THE REPRODUCTIVE BEHAVIOUR AND TAXONOMY OF HEMPRICH'S GULL LARUS HEMPRICHI

Abstract

SummaryObservations were made in the sea bird colonies of the Kiunga Archipelago in Kenya, in 1961. The islands are described and the numbers of the five species of sea birds (one gull and four species of terns) which were found breeding on the islands visited are recorded. The principal predators in the colonies are man and Hemprich's Gull Larus hemprichi.Particular attention was paid to the reproductive behaviour of hemprichi which is a tropical hooded gull with extensive areas of dark plumage. Dark plumage in gulls is disadvantageous to plunge‐diving for fish; hemprichi is almost entirely a scavenger. Hemprichi is not a social breeder and as a rule there is only one pair on each island. It is also relatively non‐territorial.In the most recent revision of the Laridae, hemprichi is classified as a “‘primitive’ hooded gull”, but in fact its behaviour complex is not characteristic of this group. The displays of hemprichi are described and compared in detail with the homologous displays of “primitive” hooded gulls, masked gulls and the large white‐headed gulls in the taxonomic sense.These displays are all except one (Facing Away) very similar to those of the Herring Gull L. argentatus (a large white‐headed gull). By treating the displays as taxonomic characters, it is concluded that hemprichi is a large white‐headed gull which has acquired a hood and dark plumage, this change being facilitated by its having become a scavenger (and thus not dependent upon white plumage as an adaptation to plunge‐diving), and by some other factor possibly connected with tropical insolation.Evidence is put forward which shows that the White‐eyed Gull L. leucopthalmus, another tropical hooded gull superficially similar to hemprichi, is also a large white‐headed gull.