The island of Sangihe, Indonesia, was visited in 1998–99 with the aim of producing population estimates of the island's endemic and other restricted-range bird species, some of which were poorly known and thought to be at risk of extinction due to habitat change. The study focused on the last remaining patch of primary forest, on Mount Sahendaruman in southern Sangihe, home to three critically endangered endemic species: Cerulean Paradise-flycatcher Eutrichomyias rowleyi, Sangihe Shrike-thrush Colluricincla sanghirensis, and Sangihe White-eye Zosterops nehrkorni. Population densities were estimated from primary forest and secondary habitats across Sangihe to assess species dependency on primary habitat. Twenty of 24 restricted-range, globally threatened or endemic taxa were recorded and density estimates were calculated for 15 of these. The endemic Red-and-blue Lory Eos histrio is extinct on Sangihe as a result of lowland forest loss. Six species (Nicobar Pigeon Caloenas nicobarica, Sulawesi Dwarf Kingfisher Ceyx fallax, Golden Bulbul Ixos affinis, E. rowleyi, C. sanghirensis, and Z. nehrkorni) were either not recorded or have very small populations and are critically endangered on Sangihe; two species of Tanygnathus 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 and restricted-range species (Blue-tailed Imperial Pigeon Ducula concinna, Sangihe Hanging-parrot Loriculus catamene, Sangihe Scops-owl Otus collari, Lilac-cheeked Kingfisher Cittura cyanotis and Elegant Sunbird Aethopyga duyvenbodei) were more widespread and occurred in secondary habitats. I recommend that L. catamene and A. duyvenbodei, currently treated as globally endangered, be reclassified as near-threatened and vulnerable respectively because of their large populations and tolerance of disturbed habitats. Species with wide global ranges that are represented by endemic subspecies have the greatest tolerance for disturbed habitat. The widespread deforestation of Sangihe has had serious consequences for many bird species and today the island supports the most threatened 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 of the Sahendaruman forest are desperately needed as a basis for future conservation efforts.
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