Since Ernst Mayr defined species in 1942 (1), classifying swiftlets (Aves, Collocaliini) into taxonomic groups has presented a major challenge. The glossy swiftlets represent some of the most taxonomically challenging and relatively under-studied birds in the family Apodidae. The appearance of white-bellied glossy swiftlets (the Collocalia esculenta group) is somewhat unremarkable. They all have dark, black plumage with a green or blue gloss. Until recently, phenotypic characters were used to separate the species of white-bellied […]