Demography of the Seychelles Black Paradise-flycatcher: considerations for conservation and reintroduction

Abstract

The Seychelles Black Paradise-flycatcher Terpsiphone corvina is currently listed as Critically Endangered, on the basis of small population and restricted range. Currently, there is only one self-sustaining population comprising c. 150–200 individuals on the 10km² island of La Digue (Republic of Seychelles, western Indian Ocean), and consequently the creation of additional island populations has been identified as essential to improve its conservation status. We quantified the annual breeding success, adult mortality and juvenile recruitment of the flycatcher on La Digue, monitored tri-weekly over a two-year period (June 1999–June 2001), to determine factors affecting population demographics and assess the implications for the reintroduction of populations to other islands. A total of 267 breeding attempts were recorded with c. 45% of the documented world population of pairs systematically monitored each year. On average, pairs attempted to breed three times in a 12-month period (range 0–6), although not all attempts were successful. Breeding success was consistently low between years: 62% of nests (controlling for observation time) and 17–19% of study territories failed to produce any fledglings in each respective 12-month period. Daily failure rates were generally higher during incubation than in the nestling period. Nests close to the forest edge were more likely to fail. The majority (143) of the 152 failed nesting attempts were consistent with depredation and were characterised by the disappearance of nest contents and sometimes by egg and chick remains and the disappearance of the adult female. Predators were identified at 13 nests: five (3.3%) were depredated by birds, and eight (5.2%) were depredated by mammals and/or reptiles: Rattus sp. were confirmed as predators. Video monitoring conducted at 14 nests also confirmed the endemic Seychelles bulbul Hypsipetes crassirostris as a nest predator. Adult mortality was c. 21% and alien predators (Rattus sp. and Felis cattus) were identified in causing adult mortality. However, in the majority of cases, reasons for adult mortality were unknown. Of the 52 marked fledglings that could have been recruited to the plateau population, 45% (23) were observed away from their natal territory c. 9–10 months after fledging, 25% (13) of which were confirmed as territory-holding individuals. We present a simple model to predict population growth using the above data, and discuss implications for the creation of additional self-sustaining populations on suitable islands.

Ostrich 2005, 76(3&4): 104–110