Status of the form barabensis within the Larus argentatus-cachinnans-fuscus complex

Between 19th July and 1st August 1997, at the Chany Lakes in southwestern Siberia, data were collected on phenotype features and behaviour of the local populations of gulls Larus belonging to the taxonomically vague form barabensis. These were compared with data from the literature and museum material on the morphological, oological and behavioural characters of L. c. cachinnans and L. (fuscus?) heuglini, as well as those of some other related gull forms. In size, proportions and coloration, barabensis most closely resembles heuglini, while also showing some admixture of cachinnans characters. The authors conclude that barabensis is a well-defined taxon that has arisen as a result of introgression by cachinnans genes into heuglini populations as the latter expanded their range southwards. They suggest that barabensis be treated as a subspecies of L. heuglini unless the latter's status as specifically distinct from Lesser Black-backed Gull L. fuscus is proven to be unwarranted.