Colour aberrations in extinct and endangered birds

Abstract

Several groups of birds have suffered high extinction rates, especially rails, pigeons, parrots and passerines. Some island species that disappeared in the early 19th century, e.g. Lord Howe Gallinule Porphyrio albus, Rodrigues Parakeet Psittacula exsul and Mascarene Parrot Mascarinus mascarinus, are known from only a few skins and illustrations, whereas the Huia Heteralocha acutirostris of New Zealand is known from hundreds of specimens. Furthermore, two North American species—Passenger Pigeon Ectopistes migratorius and Carolina Parakeet Conuropsis carolinensis—which became extinct in the early 20th century, are also represented by hundreds of specimens. Other supposedly extinct bird species are enigmatic. Confusion exists concerning the unique specimens of Sharpe’s Rail Gallirallus sharpei and Townsend’s Bunting Spiza townsendi, paintings of a parrot from the West Indies and an aberrant white Huia, as well as aberrant specimens of the Critically Endangered Kakapo Strigops habroptilus. Much has been written concerning these birds and why they became extinct, or have become extremely rare, but few data are available concerning colour aberrations in certain specimens; the literature is also riddled with incorrect terminology. This paper addresses this shortfall and describes the various colour aberrations in these extinct and endangered birds and why they have occurred.