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Genetics reveal Katiti’s past: An article on the Seychelles Kestrel by Liz Wambui

March 22nd, 2011 · No Comments · Raptor Research

A Seychelles Kestrel on a nest. Photo by Jeff Watson

Katiti in Creole, crashed to approximately eight individuals since the 1940s before the population recovered, apparently unassisted, a genetics study published in the October 2009 Biological Conservation Journal has revealed. This crash, it is thought, approached the severity of the genetic bottleneck of the Mauritius Kestrel whose numbers reduced to only four known individuals in the wild in the early 1970s. Intriguing however, is that the Seychelles Kestrel seems to have recovered undetected and without intensive intervention. Methods to measure levels of genetic diversity in ancestors have improved to allow pinpointing of major changes in a population’s history. Using genetic data from 100-150 year-old museum specimen, and comparing this with data from current populations, the study established that at one point the population crashed. And then with very little conservation effort it recovered. Nirmal Shah, Chief Executive of Nature Seychelles, was part of the study led by Kent and Sheffield Universities in the UK. A clear understanding of the recent population history of a species is important because it helps managers to anticipate problems associated with a dip in population. Island endemic bird populations generally have lower levels of genetic diversity than species with a continental distribution. This increases inbreeding and its associated risks of extinction. Inbreeding causes problems such as lowered reproductive fitness and vulnerability to disease. Preservation of genetic diversity is thus the basis of many conservation efforts because diversity is vital for evolutionary adaptation, and adaptation is key to the long-term survival of any species. Therefore, interventions on behalf of endangered birds on islands usually involve boosting population sizes in order to vary the genetic material. This has been true for species action for most of Seychelles endemics including the Seychelles Magpie robin Copsychus sechellarum (Pi Santez in Kreol) and Seychelles warbler Acrocephalus sechellensis (Timerl Dezil). In the past, conservation efforts relied on historical accounts and some anecdotal data. Historical records have variously described the Seychelles Kestrel as “tolerably common” in the 1860s, “frequently seen in all islands” in the 1930s, both “well distributed” and “rare” in the 1950s, “Critically Endangered and close to extinction” by 1966, with “probably less than 30 birds” confined to Mahe in 1969.

 

Seychelles Kestrel Chick. Photo by Jeff Watson

Surveys in 1973 located 49 pairs and estimated a population of 150-300 birds and by 1981, there was an estimated carrying capacity of 370 pairs. In 1985, the Katiti was described as being “far more numerous than previously thought”. Surveys in 2000-2001 suggest that the population remained stable in the previous 25 years. Although genetic data can help show changes, it does not explain why the changes occurred. Habitat loss, development and fires as well as predation and competition by introduced species is thought to have caused the decline of the Katiti. Kestrels were also killed because they stole chickens and were thought to be a bad omen. The Seychelles Kestrel recovery from a severe population bottleneck relatively unaided by intensive conservation efforts is extremely rare. Many seemingly comparable ‘unmanaged’ species recoveries can often be explained by indirect intervention, such as broad-scale ecosystem management. But the study bears a note of caution. “Given the current pressure on global conservation resources, this recovery may appear encouraging. However, outcomes such as this are likely to be the exception rather than the rule for other endangered island endemics.” Source: Natureseychelles/Zwazo – Seychelles Conservation Magazine Number 21 2. Katiti: Myths unfurl Professor Massimo Pandolfi and Dr. Michele Barilari from Urbino University –Italy which has an MOU with Nature Seychelles have for the last couple of years been conducting research on Seychelles Kestrel (Katiti). Here they give a sneak preview of their stirring findings exploring the diverse myths on this inimitable bird of prey. The Seychelles Kestrel (Katiti in Creole) is endemic to the granitic Seychelles and little is known about its ecology and behaviour. Its ancestors came from Africa and Madagascar and the life in small and isolated islands, principally covered by a wide and deep tropical forest, made it a tiny raptor (no more than 90 g, the smallest kestrel in the world) with wide wings and long tail like Sparrow hawks. The life on the Seychelles forest changed not only its aspect, but transformed deeply its behaviour from a grassland hunter into a small raptor able to move and hunt inside dense forests. The low detectability of the Katiti, due to the nature of its habitat and behaviour, makes difficult the observation and the study of this bird, but the high conservation value of the species (classified as Threatened by IUCN) and its importance in the Seychelles ecology motivated us to spend long hours searching for this enigmatic bird in the forests of Seychelles. The Katiti today has a world population of only 350 pairs and the distribution of the species is not uniform in the archipelago: the largest part of the population (near 300 pairs) is confined to Mahè and Satellite islands, 40-50 pairs on Silhouette, only a few pairs in North and Praslin. At the beginning of the century the Seychelles Kestrel was extinct on Praslin till the reintroduction of 13 birds in 1977. During the following years the population reached 10 pairs (Watson, 1989), but recent studies (2003), carried out by Nature Seychelles, demonstrate that the reintroduction was not a complete success because on the island were present only 6 pairs and most of them were not attempting to nest or failed in the first phase of the breeding season. An island of the size of Praslin could be expected to hold more than 90 pairs, based on observation of the Mahè population done by Dr. J. Watson in 1980. We can wonder now if some ecological aspects of Praslin could be a limiting factor for the local population or if the reduction of the population is the result of a normal dynamic (statistical fluctuations) of a small and (almost) isolated population. A study group of the Urbino University directed by the ornithologist M. Pandolfi began to follow the Katiti with a first survey on Silhouette in 2004 where, with the help of Justin Gerlach, some observations on the species were done and blood samples for the genetic evaluation collected. Later, in 2006-2007, another survey was done in Mahè analyzing the distribution and the ecological preferences of the Katiti population in two different, forest and urban, areas.

 

Seychelles Kestrel with prey. Photo by Johan van der Watt

In 2008, with the collaboration of Dr. Nirmal Shah and Nature Seychelles, a group of us, Massimo Pandolfi and Michele Barilari, with three Master thesis students of the Urbino University, Diego Tarini, Carlotta Di Biase and Emily Pasquini, began a study on the critical Katiti population of Praslin with the aim to characterize which causes determine the different dynamics of the population between Mahè and Praslin. In the study we are trying to evaluate which ecological parameters might be limiting factors in the Praslin population. The distribution and breeding success of the pairs and some ecological parameters (and potential limiting) factor as predation, inter-specific competition, prey and nest site availability are being analyzed. In order to evaluate the predation pressure on the island, we placed “eggs models” in artificial cavities. Eggs models were made by moulding plasticine that retains impression of the bill or teeth of the predator aiding the identification. Plasticine eggs have been located in different habitat: forest, urban and sub-urban. Predation index was calculated as number of artificial cavities predated/days of exposure. Relative abundance of the main katiti preys, Green Day Gecko (Phelsuma sppl.) and Skinks (Mabuya secellensis), was evaluated with a Phelsuma index (scanning with binoculars 100 trees in each territory at a distance of 30m). The height from the ground of the single geckoes on the trees had been evaluated too. Skinks abundance was evaluated with transects of 500m x 3m in different habitat. We evaluated the local density of a nest site competitor and potential nest predator too, the Indian Mynah (Acridotheres tristis). Plots (300m radius) with a 10 minutes of observation had been realized. Once we characterize the distribution of the population and the limiting factor/s on Praslin we will underline a conservation program to increase the critically endangered population of Praslin.

This article has been reproduced by kind permission of Liz Wambui and Nature Seychelles.

Source: Nature Seychelles/Zwazo – Seychelles Conservation Magazine Number 19

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