The distribution and population of Seychelles Black Paradise-flycatcher Terpsiphone corvina on La Digue: implications for conservation and translocation

摘要

The 10 km~2 island of La Digue, Republic of Seychelles, western Indian Ocean supports the last viable population of the Critically Endangered Seychelles Black Paradise-flycatcher Terpsiphone corvina. Small populations recorded on adjacent islands since the 1980s appear to be ephemeral and not self-sustaining. We document the results of the first island-wide survey of the flycatcher on La Digue using the playback of conspecific calls at random points. Previous surveys were based largely on counting the number of singing males. The survey was conducted between April and August 2001 and confirmed (i) the current world population is at least 200 individuals (109-145 territories, 218-290 individuals) in a c. 4.4 km~2 range, thus accurately quantifying the documented increase in flycatcher numbers since the late 1980s; (ii) territories were more widely distributed than previously recorded and not exclusively associated with coastal plateaux or freshwater bodies, contrary to previous descriptions; and (iii) distribution was determined largely by the presence of high canopy (native) broad-leaved tree species. The importance of canopy height to flycatchers was highlighted by the fact that localized loss of high canopy (native )forest (4%), in a 161 ha study area on the large western plateau, resulted in an equivalent reduction (4%) in the number of territories. In light of our findings we discuss the implications for conservation of the flycatcher on La Digue and its possible translocation.