What's so special about New Guinea birds?

Summary. I discuss why the tropical island of New Guinea has long been important in the development of our understanding of birds. There are two sets of reasons: New Guinea's birds, and its geography and peoples. New Guinea birds include: the famous birds of paradise, bowerbirds, and megapodes, which evolved in New Guinea (or New Guinea plus Australia) and are still concentrated there; pigeons, parrots, and kingfishers, which are especially species-rich and diverse in New Guinea and radiated there, whether or not they originally evolved there; and many groups that are morphologically and ecologically similar to European groups, such as ‘wrens’, ‘creepers’, and ‘nuthatches’, but that proved to be ‘lookalikes’ that evolved independently in New Guinea / Australia, just as numerous marsupial mammals and placental mammals converged on similar morphologies. Finally, the poisonous pitohuis and ifrit independently acquired the same neurotoxin as did South American poison-dart frogs; and a melampitta roosts and nests underground. The advantages offered by the island itself include: its equatorial location and its high mountains, so that New Guinea offers the entire range of habitats from coral reefs and rainforests through alpine grassland and glaciers on one short transect; the ‘right size’ (sufficient species to illuminate but not too many species so as to confuse); a simple geographic layout comprising a central mountain chain and its lowland ring; hundreds of islands of three types; virtually complete knowledge of the composition of its resident avifauna at the level of species; and the encyclopedic knowledge of birds among traditional New Guinea peoples. As examples of phenomena of general biological interest that New Guinea birds have illuminated, I discuss elevational sequences of congeners, culture in bowerbirds, evolution of ‘aggressive mimicry’ of larger bird species by smaller birds, brown-and-black mixed-species foraging flocks, and selection for and against overwater dispersal. These birds, landscapes, and topics are illustrated by photographs by K. David Bishop.