Genetic analysis of migrant Siberian Chiffchaffs in Britain and Ireland

The criteria for robust identification of migrant Siberian Chiffchaffs Phylloscopus collybita tristis in western Europe continue to prove controversial. Whereas many 'classic' birds are identifiable on the basis of plumage and vocalisations, many others are less straightforward. This article describes a preliminary genetic analysis of three birds, two from Britain in autumn and one from Ireland in spring, which were trapped and identified as Siberian Chiffchaff. Mitochondrial cytb sequencing confirmed that all three were tristis.The results are discussed in light of the possibility of the occurrence of hybrids, and also genetic data from elsewhere in western and northern Europe.