Stable-hydrogen isotope analyses suggest natural vagrancy of Baikal Teal to Britain

Stable-hydrogen isotope signatures of feathers from a first-winter Baikal Teal Anas formosa collected in Essex in January 1906 reveal marked differences between juvenile feathers, grown on the breeding grounds, and post-juvenile feathers, grown on the wintering grounds.The natal-area signatures were consistent with a Siberian origin and the wintering-area signatures were consistent with a west European origin.This suggests that the Essex bird originated within the normal breeding range of Baikal Teal and that its occurrence in Britain was the result of natural vagrancy.