Interbreeding of little and fairy terns

Abstract

Before 1968 the Little Tern Sterna albifrons and the Fair Tern S. nereis were thought to be allopatric breeders. Since then, overlap of their breeding ranges has been establishelbetween Gulf St Vincent, SA, and eastern Bass Strait. Inter- breeding in the former region occurred in 1975 and probably before. S.albifrons sinensis and S.nereis nereis are probably the progeny of isolated breeding populations of common ancestry. Where the breeding range of the former has recently overlapped that of the latter, interbreeding may occur, perhaps when a bird lacks a mate of the same species.