Recent changes in distribution and plumage phenologies of the White-winged Tern (Chlidonias leucopterus) in the Middle East

Changes in species geographic distributions, including those of migration routes, stopover sites, and over-wintering grounds, may affect the phenology of breeding and moult. The White-winged Tern (Chlidonias leucopterus) is a long-distance migrant which breeds in Eurasia and winters in Africa and Australasia. This species is known in the Eastern Mediterranean and the Middle East mainly during the migration seasons although it also breeds locally in eastern Turkey and the Persian Gulf. However, in the last decade, there has been an apparent change in the winter distribution of this species, with increasing observations of individuals during December–February in the Middle East, many of them in breeding plumage. Using data collected from specimens stored at the Natural History Museum at Tring (UK), ringing data from Israel, the online database eBird, and accompanying Macaulay Library (Cornell Lab of Ornithology), we described these recent changes in the seasonal distribution and annual moult cycles. While the birds that breed in the north begin to replace their black body feathers immediately at the end of the breeding season, the birds described here displayed the black body plumage (breeding plumage) throughout the winter (December–February), a plumage pattern that is offset by seven to eight months from those of the northern-hemisphere breeding populations. This might suggest yet-to-be discovered local breeding in the Middle East in February–April. In such cases as this, we hypothesize that examination of plumage phenology may help researchers investigate the timing of as yet unknown breeding phenology.