Andean Gull

Description

The Andean gull (Chroicocephalus serranus) is a species of gull in the family Laridae. As is the case with many gulls, it has traditionally been placed in the genus Larus. It is found in the Andes in mountainous regions of Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is unusual for a gull in that it breeds inland in mountain areas. It may be variously found around rivers, freshwater lakes, saline marshes, and pastureland. At 45–48 cm (18–19 in) long, the Andean gull is large for a black-headed gull (it is the largest gull with that kind of plumage in the Americas). It is the largest species in the genus Chroicocephalus and has a dark hood, a pale grey back and a pattern of black and white on its primaries. The Andean gull is known from Chile, Peru, Argentina, Bolivia, Ecuador and Colombia where it breeds in mountainous areas, usually at elevations of over 3,000 metres (9,800 ft). In areas with harsh winters it migrates to lower elevations in winter, sometimes as far as the coast. Flocks of these gulls are common on the coast in southern Peru and northern Chile, but It has yet to be established where these particular birds breed. In the wetlands of the Altiplano it is resident and breeds at 4,000 metres (13,000 ft) while in southern Argentina it may breed at as little as 2,000 metres (6,600 ft) but this is in similar habitats to the birds further north. The Andean Gull nests in small scattered colonies, sometimes even as solitary pairs, in small, isolated ponds. Unusually for a gull of this size, it becomes sexually mature at the age of two years rather than three. It feeds on a variety of prey items, including insects and worms taken on fields and grasslands; it also sometimes catches aerial insects and eats some garbage when available. Chroicocephalus is a genus of medium to relatively small gulls which were included in the genus Larus until recently. Some authorities also include the Saunders's gull in Chroicocephalus. The genus name Chroicocephalus is from Ancient Greek khroizo, "to colour", and kephale, "head". Representatives of this genus are found in regions/subregions all over the world, each species usually being confined to a region.