracking devices have been killed by poison. Bearded Vultures are often accidentally poisoned when feeding on poisoned bait meant for jackal. Since all vulture species are particularly sought after in the traditional medicine trade, the Bearded Vulture is not spared from deliberate poisoning, although they may be more difficult to target. Many herdsman still believe that the birds prey on lambs and deliberately shoot or poison them.

9) In Europe, Bearded Vultures are threatened by lead poisoning (by ingesting lead ammunition). How is the situation in Africa?

Conservation agencies in southern Africa are well aware of the lead threat and are making every effort to inform the public and hunting fraternity of this threat as well as changing the type of ammunition used, the method of culling and disposal of carcasses. Wild caught birds that have been tested for lead levels have not shown unusually high levels of lead. Limited hunting takes places within the range of the species.

Bearded Vulture nest, © Sonja Krueger

10) What other threats for the species do exist?

Collisions with energy structures such as powerlines and wind farms remain the next biggest threat to the species. Additional threats include habitat loss and food shortage as a result of land use change and improved animal husbandry. Human persecution and nest disturbance, are minor threats in Africa but the impacts of mountain climbing on nesting success still needs to be investigated. New threats to the species include their potential vulnerability to climate change and requires further investigation.

11) What is known about breeding success and the annual survival of Bearded Vultures?

The breeding success of the species within their core range is high and similar to that found in the 1980s (about 85%). However breeding success at peripheral sites is much lower with many of these sites having been abandoned over the past few decades.

There is limited recent information on the survival rate of the species. A marking programme has been initiated to provide more information on this and research is being done to determine the number of individuals that survive to the next age class. The average annual adult survival has been estimated at 95% and other age classes have a average survival rate of 11% . Longeivity is estimated at about 20 years in the wild.

12) What gaps in our knowledge about the Bearded Vulture do exist and where should research focus in the next years?

Research should focus on i) which environmental variables account for the abandonment of breeding territories, ii) whether there are age specific differences in the spatial and temporal use of home range that places the birds at risk, iii) whether the population has enough genetic variation and is genetically similar to other populations in sub-Saharan Africa, iv) what the primary factors affecting survival and breeding success of the population are, and v) what the future growth rate of the population is likely to be and vi) what the conservation interventions are that can effectively influence this trend.

13) What needs to be done to secure the future of the Bearded Vulture in Africa?

There is an urgent need to address the threats to the species in particular the threat of poisoning and ever increasing threat of land use changes and associated infrastructural developments (e.g. powerlines). Education and Awareness of the great public on the importance of the species and its role in the environmental is essential. Captive breeding for supplementation of the wild population must be considered but will only be implemented once the threats to the species have been adequately addressed.

14) Are there any conservation projects or research projects for the Bearded Vulture?

A Biodiversity management Plan is in preparation for the species which details the conservation objectives for the species and lists the operational goals required to address these. The gaps in our knowledge are currently being addressed through a research programme which aims to address the points listed in 12 above.

Immature Bearded Vulture, © Sonja Krueger

15) How can people help to protect the Bearded Vulture?

People can dispel the myths that these birds are predators and catch lambs, report sightings of marked birds, report the location of any known nest sites and encourage the use of alternate methods of predator control and alternate options f energy provision.

16) What was your most amazing experience with Bearded Vultures?

Over the past few years, I have had many amazing experiences with the birds. After a long days hike to a nest in the mountains, it is always rewarding to see the birds at the nest- even if you can’t see inside. Watching birds landing and feeding at close proximity is always special. I’ve had the privileged of handling a number of these birds and am always captivated by how large and majestic they are. But the most amazing experience must be sitting camouflaged in the grassland listening to the wind whistling in their wings as the circle a few meters above your head.

Craig Whittington-Jones, © R. Deysel

Craig was born and raised Cape Town. He was an undergrad and PhD student (Zoology) at Rhodes University in Grahamstown.
Since 2000 he has been employed as ornithologist (and herpetologist of-and-on) by Gauteng Nature Conservation.

Although not primarily a raptor biologist, he has however worked quite extensively with the EWT’s Bird of Prey Programme/
Project (and before that with the EWT’s Raptor Conservation Group and Vulture Study Group) on various initiatives including the African Grass-Owl Force which he co-chairs with Geoff Lockwood.

Craig is also involved with monitoring Cape Vulture breeding colonies and assisting with an assessment of the status of Verreauxs’ Eagles along the Magaliesberg ridge in RSA.

He coordinates province-wide large terrestrial bird counts in Gauteng (as part of the Animal Demography Unit’s Coordinated Avifaunal Roadcount Project (CAR) which include Secretarybirds as one of the key target species) and he will will also be involved with the grassland component of BirdLife South Africa’s Secretarybird tracking project.

His current preoccupations are the various initiatives of the Grass-Owl Task Force, a reassessment of the red list status of the African Grass-Owl, and the South African Bird Atlas Project (SABAP2).

1) How large is the range of the African Grass Owl?
In South Africa the range of the species is less than 14 000 km2, where it is largely confined to the eastern half of the country and is most commonly reported for the provinces of KwaZulu-Natal, Mpumalanga and Gauteng. Elsewhere in southern Africa there are surprisingly few records for Mozambique and Botswana, but it was widespread in Zimbabwe (though reportedly not commonly encountered these days) and it has been recently reported for the Caprivi though other older Namibian records have proven erroneous. I have little knowledge of the species further north in Africa, though I am aware of old records including museum specimens from Zambia, Malawi, Rwanda and the Democratic Republic of Congo and the literature indicates that the range extends east through Tanzania, Uganda and Kenya with at least one record for Ethiopia and a few from as far west as Cameroon.

African Grass Owl chicks, © R. van der Westhuizen

2) What are the closest relatives and how do they differ in behaviour and ecology?
The Eastern Grass-Owl Tyto longimembris, which occurs from India through China and south-east Asia to Australia, is considered by some authors to be conspecific with the African Grass-Owl, but in South Africa the Grass-Owl is most closely related to the Barn Owl Tyto alba. While there is some overlap in the habitat and prey (both feed primarily on rodents) of the two species, the Barn Owl is a high adaptable generalist able to exploit a diversity of natural and man-made environments including areas of intensive agriculture and urban sprawl provided that adequate prey and shelter are available. In sharp contrast, although populations of Grass-Owls may occasionally persist on the peri-urban fringe in areas where wetland roost habitat is protected from excessive burning, trampling and general disturbance, this species is far more dependant on natural landscapes than the Barn Owl. Both species hunt mainly at night using a low quartering flight and perches (the latter more so in the case of the Barn Owl probably because of relative availability of perches in their chosen habitats), but whereas Barn Owls may roost in a diversity of natural hollows, caves and crevices as well as in man-made structures during the day, Grass-Owls appear to roost almost exclusively in hollows in rank grass. While few who have visited an active Barn Owl territory at night can fail to have heard its characteristic drawn-out screech, the Grass-Owl appears to be considerably less vocal.

3) What is known about the current population of the African Grass Owl and how has the population changed over the last decades?
This is an area of research that urgently requires considerably more attention. Current population estimates for South Africa are at best little more than an educated guess and there appears to be even less information for the rest of their range. Good population data are only available from a handful of sites in South Africa and all surveys except for those in the Settlers area in Limpopo Province (surveyed in the late1970s) and Suikerbosrand Nature Reserve in Gauteng (surveyed annually since 2009) covered only relatively small areas.

Data from Suikerbosrand NR suggests that population fluctuations between years may be quite dramatic, something that should be expected in an ecosystem where rainfall, fire and grazing pressure can significantly affect cover and prey availability in the course of a single season. Of more immediate concern is the bird atlas data for South Africa (SABAP1 and SABAP2) which indicates an alarming decline in the Grass-Owl’s area of occupancy and reporting rates over the past 30 years or so over much of the species’ range. Data collected from various unpublished sources for the period between the two atlas projects gives some hope that the situation is not as dire as it might appear at first glance, but there can be little doubt that widespread land transformation and inappropriate management of large areas of remaining otherwise potentially suitable habitat have resulted in a population decline over the last few decades.

African Grass Owl habitat in SE Gauteng, © Graig Whittington-Jones

4) What is the main habitat of the African Grass Owl?
In the grassland biome the species typically roosts and breeds in tall rank grass or sedges in or adjacent to seasonal wetlands and along drainage lines foraging more widely over surrounding grasslands and agricultural fields. Elsewhere the species has been reported to utilize a diversity of vegetation types including open savanna with long grass, thorny bushveld, scrub, fynbos, renosterveld, bracken and even karroid vegetation though in most cases the chosen habitat was associated with a wetland of some sort.

5) What is the owl’s main food?
Rodents are the primary prey throughout their range, but shrews, bats, birds, frogs and invertebrates may feature in their diet to a lesser extent. I have yet to find frog or bat remains, but opening pellets can be surprisingly addictive so there is still a chance.

6) Does the African Grass Owl compete with other owl and raptors species for food and breeding places?
In the grassland biome, the breeding and foraging habitat of the more common Marsh Owl Asio capensis overlaps most closely with that of the Grass-Owl. Despite reports of aggressive interactions between the two species, they generally appear quite tolerant of each other and may nest/roost in relatively close proximity in the same wetland. While both species prey primarily on rodents, Marsh Owl pellets frequently include a much greater invertebrate component and when combined with their typically more diurnal activity pattern, foraging competition between the two species may be reduced to some extent. This is nevertheless and interesting topic for further research and Geoff Lockwood has begun looking into it.

The foraging habitat and prey of the African Marsh-Harrier Circus ranivorus also overlap with that of the Grass-Owl, and while the Marsh-Harrier has become rare in Gauteng, there is potential for competition elsewhere within their shared range.

African Grass Owl roost, © Craig Whittington-Jones

7) What are the natural enemies of the African Grass Owl?
As a ground-nesting species there is no shortage of potential predators during the breeding season. While nest failure due to predation appears relatively common (possibly as a result of a human observer creating a convenient path or scent trail to the nest site), the only recorded incidents of predation that I have encountered are by an African Marsh-Harrier on a juvenile/immature Grass-Owl at a roost and the killing of a female and her chicks by what appears to have been a Serval.

8 ) How does habitat destruction and a more intensive agriculture affect the African Grass Owl?
This is a very broad topic especially as the main drivers of habitat destruction vary across the range of the species. My experience lies mostly in the peri-urban environment where it appears that Grass-Owl populations may persist, at least over the short term, within a transformed landscape provided that adequate foraging and nesting/roost habitat remains available. Unfortunately we don’t yet have a good idea of the spatial requirements of the species and even where new urban developments attempt to plan for the inclusion of Grass-Owl habitat in an open space network, the area set aside often proves too small or is impossible to manage appropriately (e.g. fire is an essential tool for removing moribund material and preventing bush encroachment, but is a hazard in a built environment). In a fragmented landscape corridors to other suitable habitat patches are essential for population resilience, but these are designed in the absence of a good understanding of the owl’s dispersal requirements and are likely to become increasingly degraded and fragmented over time.

Mineral extraction is another major driver of habitat destruction since the global appetite for carbon fuels appears inexhaustible and short term economic gains invariably outweigh even the long-term strategic importance of wetland conservation let alone the conservation of owls. While South African legislation compels companies in the mining sector to rehabilitate areas affected by their operations, restoration of natural habitat and ecologically processes is more complex than simply re-vegetating the mine footprint.

Grazing and trampling of wetlands by livestock may be problematic for Grass-Owls where stocking densities are high, but if appropriate rotational grazing schemes are devised the loss of breeding and roosting habitat for owls need not be permanent. This should be an important focal area for agricultural extension officers. In some areas agricultural intensification effectively amounts to habitat destruction e.g. where range-land is converted into large-scale livestock rearing facilities (i.e. feedlots). While such changes may benefit the Barn Owl, Grass-Owls are likely to loose foraging habitat.

Grass-Owls may occur at relatively high densities in areas of intensive crop production provided that breeding and roosting habitat is protected from ploughing, but even where this is the case the wetlands are rarely adequately buffered and degradation as a result of increased nutrient run-off and invasion by weeds seems inevitable. Intensive subsistence agriculture in wetland areas appears to be an increasing problem in-and-around major urban centres in southern Africa where little alternative open land may remain and Grass-Owls are inevitably displaced as a result.

Owl survey, © Craig Whittington-Jones

9) Is electrocution a problem for the owls?
I know of one incident of a Grass-Owl colliding with a powerline, but no electrocution incidents have been reported to me.

10) What other threats do exist for the species?
Roadkills and entanglement on barbed wire fences appear to be the biggest threats after habitat loss and degradation.

11) What gaps in the knowledge about the African Grass Owls do still exist and where should research focus on in the coming years?
The rarity and nocturnal nature of Grass-Owls means that they are relatively challenging to study and as a result we are lacking information on some very fundamental aspects of their biology for example we don’t know what their spatial requirements are, we don’t know why they are present in an area in one year and not the next despite no obvious change in the habitat quality, we don’t know much about their dispersal abilities either in natural or fragmented lanscapes or how readily they re-colonize areas after a disturbance (e.g. fire).

Establishing the foraging requirements of the Grass-Owl is critical for effective conservation planning in areas that are threatened by habitat destruction whether caused by urbanization, mining or some other factor. However, since most Grass-Owls occur in rural areas we also need to determine the appropriate use of fire and grazing as habitat management tools in each biome and develop practical extension tools for use by commercial and subsistence farmers. Further research is also required into road design and maintenance in order to reduce roadkills.

Owl survey, © O. Katumba

12) Are there any conservation programs for the species?
In the 2009 the then Bird of Prey Working Group of the Endangered Wildlife Trust established the African Grass-Owl Task Force. This task force comprises Grass-Owl enthusiasts from a diversity of fields and draws on their expertise to conduct research, gather information and create awareness in order to further conservation of the species. Examples of such initiatives include ongoing research into the spatial requirements of the Grass-Owl, targeted surveys and gathering of historical data in order to map Grass-Owl distribution for inclusion in provincial conservation plans, and the collection of roadkill data for the identification of mortality ‘hotspots’. To date the focus has been on southern Africa, but participation from elsewhere in the species’ range would be welcomed.

13) What other species of birds and other animals could benefit from such conservation programs?
Habitat conservation is a critical component of the task forces’ work and the identification and conservation of wetlands and associated terrestrial foraging habitat and corridors that are of a suitable size and managed appropriately to ensure the persistence of Grass-Owls will benefit a diverse suit of species that are dependant on similar habitat including the African Marsh Harrier, Serval, Giant Bullfrogs and many other rare and common species.

Young in hacking cage, © R. Deysel

14) How do you see the future of the African Grass Owl?
For various reasons I don’t hold much hope for the persistence of those Grass-Owl populations in peri-urban areas, but there is room for optimism elsewhere:
1. Regional spatial conservation plans are available for much of the species’ range in South Africa; 2. All levels of government are becoming increasingly aware of the importance of wetland conservation in a water scarce country; 3. Landowners that I have encountered are generally positive about conservation of biodiversity and would probably be receptive to advice on habitat management provided that the realities of their need to make a living from the land were recognized.

15) What was your most amazing experience with the African Grass Owl?
While I feel I should be describing my first Grass-Owl sighting (equally unexpected for me and the owl) or my first discovery of a nest full of downy chicks, the most amazing experience has actually been the response from volunteers. These are not mere twitchers keen for a lead on a tricky tick, but well known names in the raptor and conservation world as well many other less renown but equally dedicated enthusiasts who have generously shared their knowledge and experience and repeatedly donated their time to facilitate and promote research and conservation of the species.

A Crowned Eagle attending a chick

Results from the project may have implications for raptor conservation in the wider region.  For example, hunters from the village of Batoke, bordering the Mount Cameroon National Park, openly admitted to hunting crowned eagles (Stephanoaetus coronatus).  They also suggested that encounters with crowned eagles had reduced during their career (as long as 15 years) and they now expected to encounter only one eagle per annum.  As in the Ebo forest, hunters here are familiar with crowned eagle vocalisations and with the techniques used to mimic crowned eagle calls.  This is worrying and suggests that the technique is used throughout Cameroon’s forest belt, as Mount Cameroon is distant from the Ebo forest in both cultural and logistical terms.  Although crowned eagles are likely to be among the most vulnerable species because of their low reproduction rate, more common species such as palm-nut vultures (Gypohierax angolensis) and gymnogenes (Polyboroides typus) are also hunted regularly (see photo).  It appears that any medium to large raptor is targeted when the opportunity arises and it is essential that this off take is measured quantitatively so that sustainability can be assessed.

Mammal research is also developing in the Ebo forest and intensive transect surveys are now being carried out.  Several field assistants received raptor recognition training in June 2011 and now record crowned eagle vocalisations when walking transects.  This valuable data will allow us to begin monitoring crowned eagle populations in the Ebo forest and to detect changes over time.

The single crowned eagle nest located in 2009 was monitored throughout 2010 but remained unattended and had disappeared by July 2011.  This was disappointing but we did observe a pair of crowned eagles displaying above our base camp (Bekob) in July 2011 and are probably nesting near by. Hunting has decreased generally in the Bekob area as a result of the EFRP’s presence and this may have a positive affect on raptors in the local vicinity, as has been observed with primates.

A persecuted Harrier Hawk (gymogene)

We hope to further train local field assistants to identify raptors in the field by both site and sound and increase monitoring of other species in the future. The Ebo forest is undergoing the transition to National Park status and although the process is slow, this will undoubtedly be positive for raptors and their conservation in Cameroon.

More information about the Ebo Forest Research in Cameroon can be found at their website.

Andrew Jenkins is one of the most prominent raptor biologists in South Africa and has been studying Peregrine Falcons on the Cape Peninsula for more than twenty years. His interest in falcons also extends to other species and he published the first confirmed records of the presence of Taita Falcon in South Africa in the 1990’s and has been involved in the surveying of this population of the species for many years. Andrew established a raptor research programme (Western Cape Raptor Research Programme) at the FitzPatrick Institute, University of Cape Town and has been instrumental in setting up numerous long-running projects. These include population studies on the Rock Kestrel, and Black Sparrowhawk, pesticide studies of African Fish Eagles, behavioural ecology studies of Black Harriers and colour marking studies of Black Eagle. He is also one of the foremost experts in terms of the impact of energy infrastructure on raptors and other birds and currently consults extensively in this regard, in particular with regard to the many wind-power developments planned in southern Africa. Andrew is also the author of many scientific and popular publications and was this year honoured with the Endangered Wildlife Trust Birds of Prey Programme’s Raptor Conservationist of the Year Award.

André Botha

Taita Falcon perched, © Alan Kemp

1) What is known about the status of the Taita Falcon across Africa? How many birds are there?

The Taita Falcon occurs down the eastern half of Africa, as far west as the Rift Valley, as far north as southern Ethiopia, and as far south as north-eastern South Africa. This might seem like quite an extensive range, but it is very patchily distributed within this area, in a way that is not presently well understood. Like the Peregrine, it seems to go for habitats that particularly favour it’s cliff-nesting and bird hunting habits – high cliffs in bird-rich areas – but it seems to be much more picky than its bigger cousin. The net result is that its global population is manifested as small, scattered pockets of localised ‘abundance’, sometimes comprising only 1-2 breeding pairs, separated by 100s, even 1000s of kilometers of apparently unsuitable habitat. This impression of patchiness in its distribution may be exaggerated by problems with detecting this small, fast-flying but relatively sedentary species in habitats that are difficult to access, and it has probably been overlooked in some of the less explored areas of the sub-continent. Word has been spreading recently about a number of pairs of Taitas residing on remote inselbergs in the Niassa area of far Northern Mozambique, and we’re hoping to get up there soon to check this fascinating area out.

How many? Well there are substantially fewer than 50 known breeding pairs of TFs on the planet. The jury is out on the actual population, but it is certainly well below 1000 pairs, and probably less than 500 pairs.

2) Has the population changed during the last decades?

We held an informal workshop on TFs at the last PAOC gathering in 2008, at which we tried to collate what we know about numbers and population trends, and figure out what we needed to do to improve our understanding of the status and conservation of this species. An important (if disappointing) conclusion was that we don’t really know enough at present to say anything definitive. However, information from Zimbabwe was cause for concern. The late Ron Hartley, together with an excellent team of local Taita Falcon enthusiasts (many/most of them falconers) spent years studying this species in Zimbabwe, and most of our current knowledge of the biology of the Taita Falcon stems from his surveys and observations of the Zim population. I think Ron knew of up to 16 nest sites in Zimbabwe, and suspected as many as 50 pairs were resident in the areas he and his team frequented. Since Ron died, Neil Deacon and others have done their best to keep tabs on at least some of the Taita sites in Zimbabwe, and their take on the current situation there is not encouraging. A high percentage of Ron’s known territories are no longer occupied, and even the long-established stronghold at the Batoka Gorges below the Victoria Falls has apparently dwindled from six known pairs to only one, and the species reportedly hasn’t bred successfully there for over a decade.

Similarly concerning information has come out of Uganda, with the four pairs reported from Mt Elgon in the 1980s apparently no longer there. The data to hand are by no means conclusive, and survey effort was almost certainly greater in the past than what is being brought to bear now, but indications are that the Taita Falcon may have decreased in some areas of its very sparse central African range. In contrast, we have done some quite intensive searching for these birds in South Africa in the last 5-6 years, and have managed to bump our known population up from two pairs (the first of which was only discovered in the late 1980s) to eight. In fact, we have found enough pairs to question whether these birds could possibly have been missed in raptor surveys conducted by some pretty heavyweight observers 30 years ago. The Taita Falcon is not the sort of bird that I would expect to exhibit quite sharp changes in distribution and abundance, but some of the evidence to hand, particularly from South Africa, suggests that such fluctuations might occur.

3) What is the preferred habitat of the species?

Good question! It is an obligate cliff-nester, and certainly likes big rock faces, although it is by no means restricted to only very high cliffs. It is also linked somehow with woodland habitats, with a penchant for dry woodland, and an apparent dislike for cliffs overlooking forest. Beyond that it’s difficult to say. My personal belief is that the Taita Falcon is a highly specialized predator that depends on habitats with a very particular structure and/or avifauna in order to make ends meet. Quite what that habitat structure might be I’m not at all sure. Ask me again in 10 years time!

Typical South African Taita Falcon habitat, © Andrew Jenkins

4) What is the preferred prey of the Taita Falcon?

Small birds. The literature would have you believe that it is a major predator of aerial insectivores (swallows, martins and swifts), and this is surely true in some areas, but has not really been our experience in watching Taitas in South Africa. We spent some time last summer watching pairs provisioning newly fledged young. They were under pressure to perform and, in some cases at least, operating on cliffs with thriving swift and swallow populations on and around them. We saw lots of hunting, but not one confirmed strike at an aerial insectivore, and only one delivered prey item that could possibly have been a swift. We struggled to identify what they caught and brought onto the cliffs, mostly because each item was so small and so rapidly processed. Red-billed Quealea came up a few times (even though we saw none in the local environment), and a possible Tambourine Dove. I’d be surprised if they took anything bigger than 80g with any regularity.

5) Is there a difference in prey size taken by males and females?

I really couldn’t say for sure, but the species is certainly sexually dimorphic enough to suggest that there is, and we’ve indications of this at the nests we’ve spent time watching in SA.

6) How do the birds hunt? Do they also hunt in pairs?

They are very fast and, like other large falcons, use speed as their primary means of surprising and catching their prey. They have an extremely chunky build, very short tails, and very hard, inflexible plumage. As such, they are built for high speed operation, even more specialized in their construction than the Peregrine. I’m not sure that they fly faster than Peregrines, but they certainly exceed them in terms of the frequency with which they fly fast, which is pretty much all the time!

Taita Falcon perched, © Alan Kemp

I think they occupy very small foraging ranges, but they can work those small areas very hard. Much of their chunkiness comes from massive pectoral muscles, which they use to generate a very high wingbeat frequency, getting them from A to B in double quick time even when there is no wind to hold them up. When the wind is blowing, to me they become quite buoyant flyers. Clearly they have a very high wing loading relative to their size, but in absolute terms they can use even moderate winds to huge advantage. They have a very interesting wing shape, with shortish outer secondaries just like a Peregrine, but then unexpectedly long middle primaries. The net result is a curiously blunt-ended, boomerang like outline, which must have some aerodynamic significance – perhaps it confers more forward thrust on the downstroke of the wingbeat? Coupled with an almost non-existent tail, the Taita is certainly a departure from the standard large falcon design. Understanding the function of this odd shape may be key to understanding the constraints within which this bird operates, possibly unlocking the secrets of its weirdly patchy distribution?

Given what I’d read about them before I started watching them, I expected Taita Falcons to hunt mainly in the high, open sky. This is where swifts like to ply their trade, and I figured the Taitas would get up there with them and hunt them down. This might well happen, and certainly the bird has the look of an effective swift hunter, but the Taitas we’ve watched on the Mpumalanga escarpment seem to hunt the woodland below their cliffs much more often than the wide open spaces in front of them. They are incredibly adept at snatching small birds from just above the tree-tops, in a way that I have never seen Peregrines or Lanners even begin to contemplate.

Yes, they hunt in pairs, but I would be surprised if they did so in a truly cooperative way. From the little I’ve seen, just like Peregrines, members of Taita pairs target the same bird at the same time, and may increase their chances of success in doing so, but there is little or no division of roles, and no sharing of the spoils afterwards.

7) What is the average breeding success of Taita falcons?

Not what you’d expect in a bird of this size. All other things being equal, allometric theory would predict that the much smaller Taita would lay larger clutches of eggs and fledge bigger broods of young than either Peregrines or Lanners. In reality this is not the case. The data are few, but four egg clutches are no more frequent in Taitas than in Peregrines, and they probably fledge smaller broods on average than Peregrines, and appreciably smaller broods than Lanners. So even though they are much smaller than sympatric congeners, they seem to be slightly less productive.

8 ) Is there competition with other raptors, for example Peregrines?

All indications are that they may struggle to co-habit with other, larger falcons. Certainly Ron Hartley noticed some Zimbabwean Taita sites apparently turning over to Peregrines or Lanners, and Kit Hustler noted how the Taitas in the Zambezi gorges near Victoria Falls were subordinate to Peregrines, and moved their nest ledges in response to changes in the location of Peregrine sites. However, in terms of their respective resource requirements, I think that there is probably quite good niche partitioning between the three species, and given the marked size difference between Taitas and the two bigger birds, I’d say there was less scope for active competition between them and either Peregrines or Lanners than there is for competition between Peregrines and Lanners. I suspect that the problem for the smaller species may be more about domination and possibly even predation by the larger falcons, than it is about competition per se.

9) What is known about movements of the falcons and dispersal of juvenile birds?

That’s an easy one – nothing. I think it’s probably fair to say that territory-holding adults are strongly centred on their nest cliffs and the immediate surrounds throughout much of the year. There must be some relatively long distance dispersal of young birds and non-breeders in the ‘floating’ population in order for the various small populations to remain genetically in touch, and records of injured birds being picked up a long way from any known nesting areas support this notion.

10) Is the species affected by pesticides?

As a close relative of the Peregrine – a species that seems particularly adversely affected by pesticides and chemical pollutants, there is always the chance that the Taita Falcon could be susceptible to these substances too, and we would be remiss in not considering this factor in our efforts to conserve the species. However, given that Taitas typically use habits situated away from intensive agriculture, and probably take prey less likely to ingest toxins than Peregrines, they may be less easily exposed to chemical contamination.

2010 SA Taita survey team (from the left: Anthony van Zyl, Andrew Jenkins, Lucia Rodrigues, Alan Kemp), © Andrew Jenkins

11) Are the birds illegally hunted for falconry?

I’m not sure that ‘hunted’ is the right term – harvested maybe? – and while there have been a couple of iffy incidents at one nest site in South Africa (and doubtless elsewhere too), my perception is that the Taita is not a species in high demand by serious falconers. It is too small and too specialized for classic falconry. While there seems to be some interest in trying Taitas as falconry birds (and this has been done to a limited extent quite legally in both Zimbabwe and the US, using captive bred stock), and perhaps a little more interest in captive breeding and hybridizing the Taita with other, larger falcons, I don’t think falconry – legal or not – poses a significant threat to the conservation status of the species.

12) What other threats do exist for the species in Africa?

I doubt that there are any clear and overriding factors. Rather, the very sparse nature of the Taita’s distribution, its very particular habitat requirements, and its small aggregate global population, make it vulnerable to a wide variety of factors on a localized basis. For example, small populations of fewer than 10 pairs may be affected by a highly location-specific variable – e.g. disturbance by adventure tourism at Victoria Falls, habitat loss to rural development around the Mpumalanga escarpment or to elephant overpopulation in the Zambezi valley, or pollution or impoundment of key river systems. Any such mechanism could quite quickly render previously high quality habitat unusable, resulting in localised extinction of the species.

13) What needs to be done to secure the future of the Taita Falcon?

I’m a great believer in the need to understand a species before planning a strategy for its conservation; in knowing how many individuals or pairs there are out there, getting a bead on current numerical trends, and developing a working understanding of the key resources which underpin the birds’ survival. Right now, I’d say that we are generally ignorant of most of these aspects of Taita Falcon ecology and biology. We need to learn more about the species, its requirements and its problems before we can hope to secure its future.

14) Are there any conservation projects for the Taita Falcon?

At the moment we are trying to learn more about the Taita population in South Africa – we (the South African Taita Falcon Survey Team – core members Anthony van Zyl, Lucia Rodrigues, Alan Kemp and myself) conduct annual surveys of the breeding pairs we’ve located in the Mpumalanga escarpment area, survey the area for new pairs, and we have recently started looking at breeding success, diet, hunting behavior and provisioning rates. To the best of my knowledge, this is the only funded research or conservation project on the species underway at present, and it is very small scale – amounting to not more than a couple of weeks of field time annually. In the past, This work has been sponsored by The Peregrine Fund, as well as by the African Bird Club, the Endangered Wildlife Trust, Birdlife South Africa and Glendower Whisky. We recently signed up with BirdLife SA/International as Species Guardians, and hope to tie our work with more opportunistic work being done by Simon Thomsett in East Africa, Neil Deacon and others in Zimbabwe, to develop a more Pan-African picture of the Taita’s status.

15) Can bird watchers visiting Africa help, for example by sharing their observations of Taita Falcons outside the known territories?

This is a difficult bird to see, and there are issues with identification, but any reliable Taita Falcon sightings, pretty much from anywhere except the very best known sites for the species, would be extremely useful.

16) What was your most amazing experience with Taita Falcons?

There have been a couple of memories that stand out. I guess the main reason I love watching falcons is the incredible speed and precision of their flight, and I remember watching at a Taita site near Blyde River Canyon with the rest of the SA survey team a few years ago wher we saw a great example of this. The birds we were monitoring were incubating at the time and the female was tucked out of site at the nest ledge. It was late in the afternoon and there was some weather blowing in onto the escarpment, the horizon looking dark and stormy, and the wind rushing urgently over the cliff-top. The male Taita was on a mission, riding the coming storm with irresistible energy and sizzling velocity. In an instant he transformed himself from a small, dense speck hanging in the sky, pinned against a curtain of grey looming over the Drakensberg crags, to a blurred flash of russet, scorching across the rock face then surging upwards again into the brooding heavens. He repeated this circuit several times. As observers, all we had to do was stand still and follow him in our binoculars as he described giant arcs in the air above and below us. And yet we struggled, left dazed and confused, losing and searching for him again and again as he jetted on his way.

Another memorable moment occurred later in the breeding season. Anthony van Zyl and I had hiked up under a known site in early December to check breeding success. We had waited on the slope below the nest cliff all morning in thick mist and rain, hoping that the cloud would lift and our patience would be rewarded. Around midday the weather brightened, and quite quickly we had a view of the cliff. As visibility steadily improved the Taitas came to life. It seemed that they had been waiting as expectantly as we had, and the scratchy whining of at least two newly fledged youngsters became more and more urgent. In response, the adults got airborne and started hunting, soaring in front of the cliff which was now completely clear of cloud. In the next 40 or so minutes we saw six strikes, most if not all of which were made at small passerines over the dense woodland immediately below the cliff, and all of which were successful and resulted in prey deliveries to the brood. There was absolute chaos on the cliff, with the two chicks receiving an obscene glut of food. At one stage we watched a youngster mantling over her second meal in ten minutes, as her father tried vainly to ply her with a third! We learned for ourselves that day what others have noted before us: that under the right conditions the Taita is a highly efficient hunting machine. And, as others have done before, we were left wondering why it is not more widespread and successful in the Afrotropics?

Alan Njuguna performs his "I believe I can fly" in praise of Vultures

In Kenya the event is organised by the Raptor Working Group of Nature Kenya and this year’s event was hosted by Ol Pejeta Conservancy in Laikipia District.  This third event was attended by 120 school kids from seven neighbouring primary and secondary schools.  For a ‘vulturephile’ you couldn’t beat the entertainment, rap songs about vultures, dances and poetry, all capturing the unique characteristics and importance of vultures. The kids got an up close look at some vulture skins and learned from members of the Raptor Working Group about special adaptations of vultures.  We encouraged the students to show off their artistic talents by entering an art competition with the theme ‘the role of vultures in the cycle of life’.  Twelve of the top artists were awarded prizes during the event.

A Masai dance in praise of vultures

Guest speakers challenged the students to spread the word about the importance of vultures and not to engage in practices that are harmful to vultures, particularly poisoning wildlife.  They also drew parallels between Kenyans’ negative attitudes toward wildlife and its decline. Speakers included representatives from Kenya Wildlife Service, BirdLife International, Laikipia Wildlife Forum, National Museums of Kenya, Wildlife Clubs of Kenya, and Nyahururu Bird Club.

Dr. Munir Virani of the Raptor Working Group and The Peregrine Fund presented our hosts with a beautiful vulture painting that was made during a previous IVAD event by Watoto kwa Kwetu Trust.  All the attending schools took home posters about the importance of vulture conservation and copies of Komba magazine, a children’s publication focused on conservation and produced by Wildlife Clubs of Kenya. In addition, students in all participating schools will receive copies of the colouring book, ‘African vultures’, produced by Raptor Working Group member Martha Nzisa. Finally, in honour of the late Kenyan Nobel Laureate, Wangari Maathai, students planted 150 indigenous trees within the conservancy.

This year’s event was a resounding success and once again the students surprised us with their knowledge and excitement about vultures. Through contacts made during the event, we will continue to spread the word about the importance of vultures to schoolchildren throughout Kenya by collaborating with education officers from the Laikipia Wildlife Forum and Wildlife Clubs of Kenya.

All the participants at IVAD 2011 after planting trees in honour of Kenyan Nobel Laureate Wangari Maathai

Funding for this year’s event was graciously provided by the N.E.W. Zoo (Wisconsin, USA).  Additional support came from Ol Pejeta Conservancy and The Peregrine Fund.  The organisers also thank Kenya Wildlife Service, BirdLife International, Laikipia Wildlife Forum, National Museums of Kenya, Wildlife Clubs of Kenya, and Nyahururu Bird Club for their support of the event.

Darcy Ogada is Assistant to the Africa Programs of The Peregrine Fund and is also Chairperson of Nature Kenya’s Raptor Working Group.

Immature Short-toed Eagle

Mellone, U., Yáñez, B., Limiñana, R., Muñoz, A.R., Pavón, D., González, J.M.,
Urios, V. & Ferrer, M. 2011 Summer staging areas of non-breeding Short-toed
Snake Eagles. Bird Study DOI:10.1080/00063657.2011.598914

The importance of the non-breeding fraction of raptor populations for conservation is well recognized, but little is known on the behaviour of these “ghost” birds, especially in migratory species. The Short-toed snake Eagle Circaetus gallicus is a migratory raptor that breeds in Europe and northern Africa, spending the winter in sub-Saharan Africa. Through satellite telemetry, a group of researchers led by the Estación Biológica Terra Natura (University of Alicante) and by the Fundación Migres recorded data of seven summering events belonging to six individuals hatched in Spain. Immature Short-toed Eagles left their wintering Sahelian grounds by mid-April, and after crossing the Sahara desert, the birds settled in Morocco and Algeria, thus not returning to Europe in their second nor third summer, and using one-three different staging areas for each summering. The eagles may have found suitable foraging areas along the migration route, where intraspecific competition was probably lower than at the breeding grounds, interrupting the migration journey to stay in these areas.

This study pinpoints that conservation of migratory long-lived species should not be solely focused in breeding and wintering grounds, but also should consider those events occurring in non-breeding summering areas. Download the complete paper here:

http://www.wildphoto.it/Mellone-et-al_S-Teagles-summer_BirdStudy.pdf

This article was provided courtesy of Ugo Mellone and his co-researchers.

I first met Alan years ago when he was the curator of birds at the Pretoria Museum. I was just beginning field and museum work on the African raptor field guide. After a few days of studying raptor specimens, Alan invited me to join him for a week of field work in Kruger National Park. Alan had already published many articles reporting his extensive raptor field work. During this week I was able to learn a great deal about African raptors from him, as well as study and take photos of them in person.
Alan was born and raised in Zimbabwe (then Rhodesia) and has always been interested in natural history, including practicing falconry. He received a PhD at Rhodes University, South Africa and first worked on raptors for and with Dr. Tom Cade for three years in the Kruger National Park. He later spent 32 years as ornithologist and curator of birds at the Transvaal Museum in Pretoria, South Africa. He and his wife Meg coauthored ‘Birds of Prey of Africa and its Islands,’ a mini handbook still in demand. Since retiring from the Museum, he has worked as a wildlife consultant. His main research interest is hornbills in Africa and Asia, but he has always included studies on raptors wherever possible, including recent raptors surveys in South Africa.
I have had the good fortune to spend much time with Alan over the years, both field and museum time, and every such time I learned more about African raptors. I’m sure that you and I will very much enjoy this interview.

Bill Clark Harlingen, Texas USA

All images in this interview taken by Alan Kemp or Keith Begg.

Adult Martial Eagle in Fligh. Krüger NP.

1) What is known about the current status of the Martial Eagle in South Africa and other countries?

The Martial Eagle is designated as Near Threatened in the 2011 IUCN and BirdLife International Red List over its total African range of c. 750 000 sq.km, but as Vulnerable in the official South African Red Data book. There is also concern for the species in Zimbabwe and Swaziland.

2) How has the population developed over the last decades?

I am only familiar with the status of the species in South Africa, where it has declined over the last few decades, not obviously in range but probably by about 20% in numbers. It occurs naturally at low densities, but in some areas it is now rare or absent.

3) Is there a difference between protected areas and non protected areas?

Within South Africa and Botswana there is evidence that it is recorded more in large conservation areas than in unprotected areas, most notably in the Kruger National Park and the Kgalagadi Transfrontier Park within South Africa.

Adult Martial Eagle perched overlooking savannah bushveld habitat, near Skukuza, KNP, 1990s

4) Is persecution still a serious problem for the Martial Eagle?

Persecution, direct and indirect, is still a cause of mortality in South Africa and Namibia, especially in areas of small livestock (sheep, goat) and game farming. Direct shooting and trapping, and indirect poisoning appear to be the main factors, but various education and awareness programmes in South Africa are having an effect in some areas.

5) How does electrocution affect Martial Eagles? What can be done to reduce mortality?

Electrocution is a cause of mortality in South Africa, but probably not a major one. Lower voltage rural lines, with the live wires close enough together to be touched simultaneously by such a large eagle, are the main culprit, but some of the deaths also result from collision with the wires. At the same time, the tall pylons supporting high voltage lines offer nesting sites in more open habitats. The national electricity supply agency works closely with conservation NGOs to rectify problems and encourage safe nesting. Problems with power lines are expected to be less in less developed countries with fewer supply lines.

Trapping adult Martial Eagles for ringing and/or wing-tagging for research, KNP, 1990s

6) What other threats do exist for the Martial Eagle?

An import threat, especially in drier areas, is drowning in open water reservoirs. This can be avoided by floating an exit structure (ladder, log) to enable birds to clamber out of the sheer walls, but requires the necessary education and awareness of landowners. Martials can live for long periods without drinking, although they do sometimes drink and bathe when water is available, but most drownings occur in arid areas where the need to drink or bathe may be more frequent.

Despite all these known causes of mortality, the primary threat to this large eagle in South Africa, and probably elsewhere in Africa, is almost certainly conversion or reduction in the prey-carrying capacity of its favoured habitats. Conversion of land to agricultural crop- and pasture lands, or to dense small-hold and residential areas, effectively excludes the species, while extensive herding and ranching lowers the carrying capacity of natural prey animals, especially when stocking rates are excessive.

7) What is the preferred habitat of Martial Eagles?

The most favoured habitats are open savannas, with a mix of indigenous trees, large and small, bushes and areas of open grassland. Such a diverse mosaic of plant forms, and the ecotones they produce, support both a high diversity and density of prey species. Martials extend readily into more open semi-desert habitats, and even into desert along wooded watercourses, but at a lower density. Wherever they occur, they require large trees (or pylons) as nest sites. They do not occur in more densely wooded habitats, such as parts of Mozambique and Tanzania, nor in forest habitats (where the large African Crowned Eagle is most common), and it generally avoids very broken terrain (where Verreaux’s Eagle and its main hyrax prey predominate).

8 ) What is the main food of Martial Eagles?

A wide variety of animal prey is captured by this large and powerful eagle, predominately vertebrates of 1-4 kg in mass, with the most frequent items varying from region to region depending and availability and abundance. Gamebirds, viverrids, squirrels and large lizards are often important prey items, but birds as large as Kori Bustard, mammals as large as young warthog, impala or baboon, and monitor lizards are taken at times. Most individuals do not take livestock, even in farming areas.

Trapping adult Martial Eagle for ringing and/or wing-tagging for research, KNP, 1990s

9) Do Martial Eagles compete with other raptors for food or nesting places?

Martials often occur in habitats that support a variety of other predatory birds, especially in extensive areas of natural habitat and/or conservation protection. Their main competitors of similar size are usually separated by habitat preference, such as African Crowned Eagle (forest), Verreaux’s Eagle (rocky habitats, cliff nesting) and African Fish-Eagle (waterways), or by hunting behaviour (Secretarybird, Ground-Hornbills) but where their ranges overlap there are sometimes competitive encounters, mainly about prey that one or other species has flushed and/or captured.

Other predatory birds that interact with Martials include those that regularly pirate prey (Tawny Eagle, Ground-Hornbills), and those that sometimes take over their vacant nests (various eagle and vulture species).

In general, Martials are the largest, strongest and best-adapted predator in this preferred habitat, and so competition is usually low.

10) What is the typical hunting technique of Martial Eagles?

Martials hunt from a perch, usually in a tree but sometimes on a rock or even on the ground. However, their main hunting technique, making use of the long broad wings and expert soaring ability, is to soar over their extensive home range and then descend on prey spotted below, either in a long shallow dive or, less often, a steep fast stoop. Rarely hover during strong winds when hunting, but much less so than the similar-looking Black-chested Snake-Eagle. Sometimes lands after an abortive strike, and then waits at perch for a second chance. After killing large prey, may perch nearby and return at intervals to feed, exceptionally for five days.

11) Do Martial Eagles also feed on carrion?

They will pirate prey from other predators and even come to feed on carrion, but not on a regular basis. Some of the instances reported as livestock kills are known to be actually attraction to carrion.

12) How often do Martial Eagles breed and how many eggs are usually laid? Do sometimes more than one chick fledge?

A Martial Eagle female only ever lays a single egg per clutch and so raises only a single chick at a time. Laying commences usually during the driest season (e.g. April-June in southern Africa), and pairs often attempt to breed in successive years. As many as one 30-50% of pairs may not breed in a given season,because conditions are unsuitable and/or a juvenile is still being raised, and overall pairs fledge on average about one chick every two years. The long nesting cycle (c. 50 days incubation, 100 days nestling, 3-4 months post-fledging dependence) means that nesting starts when prey visibility is best and continues into summer when prey numbers are highest.

Friend Richard Harland with chick at base of nest tree.

13) What is known about the dispersal and movements of Martial Eagles, especially the juvenile birds?

Adult breeding pairs appear to be resident and sedentary once they have established their large territories (c. 150 sq.km in wooded savanna to 250 sq.km in semi-desert). In areas of good-quality contiguous habitat there may be few dispersal sites for juveniles/immatures during the c. 6 years before they attain mature plumage (as in several large conservation areas), and so they wander widely (although exact details are sparse) and predominate in accidents in what are probably less productive marginal habitats.

14) What natural enemies do Martial Eagles have, for example can Leopards or Baboons be a threat to the young in the nest?

Being so aerial, large and powerful, for Martials few instances of predation are reported, even at nests, and most known mortalities are due to accidents. Baboons are diurnal and likely to be driven away, but leopards are nocturnal and might surprise and adult/chick on the nest. Most nest failures by known ‘predation’ involves egg- and/or chick-collectors, or other human persecution.

15) Do you know of any conservation projects for the Martial Eagle?

There have been several field studies of Martials in South Africa, Namibia, Zimbabwe and Kenya that I am aware of, mainly in large conservation areas but also in livestock and other farming areas. These have supplied some of the details on biology that are necessary to organise effective conservation management strategies, but in the end depend on the priorities and will of the residents of the countries within the species’ range. I am not aware of any comprehensive current projects that specically target this species.

Martial Eagle chick on nest in mountain 'acacia' Brachystegia glaucescens with lake shore in background.

16) What should be done to secure the future of Martial Eagles in Africa?

The primary effort to secure the future of this species in Africa is to maintain as many large areas of pristine, or near-natural habitats as possible. These would supply a productive basis for the population as a whole, and probably ensure that increased mortality from various anthropogenic effects do not precipitate a general decline. In practise, this requires local conservationists to secure and protect whatever natural habitat they can, within the realities of the human requirements within their region. How this is achieved in the face of human populations growing in size, affluence and ambition, and divided into diverse ethnic and political units, remains the real challenge.

17) What other raptors would benefit from such conservation measures?

African savannas support a high diversity of raptor (and other animal and plant) species, so ensuring the protection of viable populations of an eagle with such large spatial requirements as a Martial Eagle will inevitably protect a high level of biodiversity. For example, in the 20,000 sq km Kruger National Park of South Africa (now doubled in area as a transfrontier park) there are an estimated 130-150 breeding pairs of Martial Eagles, among a total raptor community of c.70 recorded species, and where, with luck, one can see 26 species in a single day.

18) What was your most amazing experience with Martial Eagles?

While I was busy ringing a large Egyptian gosling near a small dam, an adult female Martial Eagle passed high overhead at a height of about 200 m above ground. I released the gosling once the eagle was at least 1 km away and, as it waddled off to the water, the eagle banked, made a long 2-part stoop, first away and then back, and ended with a rushing attack just as the gosling reached the safety of the water. The distance at which it spotted the potential prey, the rate of its attack, and the spectacle of the near-miss at close quarters was unforgettable.

Crowned Eagle pair with chick, © Simon Thomsett

Movements

To my knowledge no population of Crowned Eagles migrates, or has seasonal movements. One might expect juveniles to move after foraging parties and disperse widely, but not adults. They appear to be very sedentary, but appearances can be deceptive and further study may show unexpected swapping of spouses, hedge hopping, cuckoldry and large movements of some individuals. In the housing estates of Tai, urban lifestyles may be expected! Leslie Brown once noted an adult Crowned Eagle after a rain storm in Tsavo on a small and dry hill. It must have been on passage. I have seen an adult Crowned Eagle in a sparse river bed at Lewa Downs far from its usual habitat and assumed it was just passing through. None had visited the area for years, and none did so since, so it may have been on passage. Juveniles can appear in bizarre places, such as the Nairobi Golf Course near the city centre but this is not evidence to say that they are living there, and thus prospering (as was the suggestion).

Annual or Biannual reproduction
One might expect that the ‘forest’ eagle reproductive recruitment is higher than that of the ‘bush’ eagles because of greater competition and presumable greater risk of violent death. If better and more assured nutrition is a factor then again one would expect the ‘forest’ eagle to produce more. Unlike the ‘bush’ eagles they do not share their territory with Martial, Verreaux’s and African Hawk Eagles…but with each other. There is no greater a direct competitor than one’s own species. Their close proximity and the vicious engagements they must surely endure from neighbouring pairs means that it is likely that mortality from territorial combat is higher than with ‘bush’ eagles. The fact that the ‘forest’ eagle have a particular taste for adult male Red Colobus, the ignoramus bully with forearms longer than mine, also makes one ponder if they get wounded by prey more than the ‘bush’ eagles. Despite being later proved wrong when I caught a couple of recently fledged youngsters in Tai that looked like second year birds I kicked around an idea with Susanne and Guy Rondeau that they also matured quicker, because they had to. In a more violent world maturing quicker and breeding faster would be beneficial and perhaps it may happen. That one chick per annum has been recorded in similar South West Ugandan forests (which sent ripples of anxiety through Crowned Eagle lovers the world over) could be explained as a one off, premature death of previous chick, or that locations of endless and stable bounty could turn out more young. It may be one of those things that can occur in super-productive and perhaps more violent forests. Annual breeding for a species with so long a reproductive cycle must require great effort only possible or necessary in an area with food abundance and high mortality.
In captivity Crowned Eagles could breed each year and I have deliberately accelerated or delayed them by keeping their chick with the pair. A begging youngster is a definite libido crusher. Once removed (after at least 4 months) sexual activity quickly returns. Returning the chick once mating and nest building commenced saw the parents divided with the adult male being attentive and the adult female being aggressive. In this case the chick was a female, and so it could have been considered sexual competition. It is unwise to assume that the Crowned Eagle (or any other) is an obligatory biannual breeder irrespective of extraneous considerations. If the chick has dispersed or died earlier than usual there is nothing stopping pairs recycling in equatorial and tropical Africa. But I understand that there is enough evidence to suggest that the breeding cycle is too long for a usual, temperate world (South African) annual breeding cycle.

Hunting methods
I have had unique opportunity to watch Crowned Eagles hunting in trained and wild conditions. I have trained some 15 Crowned Eagles over the years, mostly captive bred, but some passage and haggard birds as well. I must have seen a few or more hundred kills, mostly hares and springhares (taken at night down a spotlight) and vervet monkeys during the day. The wild ‘taken’ (all rehabs) adult birds would, one must assume, replicate the same hunting methods they utilise in the wild if given the chance. I noted among their repertoire of techniques blind approaches to prey, using contour and tree trunks to hide their attack. Monkeys and hyrax feeding on limbs in full view causes the eagle to freeze and lengthen, until one walks with it behind an obstacle. Only then does the eagle flare its facial disc, crane its neck and show signs of intense excitement. When sure that all members of the prey are unable to see its approach it launches its attack straight at the individual most likely to be the greatest surprised. Whipping around the tree trunk at the last second it either connects with the prey, or sends the whole group into disarray and panic and misses. The extreme interest shown in prey that goes behind an obstacle is common with all Crowned Eagles, no matter their age or upbringing.
I had one female, Girl, a wild taken adult who would fly at a 45 degree angle from the fist directly over running Kirk’s Dik Dik, then plummet vertically down on them from as high as 10 to 20 metres. Her last second vertical approach was extremely fast and manoeuvrable, capable of spinning her around a bush. It had an almost 100% success rate whereas her captive bred offspring would simply tail chase and usually miss the same prey.
Recognising that any falconry-type hunt is poor evidence of methods used or prey species taken in the wild by wild eagles I shan’t document the methods used by the developing young, other than to say that hunting is learned, and they adopt some particular patterns as they mature. Young Crowned Eagles are particular poorly developed when it comes to recognising prey, and dissecting it. If captive bred birds are familiar at the nest only with a certain selection of whole prey they happily consume and dissect it when latter presented with them away from parental supervision. But if suddenly given a new species, such as a dead genet or Syke’s Monkey , they stare at it with confusion or even fear. Clearly parental choice delivered to the nest will be handed down to their young. Young eagles making their first few kills in captivity are inept to a degree seldom seen in other eagles. They bungle attempts, give up quickly, fail to anticipate avoiding action and often show fear. In killing they show a quick ability to learn which end is best to squeeze. Very soon, after a series of catastrophic mistakes and severe beatings they can subdue large prey by a head and shoulder grip. But once they have killed something they are keen to experiment and can be fool hardy. I suspect that they largest kills are taken by juveniles. This is the case with most raptors.

Mute, © Simonn Thomsett

I had better opportunity to witness these developing methods while hacking captive bred Crowned Eagles in Tsavo West, Mathew’s Range and Ol Donyo Laro over a ten year period. Nine chicks were born, hatched and raised with their parents Rosy and Girl at my home in Athi. They were usually removed at 4 months of age and then settled outside with a foster parent or older sibling to whom they sometimes associated and solicited food. Crowned Eagles are very easy to train but were never allowed to be tame and confiding of strangers as would most falconry birds. They were always managed to keep a reserve against people lest they not fear humans when wild. These trained eagles knew how to hunt at home taking hares, spring hares, mongoose, genets, Vervet Monkeys and much less often Thomson’s Gazelles and Black backed Jackal. The largest kills have been adult female Bush Buck and Impala, as well as their calves. They tail chased them then flattened them and a very basic and thuggish manner. The trained eagles were taken as ‘pairs’ for release and they profited enormously from being together. ‘Pair’ release is a method I would recommend for any re-introduction programme of large and socially complex raptors. They would hunt together, working a tree or bush until prey was flushed into the other’s path. This would often be by accident not design to start with then develop into a segregated task. After years of being together in the wild they would develop a working sympathy with each other that I was able to watch and not interfere. Usually the male would be ‘told’ to go in by the squeaking female. The female would sit high, look keenly at the prey beneath her and squeak and whine in a fever of over-dramatised intent. The male would appear to be driven to make the first courageous move, sometimes wriggling his way on foot in through dense thicket towards the hiding prey. She would reserve her pursuit and strike for the flushed animal, but as often make a mess of it by prematurely launching at the prey when she thought the male was within grasp.
Often one would land on top of a tree full of vervet monkeys. As they piled out of the tree the other (male usually) would take one on the way down or on the ground when running directly away. The level of co-operative hunting was unquestionably altruistic in that one would accept that it could not capture the prey, but serve only to flush it. Smaller prey was reserved for the male (such as female or juvenile vervet), larger (adult male Vervets) for the female. At all times the male would immediately relinquish prey he had caught to the female, even before it was dead although sometimes both would foot the prey especially if it was large enough to allow space.
None of these methods are unique for raptors. What emerged that only recently dawned on me as a probable ‘new’ hunting method worth publishing is as follows. What I witnessed was the quick and vicious attack on prey that appeared only to bowl it over and wound it. I had long ago been impressed by the ability of this eagle to seriously wound prey and leave it alone to die. In 1978 Rosy killed a Bushbuck female in circumstances I then did not think was normal. He hit the running female (only when it disappeared behind trees) that ended up upside down in a hedge. He hit it and was swung off it almost instantaneously. While deliberating what to do about the unfortunate Bushbuck, and worried about the fierce glare of Rosy in the tree above, it collapsed. I pulled it out while moribund to have Rosy violently push me aside and set about stabbing it along its entire length of neck. He then leapt back when it stretched to die. On PM I noted a huge subcutaneous bag of aerated blood, punctured rib cage and lungs as well as large haematomas on the neck. It had died of blood loss.
At a hack site at Finch Hattons Tsavo West a ½ grown bushbuck, always in close attendance with its mother, greatly excited one female eagle who followed it for 2 days. She made exploratory runs over it, to be thwarted by the mother turning to face her approach. On one occasion the eagle landed near the calf and the mother ran in and violently knocked the eagle away. The calf was inseparable, never leaving its mother’s side because of this attention. The bushbuck would associate more closely with Yellow Baboons, primates that these eagles had learnt to avoid. But wherever the Bushbucks went the female eagle followed. Suddenly the eagle tried a different approach and flew straight at the calf and knocked it over and continued on. The mother Bushbuck and attending baboons had no time to react as it was over in a flash. The eagle made no attempt to halt but flew and landed to watch the result. The calf, immediately got up and stayed by its mother with it ears hanging low. I found blood on the ground, and clearly the calf was badly wounded. The eagle then followed the calf relentlessly for two more days, showing evident curiosity (by raising its crown, craning its neck, standing on two feet, leaning forward and flying to different trees to keep them in view) every-time it lagged or stumbled. Finally the calf was unable to keep up with its mother and the eagle killed it. I did not see the kill, but arrived very soon afterwards to ascertain that the first impact had left a lethal wound that had gone septic and punctured the peritoneum making a large aerated subcutaneous lesion. I am sure the calf was unable to keep up and its mother had walked away and was unavailable to help. I saw a vervet monkey struck and left, in similar manner. It sat in a tree for hours, unable to keep up with its troop before it swayed and looked very sick. It was taken at near death when it offered no resistance about two hours after being attacked. The reason for so a long hind talon (measured at 10cm in one female and 9cm in two captives) is perhaps now evident. It is, as I liked to tell visitors to my eagles (making a few friends no doubt sigh with despair at its repetition here) “The largest killing implement on the African continent”!!! The needle tip, extraordinary length and incredulous strength of grip will, in an instant, puncture vital organs of any animal weighing under 50kg. To stab and move on would seem the stuff of undercover espionage agents armed with umbrellas, but it has the same effect. The two groves down the edges of the talon may harbour sepsis-causing bacteria if the caked blood and tissue clinging there is an indication. Like a Komodo Dragon the Crowned Eagle may have developed a “bite and retreat’ method of hunting. Even if sepsis is not the result, the effect of a deep stiletto dagger wound, followed by days of patient waiting is a very effective hunting method. It is a reptilian method not necessarily showing great intelligence that I believe is used by Crowned Eagles.
The vital organs lie close to the surface and surprisingly the heart is vulnerable to a relatively small puncture wound across a board range of body weights. For example, a mouse may have its heart 3-4mm under the skin. A rabbit, some 10 to 20 times heavier has a heart 10mm under the surface and an Impala some 25mm. A raptor with a 2.5cm hallux such as a Long Crested eagle, kills neither impala nor hares, but mice. So why the over-endowment? Perhaps it is because although the talons are long enough the eagle has too weak a grasp to puncture an impala’s chest. But a Crowned Eagle can extremely easily puncture an impala’s chest and break every rib within its span of foot simply by gripping it without the assistance of a fast contact speed.
The Crowned Eagle is an incredibly powerful eagle habitually killing as far I understand the largest prey of all eagles.

Crowned Eagle, © Simon Thomsett

Conservation of Crowned Eagles
Markus asks what should we do to conserve the Crowned Eagle. All matters of habitat change, water loss, declining food productivity is directly related to human population. While TIME magazine can attempt to dismiss the reality by saying we could all stand on Manhattan Island, if we all breathed in 500,000,000 would all fall into the ocean. There seems a reticence today to avoid broaching the subject of human over-population, whereas in the 1970s this was not so. I drove recently Kampala (Uganda) from Nairobi (Kenya) and saw (apart from kites) half a dozen raptors, 2 dead zorillas, and one live Reedbuck standing in an irrigated plantation. Apart from two small forests (each about 2km in extent) in Kenya, and 2 small forests (One 4.5km and anther 3km) in Uganda I saw nothing other than dense human populations, towns, shambas, Sugar Cane, towns, exotic plantations, towns, cereal crops, etc. The trip back covered some 1200km. Potentially the Rift Valley and lake basin, with super-fertile soils, varied topography and altitude, straddling the equator, should hold one of the greatest abundance of life found on the planet. And so it does, but it is mostly human. It unquestionably lies within the optimal core of former Crowned Eagle distribution in the sub-region. I doubt such a bio-impoverished or human dominated landscapes is what westerners expect to hear of a region as large as the British Isles lying in the heart of Africa. But similar rules apply elsewhere. Combine tremendous land fertility (such as the Ganges flood plain) with subsistence farmers and you tend to get biomass converted into people. It happens in India, Far East, Burma, Malaysia and sub-tropical Indo China, Latin America as well as Africa. Only high education and a new ethical world order on principled restraint to limit our full human population potential can intervene. But there is no indication that it will and there is certainly very few leaders who today would dare champion these matters.
In the Ethiopian bio-geographical zone, loss of net primary production between 1980 and 2000 is about 18%. “Moderate” desertification in Kenya stands at 64% and “severe” at 21% (1997) These percentages are expected to increase each decade and has already forced people from former high productive areas to drier marginal regions. Our urban and rural population is predicted to meet around 2050 with a total population in excess of 80 million. Unlike global predictions of a population plateau, ours still climbs off the chart at 45% angle, with no predicted stabilisation point. Wildlife is expected to parallel these changes with proportional declines. Education cannot be expected to catch up with the task and apparently nor can catastrophic examples of the folly of such action force change.
The accumulated effect of anthropomorphic factors appear to seal the fate of Crowned Eagles in our region; but is this applicable throughout Central and Western Africa? Most nations show similar trends and to expect different is to hope for a change in humans.

Given that people have repeatedly demonstrated their ability to exceed the holding capacity of the land to sustain them (as noted by Leslie Brown in the late 1970s), and given the lack of responsible leaders willing to address politically sensitive issues related to population control, it would be foolish to expect a long term future for Crowned Eagles. For the last few decades there is no question that protected areas have secured the Crowned Eagles and they continue to do so as long as they are allowed to remain.
If asked where financial resources should be spent in order to conserve Crowned Eagles I would roll out the standard (tailored for foundation) response. Namely stick to the buzz words of the day, “Create local capacity……… using Crowned Eagles as indicator species………securing environmental services through the conservation of water catchment areas………..working with marginalised communities to achieve………..Community based conservation projects………blah, blah, blah. Put one beer in me and I’d say what the heck, it’s all a waste of money because of the juggernaut of humanity. If you think that is bad, then put a lot of beers into my colleagues after the stand up show (conference) in which they enthused optimism and be prepared to gulp down much Prozac©, lest you feel a tad worried about the survival of your own children! There is a peculiar discrepancy between the personal thoughts of a conservationist, and their professional stance. There has to be otherwise they would be out of business. The business obliges optimistic outlooks and when none are obvious they may be invented. If only for a little while till humanity has a complete change of world order. Many projects must go ahead without a truly achievable end objective and this leads to an uncomfortable duplicity in the organisation/individuals concerned. Entering a project bereft of confidence is the sad lot of most conservationists in out part of the world.

Finally Markus asks “what was your most amazing experience with the Crowned Eagle?”

Once when I was a lad I was crawling on all fours through a forest path on the Amboni river near the Aberdares looking for what I hoped were Golden Cat tracks. All of a sudden the Robin Chats, Bul Buls, cicadas and all the animals went quite. The hush then turned to an avenue of alarm, from hornbill to monkey, from monkey to bird; and this onward rush of terror fled toward me! Stuck in a well trodden low tunnel I stared ahead down 100m of clear sun dappled view and was filled with primeval alarm. I knew a fast approaching predator was on its way and it was coming straight for me at a frightening pace. There ahead I saw her, golden eyes and silent, approaching at leopard height at unfathomable speed as steady as an approaching jet fighter. I distinctly recalled the fact that her wings were half closed and unmoving. I saw too the pattern of light and shadows flashing across her unblinking eyes. I stared enchanted, as must a man in front of a charging tiger, aware of the futility of action and mesmerised by the beauty of my attacker. I closed my eyes for the impact, heard a loud bang over my head, heard a sudden explosion of growling colobus monkeys and felt a light fall of twigs and leaves as well as the thump of air. She had punched her way through the brush above me. In that fleeting second before impact I noted a frown of disgust. I was not what she had hoped. If I had been I would have been dead.
I guess I had experienced a very rare thing. I was targeted as prey and she had launched her attack from a hidden and distant position. She had known all the paths, had heard my progress, perhaps seen other birds and animals note my presence. Undetected she had started an attack and had entered the tunnel at so fast a rate that she had no need to open her wings. She must have done that same path many times before.
I have been hurt badly by wild and captive Crowned Eagles, seen them kill enormous things, had them die after weeks of care in my arms, seen them hatch out of eggs and lived with them longer than any other relationship, human or animal. But that one simple thing is the most memorable.

Male Crowned Eagle, © Simon Thomsett

Replacement rate and longevity

If persecution was a factor then the breeding biology of the Crowned Eagle would predispose it, above all other raptors in Africa, to a gloomy future. While annual and biannual breeding has been recorded and its ecological perspective pondered, annual breeding is rare and probably related to the success, or not, of the previous season. Usually and possibly throughout its range it fledges about one chick every two years. The chick takes an inordinate time to reach independence and that alone is good enough reason for their slow reproduction. For a not-so-very large eagle it is hard to explain its slow fledgling and maturation period. I have seen begging 9-11 month old chick on the nest of an incubating pair, and also saw that same pair feed a 2-3 year old juvenile, possibly unrelated near their nest. That may suggest that recycling can be started before the chick fully disperses. I used to breed them in captivity and “pull” their chick at aged 4 months, to make them recycle for the next year. When they had egg losses (due to cobra and Honey Badger) they could lay again within weeks. It is interesting to note that on occasion Girl would lay two eggs. On one occasion when both hatched I saw no active Cain and Abel aggression other than the elder chick tweaking the toes of the younger. I did separate them lest one die of starvation.
The phenology of large raptors on the equator, especially those with stable prey base can hardly be expected to be precise. I’ve been uncomfortable with the dogma that there should be a season…simply because it is so in temperate places, but I must admit that come July, Aug, Sept my old pair would like to lay….sometimes irrespective of weather. Why I cannot fathom. But should I bump them into breeding in the first half of the year they would oblige (by giving them a stream of highly nutritious food (monkeys, springhares, small gazelles, etc)). In Kenya wild laying dates would seem to favour the latter 6 months of the year.
Female chicks take longer to fledge by about a week to a month and they take much longer to learn how to fly properly and hunt than males. While there may be a size overlap between male and female young (as well as adults) males are snappy, make their first flight and first kill quicker, certainly so in captivity. But in the wild I have also seen it so and presume that should a pair have a male, they may breed sooner the next year, than if they had a female chick.
The first year plumage is surprisingly varied. The most usual is the pure white fronted face, bib, chest and flanks and undertail as well as legs, often with a pinkish red wash on the upper chest. Slightly less common are those which one could easily have aged as two to three year olds. These just-fledged chicks, have darker patched faces, freckled bibs and slightly barred chests and spotted legs. While the pale ‘morph’ young just prior to leaving the nest usually have unmarked tarsus, they soon get spots on the front part of the tibio tarsal joint. I had at one time thought that there was a difference in the first year morphs between East and West Africa, but both Susanna Shultz and Guy Rondeau noted similar polymorphic first year birds in the west. By 4 months post-fledgling the inner thighs, previously poorly covered with downy type feathers, are covered with small feathers. The tibio tarsal pad is still bare and obvious up until it is a year old, whereupon it vanishes only to return to incubating females. Eye colour is variable too with some having khaki light brown just prior to fledging and others with adult-like yellow ochre eyes.
The plumage variations between sexes, as offered in some field guides is inconsistent and do not always apply. The various amounts of orange/rufous marbled patterning on the chest has been suggested as being sex linked. Some males have much orange on their chest and females have less, almost monochrome chests. But this does not always hold true. I suspect that most females have one less bar on the secondaries than do the males. While usually so it is not invariably the case. I have a suspicion that large females show female traits more strongly than smaller females; and small males show more male traits than larger males.
Plumage maturation therefore appears to depend upon sex, their size, and their particular first year morph, to say nothing of stress and variable nutrition. Of 9 young, 5 were male. Of these 2 males were larger and they matured slower than the 3 smaller males. It should be noted that in captivity moult can be accelerated or delayed by feeding regime and exercise. All these birds were trained, flown and hunted and therefore were most likely to follow a wild birds moult pattern. The females were less variable but all began their first flight feather moult a month or two later. They would half complete wing feather moult before the first deck feather fell. But not always. The first flight feathers were moulted out at 9 to 18 months, showing a marked lack of adherence to the calendar. Males are usually inseparable from adults at 4 to 5 years. Females (usually) taking half a year or more to mature. The only indication of juvenile feathers at this age are light crescents edging the distal part of each feather on the upper wing coverts near the carpals, obvious a year previously but at 4 to 6 years becoming very faint. Irregular moult can certainly be protracted due to stress, nutrition or work, and while it is usual for one moult will be overtaken by the next, some old ragged feathers may be retained. 3 and rarely 4 moults can be seen in an individual. Of particular interest is their ability to moult damaged feathers early. If any primary is fractured and left so (not imped), it will drop sometimes 10 months earlier than expected. My old male has a poorly healed humerus and fractures feathers on that side with frequency. He has replaced primaries in this wing many times more than on his good wing. At 32 years he developed a single white tipped greater upper wing covert, in mid wing, which increased in size at age 33. His mate a similar aged female also now sports a single white tipped feather on the same wing and same location. These maybe senile related.
Moult in Crowned Eagles is therefore a complex affair, but I suspect more temperate eagles would adhere to a calendar a little more fastidiously.

Behaviourally Crowned Eagles are nervous, constantly alert and on edge. Females are more phlegmatic but never docile. They are highly intelligent, cautious, independent and inquisitive, unlike African Hawk, Tawny or Verreaux’s Eagles. In their training and management they are more like goshawks than Aquila eagles. Being permanently curious and edgy would seem to be a common trait for most forest raptors. I understand that the Harpy and Philippine Eagles are much less nervous however. While I might be poo pooed for noting ‘intelligence’ I have no end of examples that place them in a unique position over all other African eagles, particularly when they hunt. They cannot be induced to hunt large prey by increasing their hunger, as would a Verreaux’s or Tawny Eagle. They may show moments of cowardice that while shameful, may expose a unique aspect of their hunting strategy. They are variable in temperament too as individuals to a degree greater than that found in most other raptors.
One thing is for sure, they are a highly variable species, in colour, size, maturation period, behaviour, prey preference, habitat use and requirements.

Crowned Eagle, © Simon Thomsett

Because of their low fecundity one would assume that Crowned Eagles were exceptionally long-lived. My male Crowned Eagle called Rosy was over a year when I got him in 1978. His mate Girl is about the same age. She is fine today and not a whit older, but Rosy had to undergo a bilateral cataract operation. Importantly it was not senile related and the eye surgeon was amazed to note that he had the immune response of a human child. They still have the will to breed, nest building and even mating. I would credit some wild Crowned Eagles in benign environments at easily reaching their mid thirties, and it cannot be impossible for some to reach 50 years or so, as can other large raptors. However when I visited Susanne Shultz in Tai Forest, Ivory Coast I was shocked at just how close those pairs were to each other, for there is one thing I know, battles between pairs are violent and life threatening, especially if you have those feet. I cannot imagine that those packed in, jowl to jowl, territories do not have murder as one of the main causes of death. Tai is a tough neighbourhood, whereas our nice clean community of more widely spaced eagles that we see on cosy wooded hill tops in Kenya, would be less likely to indulge in such behaviour. Mind you, given that our Kenyan territories are often fragmented patches, there may be deliberate take-over attempts for these isolated territories. Leslie Brown had birds that occupied one nest 9, to 13 years, but these do not discount territory moves which may well happen. I had one adult female who later died brought in with deep wounds that were certainly inflicted by another eagle. Another natural cause of death expected to be exceptionally high for this species is injuries incurred during struggles with heavy and well armed prey. In witnessing eagles killing vervet monkeys, a relatively small monkey, I have been impressed by the way some monkeys will fight back with their arms, hands and teeth. I once arrived just after a young female Crowned Eagle had attempted to kill a full grown female baboon and suffered the wrath of troop members. She would have been wounded or killed had I not intervened. I treated a wild female for an ocular inclusion in which debris had been injected into the eye and destroyed the lens. There was another lesion the same distance as the separation between Suni horns and I assumed that she had been head butted. Tom Butynski concluded that a monkey had harmed a chick in the nest that later died in S W Uganda. I have lost two released eagles, one to a leopard that surprised a male on a monkey kill in the rain, and the other from a crocodile that took a female as she ate a young bushbuck kill near the water’s edge. Other causes of natural death are probably starvation and disease. But trauma related deaths would seem to be high for this species.
Of deliberate human persecution I have personal recorded them being shot by an expat with Burmese cats in Karen, shot by a big cat conservationist for eating geese in Karen, shot by sheep farmers in Mweiga and Timau, shot by KWS rangers in Elgeyo Marakwet and Rombo, shot with arrows in Cheranganis, poisoned in Kibwezi and Maua Hills (Machakos) and Cheranganis, caught in snares in Cheranganis and finally nest trees deliberately cut down in Cheranganis and Mweiga. Another male was beaten to death in a corn house whilst killing a dog in Elgeyo Marakwet. Of accidental deaths I saw a juvenile female with and amputated wing severed by a snare set for ground game in Karen forest. One male at Ololua attempting to take domestic geese in a chicken wire pen in Leslie Brown’s old house was snagged but fortunately rescued.

Export and trapping

Markus asks if the bird trade is any threat. The amounts reaching their destination under permit may be sustainable, but those caught to supply them is a different thing. Given the amounts exported I would doubt if it would be a global threat, but I do consider their brutal trapping and subsequent terrible husbandry and resultant mortality a threat to local populations. The trade is of course an effrontery to conservation.
I recall two Crowned Eagles being exported from Kenya, one in the 1960’s by Cunningham van Someren, and another in the 70’s by Don Hunt. Both went to zoos. I suspect a few more were exported, but not many, chiefly because of the difficulty in handling them. From my experience in rehabbing raptors, I have been appalled at the handling and husbandry methods made by the public and trained government officials as well as most vets. I once saw a tethered Martial Eagle, meant for export in the 70’s with both legs tied with a piece of rubber inner tube, wrapped around an open fire in a hut. The children were busy taunting it with a stick. The trapper was a professional and I was unable to confiscate the bird. It must have died for it never reached the export company run by an internationally famous conservationist. I have seen many birds and raptors in capture holding pens, some feeding on each other, in conditions where mortality or irreparable damage is virtually guaranteed. From what I can glean from the highly secret businesses in Tanzania and Uganda, similar treatment is the rule. I once estimated, based on the trappers, and the company owner’s own admission, that some one in ten captured raptors would survive to get put on the plane.
I dread to think what lengths of brutality a trapper would go in restraining a Crowned Eagle, an animal that could maim or kill a human if given half a chance. I cannot imagine what sort of trap they would use, or how they would house it. But you can be assured that the process is cruel and life threatening. I would expect a higher mortality rate for Crowned Eagles than most raptors, simply because they are very awkward birds to handle and are easily stressed and likely to self mutilate against cage walls.
If for every one bird exported one must capture 10 birds, and each bird is an adult, the impact is considerable. This is an open question as no-one knows the details, nor is one allowed to know even when asked by officials to make an opinion.
The significance of the removal of adults, juveniles or chicks is not considered in the various regulations. Despite very good reasons to separate these age groups when it comes to a harvest quota, it is not done. Falconers of old never took haggards, or only rarely when they knew they were not breeding. They took passagers or eyasses. These juvenile birds experience such high mortality that it makes little difference to the population as a whole if some are removed. Established breeding adults are crucial to the survival of the species and represent a small fraction of the yearly crop of young and as such should be left alone. With this ancient wisdom, why is it that modern biologists have yet to enforce the same protocol in the raptor export business and within the CITES regulations? The absence of deferential treatment or harvest rates for age groups illustrates an oversight.
The removal of unfledged chicks or eyasses from the nest, if done smoothly and unseen can be least disturbing. This applies to nests with multiple young from which the adults are allowed to raise one or more chicks undisturbed after some have been removed. But Crowned Eagles raise one chick every two years, and their investment in that one chick and nest site is monumental compared to almost all other birds of prey. The removal of a single eyass out of a Crowned Eagle nest represents a total failure of not one but up to two years investment. It is a catastrophe to the adults, and may well make them move site.
If a delicate Cain and Abel rescue is made then one takes a chick that would otherwise die when it is aged only a few days. It demands well orchestrated teamwork with months of close watch, hides, an intrepid climber or two, incubator/brooder, 24 hour care, precise diet and foster parenting. Crowned Eagles in our latitude rarely have 2 eggs, and siblicide is therefore an unusual occurrence. I believe chicks have been taken by this method in Zimbabwe and South Africa, but I would doubt it being the method adopted in Tanzania or Uganda. There is of course the absolute certainty of human imprinting the day old chick so removed, unless one happens to have a captive pair of foster Crowned Eagles under which it can be raised.
A human imprint Crowned Eagle is never likely to breed (except by Artificial Insemination) and be a danger to people and is a lost member to its own species. There really cannot be much justification for having such an eagle.
I have never understood the need for exotic raptors in zoo, aviculture or falconry collections and think it unethical. I believe that the main rationale is not conservation but either egotistical or financial. The bigger and more complete the collection, the more kudos or visitors. I have argued aggressively against exotic species being used in falconry to the bewilderment of many, who think only in terms of sustainability.
I do see merit only in real conservation arguments that outweigh the loss of the birds from their home country. These could be life saving for the individual bird, treatment, captive breeding for re-introduction, or saving a species in captivity when its wild habitat is defunct. If there comes a time when captive breeding for re-introduction is deemed an option Africa certainly has the proven capability of doing it themselves. However permission is seldom if ever granted for domestic use, but readily granted for export.

Importers could and do argue that they need the birds for captive breeding, as if captive breeding is a panacea of its own. But I know of not one single incidence of an exotic raptor benefitting from this exercise. (Except for bonafide work by established conservation groups for E.G. for the Mauritius Kestrel). Should the breeder have a plan to export the progeny produced to augment our impoverished populations then that could be considered as an option. But no, the export of raptors from Africa is a one way ticket to oblivion from which nothing returns.

Tanzania is one of the few countries with a well established wildlife export trade and large eagles as well as the Crowned Eagle appear not infrequently as subjects for export. In theory, a legal harvest is dependent on a scientifically substantiated population estimate from which one can calculate a ‘take-off’ quota. No-body knows the sustainable harvest quota for Crowned Eagles and no-one knows the numbers in Tanzania, so it should be inappropriate to entertain export, but it happens in spite of pleas to reconsider. From its slow reproductive recruitment and slow maturation one would immediately impose a precautionary approach to their harvest, but this is not understood showing an absence of consideration for their unique biology.
Neil Baker’s invaluable compilation of data for the Tanzanian Bird Atlas has numerous advantages over Kenya in being contemporary and reliant on a larger informant network. From his work it appears that the Crowned Eagle is patchily distributed and nationally sufficiently rare to support a no export policy. The pattern of occurrence, density, threats and problems are not dissimilar to Kenya, but if one would include ‘export’ as a threat it has one more additional problem to contend with.
It is ironic that I have spent much time and money breeding and releasing captive bred Crowned Eagles on the border with Tanzania, to have the Tanzanians legally capture and export the very same species. It is poignant to note that I had painful bureaucratic hurdles to leap and still suffer from critics who disapproved of the release programme yet CITES and IUCN make it much easier to ship them out to zoos for profit. On one side of a border we consider such augmentation a worthy exercise, requiring at one time the full back up of KWS, volunteers, Finch Hattons Lodge, a project vehicle, a home -made aircraft, radio telemetry and running expenses. To have on the other side of the border a few kilometres away, someone ship them out to die overseas.
When we are asked on the raptor network to make a comment regarding a raptor species destined for export, we are obliged to remain unemotive and respectful of the country’s policies. Casting sentiments aside it is still extremely difficult to understand why one should export (or import) Crowned Eagles. Africa certainly exports raptors on license and with CITES permission, but there is no evidence to say that this exercise in any way benefits the wild resource. There is every indication to say that it harms it and every ethical perspective to say that it is wrong. Money is the only objective as there is no local conservation related obligation demonstrated by the receiver. I question the ethics of the importing country and individuals behind capturing Crowned Eagles for raptor exhibits in Europe, USA or Thailand (see Youtube for the latter!). There are a number of falconry trained Crowned Eagles in Britain and one even in Scotland, where Golden Eagles would be much better suited. If Crowned Eagles were common and stable, I still see no ethical reason why they should be harvested and exported. If the importer makes any claim that they are supporting conservation they have yet to demonstrate it. If some argue that they have secured the species future, albeit outside their doomed range, they have yet to propose any action to support a programme to achieve this objective.

Juvenile Crowned Eagle, © Simon Thomsett

Future predictions for forest species

Recently I listened to Don Turner giving a talk on the status of birds in Kenya. He is a world renowned ornithologist and author with a precise analytical mind and spans pre and post colonial Kenya. He talked of the big picture, of global warming and of Kenya’s invigorated complacency and emerging lack of accountability for what we too happily assume to be only a western evil. Namely, Global Warming. (Africa burns the size of Australia each year, without guilt for carbon emissions, for EG.). Don spoke of Kenya, its 5.5 million inhabitants in 1955, and its over 41 million (published) today, showing little sign of abating and doubling in less than 15 years or so. That’s 20 million below 15 years old. (Even government admit to 71 million by 2030.NB. 4-6 times growth by 2100). UNEP had once calculated a maximum holding capacity for Kenya at 22 million, and we’ve doubled it already. It takes less than 3 years for us to add the same population it took humanity more than 3 million years to achieve by 1955. He then listed those bird species that have gone extinct, those that have not been recorded for many years and those we know will go extinct. Not surprisingly these were mostly forest birds. (NB. The only raptor to be officially extinct in Kenya is the other forest eagle; the Cassin’s Hawk Eagle). His frustration was evident and when questions came the unanimous consensus was that Kenyan conservation organisations and all the associated NGOs had failed shamefully at even raising the matter of “OVER POPULATION” and “UNSUSTAINABLE” land use practises and the devastating effect it has on our bio-diversity (ESPECIALLY FORESTS). All agreed the systems in place to evaluate threatened animals were disgracefully deficient. I thought his lecture refreshing because it did not sugar-coat the facts and moreover, was totally accepted by an entirely Kenyan audience. This audience had no ‘politically correct’ agenda and no hang-ups about putting the blame where it is due. I have to add than even in my most pessimistic mood the outlook was much worse than I had assumed. While a critic, I had also been subconsciously deluded by the current status evaluations persistently voiced by large NGOs. Perhaps I too have been successfully duped by KWS branding propaganda and national zeal that sells Kenya as a success. We all felt deceived and let down. The implications were clearly that we were facing a catastrophic unparalleled loss of forest species and bio-diversity and that there were no functioning actions in place that would mitigate these losses. This conclusion was applicable to all countries in Africa with similar human demographics and policies. It was probably worse in those countries considered unstable.

Two kinds of Crowned Eagles

Many authors have recognised the distinct difference in prey selection between Crowned Eagles living in forests and savannah biomes. Leslie Brown in Kenya, as well as observers in South Africa (Boshoff, A.F., Palmer, N.G., Vernon, C.J., Avery, G., Jarvis, M.J.F., Symes. C.T., Raath. A.) all noted a shift away from monkeys when living in “bush” environments and a shift in hyrax and antelope species. However these forests hardly compare to those of the central and west African types, and differ so markedly in species abundance and prey species ecology, height, quality and extent as to be incomparable.
These populations under study often occurred adjacently or within a small area sufficient for none to assume any real difference in the birds, only their prey. While I suspect that there are physiological and behavioural differences that define these two groups at the extremes of their occurrence it helps in estimating their status if they are so separated. Crowned Eagles are ‘true’ forest eagles apparently (thanks to recent DNA work) more closely related to old world Hawk Eagles than to any other. But the Crowned Eagle has been isolated from its closest relations long enough to have evolved independently and be unique in being that much larger and more powerful. (It is one reason why ‘hawk’ in Crowned Hawk Eagle has been dropped). It has the classic accipitrine body build with short wings, long tail configuration, the harpy-like facial ruff and crest, the deep brutish eyebrows (protection against violent collisions against brush), and a nervous disposition so similar to accipiters. These all support its forest roots. Perhaps monkey predation did originally drive its evolution by increasing its size and foot structure. The tarsus has tall ridges that run its length separating massive tendons and increasing the strength of the bone. The twist, said to offer a dynamic shock absorbing rotation is hard to understand, but certainly sets them apart in an area where raptors need it the most. All in all it is a surprisingly well designed eagle despite its somewhat primitive Neanderthal looks.
Despite having a typical forest adapted ‘flight envelope’ it does not oblige them to a life confined within closed canopy, but significantly they do use it to the exclusion of other large eagles and they almost certainly evolved within it. The other large eagles cannot penetrate their forest realm, but when the Crowned Eagle exits the forests they share their foraging ranges. Their evolutionary home would appear to be dense tall forests, and from that it has cautiously ventured out to less dense more open habitats. These eagles can be split into ‘Forest’ and ‘Bush’ eagles. While an artificial partitioning it is deserved, and needed for their evaluation.

The ‘forest’ eagle.

The supermarket of food in the African primary forests is mostly monkeys. A staggering 350 to 558 individual monkeys per square km is possible in these tropical forests providing an easy to see, if difficult to kill, food source. Killing monkeys needs two things, suitable weapons and strategy.
Of avian competitors in forests it has none. The Cassin’s Hawk Eagle is to all intense and purpose a thick-set Ayres’s Hawk Eagle or forest adapted African Hawk Eagle, certainly not a true Spizaetus Hawk Eagle or smaller direct relation to the Crowned Eagle. Its prey range barely overlaps (large squirrels) and it is not a serious competitor for food and an inconsequential problem with regard to nest sites. Monkeys are tough and have long limbs with powerful hands that grip and huge canines to bite. Very few eagles, even the (previously termed) Philippine “Monkey Eating” Eagle, or the Harpy Eagle prefer monkeys. While ‘bush’ eagles have much less monkeys on their menu, ‘forest’ eagle life revolves around them. The ‘forest’ eagle is numerically the most abundant and probably the most important medium sized carnivore in these forests, devouring the most amount of meat. Given their combined numbers, prey range and physical daily nutritional needs they consume more than any single predator such as the Leopard or Golden Cat. These forests are typically devoid of canid hunters/scavengers, hyenas, or terrestrial predators. The way things work in these forests is different from what we in savannah Africa are familiar. Here in the forest the Crowned Eagle is King, whereas the ‘bush’ eagle is not.

A titivating recent hypothesis is that a distant ancestor of the forest dwelling Crowned Eagle moulded and shaped the early monkeys. The “taphonomic” implications of Crowned Eagle predation on hominid evolution makes for compulsive reading. I have little idea what “taphomology” is all about but have no doubt it adds some credibility to whether Crowned Eagles moulded slow, small, daft arboreal proto monkeys into US? Alarms voiced by those early monkeys at seeing their main predator became complex and led to communication, group cohesion and delegated roles in their community. Even their physical agility and vision could, in part, be related to those pressures placed upon its evolution by an avian predator. An active arboreal life for an animal weighing over a couple of kilos is a diurnal one, for leaping into space on distal tips of branches in darkness would lead to an early demise, as gravity, darkness and weight are a bad combination. A larger body mass would therefore make you diurnal and vulnerable. You have to be smart and small but then a much larger body mass would make you less vulnerable as well. Predation by the ancient Crowned Eagle was most likely the pressing factor that increased primate body size as a way to beat predation. It came at the great cost of loosing access to the most nutritious distal leafy parts of trees. Some of the heavier monkeys descending to the barren, least productive forest floor and this obliged them to eat invertebrates and meat and predate. This created an omnivore with a smaller gut that also allowed quick bipedal movement, more time on its hands and the essential nutritional building blocks for a larger brain. Perhaps then as is true now, terrestrial predators in forests were few, but they would still retain an ability to climb trees as we do today. Perhaps the early proto Crowned Eagle could see the writing on the wall for it seems that one did its best in squeezing the life out of the Taung australopithecine child. That the Crowned Eagle is the only confirmed ‘juvenile man eating’ eagle today makes it highly likely that it was at one time a real threat to smaller early hominids juveniles. Sadly for the eagle, it may have contributed in transforming a tree dwelling small primate into us. Predation is a persuasive reason to evolve, and when one thinks about it no other predator could have been as important to early medium sized primates. I’d like to see one of those artist representations of early man evolution with each figure looking skyward waving a stick and hollering “watch out” in lesser and lesser degrees of intensity.
If this theory had any merit then why is it that the Harpy Eagle didn’t round up those backward new world monkeys and make those into terrestrial giants with brains? The Harpy’s main food is sloths so why in heck didn’t those evolve into huge beasts that had to descend to the forest floor. Oh, hang on, maybe they did, and we bumped them off.
Sometimes after having seen a truly monumental kill made by this medium sized eagle I shudder at just how life threatening they would be if they weighed only 2 to 3kg more. A Crowned Eagle weighing 12 to 18 lbs would be well within the weight range and flight envelope of a Harpy or Steller’s Sea Eagle. But it would be terrifyingly capable of killing humans. If it weighed say 25 to 30lb (such as the Haast’s Eagle of New Zealand), it would probably specialise in humans. I suspect many such ‘hazardous to human life large eagles’ were killed off by man, and you have to wonder if somewhere in the sub fossil strata of Africa’s rain forests such an eagle remains to be found.

I learned an enormous amount about the ‘true’ ‘forest’ eagles from Dr Susanne Shultz when I was asked to go to Tai Forest in Cote d’Ivoire for the Peregrine Fund to catch some of her study birds. I learned much too from simply looking around me in an environment, though tangibly similar, wholly alien. I found those ‘forest’ eagles as different and incomprehensible as a foreigner. They just were not the same as the ones in East Africa. One species can behave differently depending upon its environment and the distance between them. I was able to handle these eagles and compare them to the Kenyan variety and I did note subtle differences. And why not, for these eagles have been as separated from each other as have the Forest from the Savannah Elephants. I found them smaller but as large footed, thuggish in build with deeper eyebrows, noisy and pugnacious in character. I’d like to call them S. c. troglodytes ! Sadly these subtleties in structure are hardly quantifiable and unlikely to galvanise the ornithological taxonomists into desk-pounding proclamations of agreement.
One important thought occurred to me as I walked out across a broad lateral branch high above a green carpet of lower canopy trees in Tai, was the three dimensional extent of these forests, compared to those used by ‘bush’ eagles. One doesn’t have to sit through the agonisingly predicable “Avatar” movie to get a hang of what I am trying to describe, but it would help. It would help too if you saw it with 3D glasses, and not a pirated version on your laptop. The ‘forest’ eagle group lives in high, multi-layered canopy wet forests. The usable foraging area must consider these forests in terms of total surface area in the vertical aspect.
These horizontal multi-storied canopies and tangles of vertical growth harbour a whole world of epiphyte fauna from large to tiny sun and flying squirrels, tree mice, Pottos, galagos, Palm Civets, hyrax, a multitude of birds, tree pangolins, dormice, lizards, reptiles, hornbills and an unequalled array of monkeys. Literally tons of animals live in the trees and seldom descend. From the top canopy you look down upon the feeding animals, themselves high up on the tops of trees. On the ground surface dwell the mixed groups of Duikers, Suni, Bushbuck, Chevrotains, Liberian Mongoose, Cusimanse, Monitors, Dwarf Crocodiles, Bush pigs, Forest Guineafowl, Congo Peacock and Mangabeys. One underappreciated habitat is the tree buttress bases, limb falls, vine tangled glades, leaf litter and the upheaval of root structures that has no resemblance to tera firma, but to mouldy cheddar cheese. The terrestrial and arboreal species move together like gigantic communes. Food, fruit, rejects, faeces and litter is dropped from above and consumed below. Just as small bird feeding parties move together so do these and in so doing they move in and out of territories of Crowned Eagle pairs. These eagles must hit these parties as they pass through the neighbourhood like kids chasing an Ice Cream van. In other words there is a time of plenty followed by paucity and there must be plenty of territory infringements and disputes. As a result Crowned Eagle behaviour must to cater for this.

Here the monkeys alone amount to a weight of meat biomass available to Crowned Eagles in access of the meat found in the migrant ungulate ecosystem of the Serengeti. Little wonder that Crowned Eagle densities can be very high at 1 pair per 6.5km2 given that prey density! That’s less than 1.5km between each nest….a veritable colony of breeding eagles! But their actual foraging range is multiplied by the surface area that the multi-tiered canopy and vertical surfaces provide. One cannot compare the number of potential victims a serial killer stalks in a 5 sq/km quadrant of sky-scrapers in Manhattan as opposed to a similar size in single storied suburbia. In other words the actual surface area available to a forest eagle may be at least 3 times the 6.5km2 (some 20km2). The amount of suitable prey available is open to conjecture, but it is much more than in any other environment.
While there is a staggering supply of prey it isn’t as one may assume (for tropical forests) a steady and guaranteed uninterrupted year-round food supply. One aspect of possibly crucial importance to Crowned Eagle biology is the need for most of their prey species to forage together and move to seasonal fruiting trees. They move in noisy close-knit groups as much for detecting food as for mutual protection from Crowned Eagles. Although eagle territories can be small in these super-productive forests they may be more fiercely defended. I’d doubt any relaxing of boundaries for intruding eagles bent on following these feeding groups within neighbouring territories is permitted. Feeding groups of prey species must wander outside of a pair’s foraging range and thus often leave pairs with little prey, while other pairs have over-abundance. When the monkeys and duikers have left an eagle’s “patch” they must either rely on reserves or be able to kill larger or smaller-than-usual prey species that are left behind. They must have strategies that keep them from going hungry. I believe that their hording or “caching” ability may be one very well developed habit not entirely perfected to the same degree by any other eagle. This caching may help them through the expected time of paucity as well as be a more efficient use of hard-gained and large food. The dissection and transport of limbs, nearly innate even in captive bred Crowned Eagles, is only practical for large prey. I am unsure if any other large eagle has this habit. It also hints at some intelligence and forethought. One macabre anecdote is that while investigating an alleged kill of a human infant (4 year old girl) I was brought to the tree where her severed limb was found. The circumstances led to no doubt that the accusation was true for no leopard could have climbed that tree, and nor did the locals know that eagles cached limbs.
One plausible survival strategy when things look bleak is to hunt prey outside the normal prey range. I once found a trained male Crowned Eagle, left out for the night on a freshly killed dove early the next morning, and I have also flown other males at spurfowl and guineafowl with some success. Small males in particular can hunt birds quite frequently, and I knew of a pair in Mweiga that frequently took Kenya Crested Guineafowl and Leslie Brown once found a fresh Marabou Stork! Apart from birds they can also kill very large prey.
The Crowned Eagle would seem to be overly well-endowed with massive killing feet. None can talk of this eagle without reference to its extraordinary power and ability that, if it so wished, can kill animals 10 times its own body weight. If in doubt, Youtube the less powerful Golden Eagles killing Wolves and you’ll get confirmation that eagles can kill very large animals if they have to. The desperate hungry young of most raptors (both wild and captive) are reckless and capable of extraordinary feats of strength. One must put to bed the oft-repeated notion that eagles cannot kill very large prey even though it does not do them any favour amongst sheep farmers! Acknowledging that they can, opens up an intriguing debate as to why they do, but do so rarely. On occasion a Crowned Eagle can step into the mega-carnivore niche and this should surely have a survival benefit for when usual prey is temporarily unavailable? Larger forest animals such as large duiker and bushbuck may have less need to eat nutritious fruiting foods and thus are more sedentary and stay within confined territories. These species can be found alone and not be dependent on sentinels. In high latitude parts of the world when food is suddenly made scarce due to hibernation, snow, inclement weather or migration, food deprivation can drive an eagle to kill much larger prey. The seldom used reserve of immense power has an easily understood survival benefit in these circumstances. It does have its dangers of course in their being injured or exhausted to collapse. But it is an important, intriguing and yet curiously neglected part of many raptors’ biology.

Crowned Eagle nest, © David Gulden

The status of ‘forest’ eagles can be made by quantifying the square kilometres of land under primary forest, and by subtracting most of those forests that have been poached out for bush meat. For an eagle it historically must have been surprisingly abundant, but few would argue that good quality forests with prey is anything other than a rarity and under severe threat. From a status point of view the ‘forest’ eagle occurs in those rapidly dwindling, formerly vast tropical rain forests of West and Central Africa. We can make fairly good guesses at their rate of loss if we know the rate of loss of these forests and their prey. Unbiased interpretation of satellite imagery should give one a good estimation.

The ‘Bush’ Eagle
‘Bush’ eagles are those that have ventured out of the wet jungles and colonised dry forests, moist central African-type isolated remnants, riparian and open highland woodlands from Ethiopia, southern Sudan, throughout Eastern Africa and down through the miombo belt to Southern Africa. In East Africa many forest patches were found clinging to the tops of isolated hills and mountains, and on inspection almost invariably had one pair of Crowned Eagles. These forests, respected by law and custom survived up until the late 1970’s when the human population seemed to tip the balance and lead to a country-wide loss of quality and extent of this eco-type. I believe it quite feasible to state that if a country has a certain human population density, some species can survive, but add on a few more million and they cannot. Those forest patches exceeded that threshold 30 years ago when we had less than half the human population.
Their day to day life, prey base, food security, hunting methods and competitors are different to the ‘forest’ eagle. I have watched soaring ‘bush’ eagles high above a thin riparian forest launch a successful attack against young warthogs feeding out in a dry desolate treeless plain. The flight, attack and location was atypical of the species, but it did not look out of place at all. These eagles hunt open area species small ‘plains game’ ungulates, carnivores, mustelids, viverids, primates, rock hyrax, hares (even Springhares) and so differ from the ‘forest’ eagles.
I was lucky to have sat with Leslie Brown looking out across the tiny forest patches of Ololua and Eagle Hill looking at his famous eagles and hear him speak of the changing menu of those pairs as forest prey species were lost and replaced by more open savanna species. Their adaptability within their own lifetime was impressive, with the Ololua pair changing its diet from diurnal Suni, duikers, monkeys and hyrax to nocturnal genets, mongoose, greater and lesser Galagos and hyrax in the 1980s. The change was forced upon them as poaching and disturbance obliterated the diurnal species. Notably they struggled to breed successfully for a decade before becoming only an occasional and non-breeding visitor. A change in diet such as this may be a pre-emptor to loss. These scrounging desperate eagles are picking the bottom of the barrel and Crowned Eagles that utilise unusual, domestic or nocturnal animals should not be thought of as successful.
These ‘bush’ eagles closest neighbours are not usually their own species, but other large eagles with some prey overlap. Aggressive encounters with their own are less likely but they must compete for space, food and sometimes nesting sites with other species such as Martial, Verreaux’s, Tawny and African Hawk Eagles and thus lose their monopoly. Having other species as immediate neighbours may help buffer encounters with other Crowned Eagle pairs who live the next street over.
The ‘bush’ Crowned Eagle’s distribution is not straight forward to predict. In Eagle Hill near Embu the famous Crowned Eagles lived in an area of some 10sq/km of forest patches interspersed with rocky out-crops and low thicket-clad hillsides. But other similar neighbouring hills, larger and as attractive did not have a pair. The wooded hillsides formerly so typical of mountains, rift escarpments and hills throughout Kenya were certainly likely to have pairs up until the mid 1970s, but it would be hard to estimate exactly how many without each being checked. Because each pair owned a forest patch and were separated from the next forest patch (10km to 40km) it was not possible to estimate density in terms of 1pair/??km2 in the same manner as those ‘forest eagles’ in contiguous forest. The Eagle Hill pair were alone throughout Leslie Brown’s 378sq/km study area during the 1970s for example, but that is not to say there is 1pr/378km2. The nearest pair I knew of was some 50km distant making the density 1pr/2500km2, or not. From a satellite photo these isolated and small locations would be tough to predict as Crowned Eagle habitat and one would be seriously led astray if one persisted in establishing a density figure for this habitat.
In contiguous forest Leslie Brown thought nests were separated in Kenya by 15km, and this may have held true in our highland forest where biomass is less abundant. I encountered 4 nests some 5 to 6km apart in the Aberdare’s Salient, but worried about being so bold as to make a density estimate. For one thing, each nest tended to be in a valley and pairs would utilise that valley in long winding corridors. In the adjacent valley, over the ridge another pair would operate 5 to 6km distant. While nests may have been close, actual territory use was linear or wedge shaped and separable by ridges. Short of radio telemetry work establishing territory size in East African fragmented forests is tough. Because of “edge effect” particularly where park boundaries meet densely populated rural farmland communities with small livestock, I suspect that nesting sites and territories require a buffer of at least 2km. But in more tolerant areas without high level of persecution they can nest within (see Ololua forest pair in ‘Urban Eagles’), some 100m of human habitation.

It could be supposed that a population that lives in drier less productive areas would have less biomass available and less density. Within these restraints ‘bush’ eagles, particularly at higher latitudes would be expected to reproduce less, mature slower, live longer and have heavier body weights. Perhaps they do.
The status of the ‘extralimital’ ‘bush’ eagle population is probably as important as the forest eagles, if not so dense, it is wide spread. However statistics on the presence or removal of suitable small forest and woodland habitat across this region is worse than that of the rain forests, as it is not seen as an eco-logical crisis worthy of investigation. Dry woodland loss is deemed less noteworthy of international concern, difficult to qualify and quantify on satellite imagery and frustratingly difficult to assert as suitable for Crowned Eagles. Leslie Brown used to wonder why it was that seemingly less suitable sites would have many eagles, yet others larger, and to us, better sites did not have nearly as much. It is therefore not very easy making accurate judgement of a forest from afar, and footwork is required.

The urban Eagle
No summary of the Crowned Eagle would be complete without reference to their ability to nest within very close proximity of sub-urban humanity. In Kenya the famous Ololua pair that nested within sight of Leslie Brown’s office window in Karen was testimony to their tenacity. That same site was known to the Bursell family back in the 1930s, and it survived regularly producing young until the late 1980s. It was one of the last pairs to go from a list of 23 known to me. Nesting activity ceased in 1994 and by 2005 Crowned Eagles were very rarely heard or observed in the area. An adjacent pair nested on a Cape Olive only 120m from the road I used to take to school. The site was within Nairobi National Park, but they must have used residential suburbia to hunt. Today that pair seems to have moved 500m to a small eucalyptus plantation, incongruously still within the park’s boundary but adjacent to a main road. Yet another adjacent pair nest in a croton in a newly formed sanctuary near a mortuary, racecourse and show ground. I recall incidences of direct persecution of these eagles, one shot by the secretary to the Elsa Trust, another shot for eating Burmese cats, another shot in Mwitu Estate for again eating cats. These individuals, despite an educated upbringing and very aware of conservation issues epitomise the NIMBY (Not In My Back Yard) sector, that is all too prevalent in Kenya.
In Durban such a pretty scene is repeated. Pairs nest in river gorges that have on either bank a suburban setting. Pairs nest elsewhere not in protected indigenous forest parks but in forests sometimes dominated by plantations of exotics.
These pairs have one thing in common seldom if ever encountered elsewhere. These territories lie within the affluent, well educated elite communities who raise Swarovski binoculars at them, not (usually) shotguns. It is absurd to assume that this pattern of occurrence is replicated anywhere else where no such veneration will excuse the eagles of their depredation of livestock or bush meat.
The forests near Nairobi have governance and protection seldom afforded any other forest (other than those protected in well managed national parks). There was for example dead timber on the forest floor, suni droppings, minimal livestock, minimal snaring and low human disturbance. Whereas other forests, far from the capital city, even in much less populous areas have as a rule a rural community to sustain with firewood, livestock grazing and other natural harvestable produce collection. Incidentally those pairs in suburban Nairobi forests are by no means secure and are probably under immense stress and should not be held as examples of the success of the species.
Previous to the aforementioned gum tree nesting pair I never knew or heard of these eagles using anything other than old mature dominate native trees within native forests. I recalled seeing gum tree leaves in a nest near Mweiga in 1978-79, and speculated then if they knew the insecticidal properties of this (then locally) tough to find exotic. Crowned Eagles will of course use eucalyptus and other exotic trees to perch in wherever these trees mingle with indigenous forests or bush. For the vast majority of plantation exotics in Kenya they are all characterised by sterility and as much biodiversity as a wheat field. These exotic forests have not had the time to stabilise and slowly allow habitation by enterprising wildlife pioneer settlers. Again these exotic forests support rural communities on their fringes and within their core who disturb the forests and probably keep such pioneer species out. I hear for example, that the Red breasted Sparrowhawk is very much at home in exotic plantations in South Africa, whereas in Kenya is has yet to be recorded in anything other than indigenous and now rare type of highland forests.