Population sizes and the status of endemic and restricted-range birdspecies on Sangihe Island, Indonesia

Abstract

The island of Sangihe, Indonesia, was visited in 1998–99 with theaim of producing population estimates of the island's endemic and otherrestricted-range bird species, some of which were poorly known and thoughtto be at risk of extinction due to habitat change. The study focused on thelast remaining patch of primary forest, on MountSahendaruman in southern Sangihe, home to three critically endangeredendemic species: Cerulean Paradise-flycatcher Eutrichomyiasrowleyi, Sangihe Shrike-thrush Colluricincla sanghirensis,and Sangihe White-eye Zosterops nehrkorni. Population densitieswere estimated from primary forest and secondary habitats across Sangihe toassess species dependency on primary habitat. Twenty of 24restricted-range, globally threatened or endemic taxa were recorded anddensity estimates were calculated for 15 of these. The endemic Red-and-blueLory Eos histrio is extinct on Sangihe as a result of lowlandforest loss. Six species (Nicobar Pigeon Caloenas nicobarica,Sulawesi Dwarf Kingfisher Ceyx fallax, Golden Bulbul Ixosaffinis, E. rowleyi, C. sanghirensis, and Z. nehrkorni) wereeither not recorded or have verysmall populations and are critically endangered on Sangihe; two species ofTanygnathus parrot are also facing local extinction on the island.The major threat to all these species is the destruction of primary forest;larger species are also threatened by hunting. The remaining endemic andrestricted-range species (Blue-tailed Imperial Pigeon Duculaconcinna, Sangihe Hanging-parrot Loriculus catamene, SangiheScops-owl Otus collari, Lilac-cheeked Kingfisher Citturacyanotis and Elegant Sunbird Aethopyga duyvenbodei) were morewidespread and occurred in secondary habitats. I recommend that L.catamene and A. duyvenbodei, currently treated as globallyendangered, be reclassified as near-threatened and vulnerable respectively because of their large populationsand tolerance of disturbed habitats. Species with wide global ranges thatare represented by endemic subspecies have the greatest tolerance fordisturbed habitat. The widespread deforestation of Sangihe has had seriousconsequences for many bird species and today the island supports the mostthreatened assemblage of single-island endemic species in Indonesia.Species-specific research to determine the status and ecology of E.rowleyi, C. sanghirensis and Z. nehrkorni, and monitoring ofthe Sahendaruman forest are desperately needed as a basis for futureconservation efforts.