Species limits in the Golden Bulbul Alophoixus (Thapsinillas) affinis complex

The Golden Bulbul Thapsinillas affinis of the Moluccan islands, Sula archipelago, Banggai islands, Togian islands and Sangihe, Indonesia, was until recently treated in Alophoixus before being placed in the resurrected genus Thapsinillas and shortly afterwards split into Northern and Southern Golden Bulbuls T. affinis and T. longirostris, but with a general consensus that a break-up into more species was required. We used plumage and morphometric analysis of museum specimens, supplemented by vocal samples, to determine where new species limits might be drawn. We found that the nine generally accepted subspecies break down into seven full species, five monotypic and two with two subspecies each: T. chloris on Morotai, Halmahera and Bacan (small, featureless; undifferentiated olive-green lores and ear-coverts, blackish base to submoustachial area; song reportedly a ‘jumbled babbling’); T. lucasi on Obi (round yellow lores, yellow-tinged ear-coverts, seemingly simple often squeaky-toy-like vocalisations); T. affinis on Seram with race flavicaudus on Ambon (larger than previous two, with half-wedge yellow lores, broad yellow tips to tail, song a group of strong rich flat whistles); T. mysticalis on Buru (half-wedge yellow lores, partial yellow eye-ring, olive-green underparts, olive-grey tail, whistled phrases recalling domestic canary); T. longirostris on Sula with race harterti on Peleng and Banggai (longest-billed, large, undifferentiated olive-green lores, song a loud jumble); T. aurea on the Togian islands (golden-yellow underparts, vague half-wedge yellow lores, blackish frontal supercilial line, yellow-tinged rump, song seemingly more complex than in longirostris) and T. platenae on Sangihe (vivid yellow chin and submoustachial area to throat and breast, bright yellow triangular lores, almost-complete yellow eye-ring, song seemingly simple and nasal). Comprehensive vocal sampling and molecular work may shed light on the origins and colonisation routes of this geographically unusual cluster of species.