Gaviota Sombría

Identificación

The lesser black-backed gull is smaller than the European herring gull. The taxonomy of the herring gull / lesser black-backed gull complex is very complicated; different authorities recognise between two and eight species. This group has a ring species distribution around the Northern Hemisphere. Differences between adjacent forms in this ring are fairly small, but by the time the circuit is completed, the end members, herring gull and lesser black-backed gull, are clearly different species. The lesser black-backed gull measures 51–64 cm (20–25 in), 124–150 cm (49–59 in) across the wings, and weighs 452–1,100 g (0.996–2.425 lb), with the nominate race averaging slightly smaller than the other two subspecies. Males, at an average weight of 824 g (1.817 lb), are slightly larger than females, at an average of 708 g (1.561 lb). Among standard measurements, the wing chord is 38 to 45 cm (15 to 18 in), the bill is 4.2 to 5.8 cm (1.7 to 2.3 in), and the tarsus is 5.2 to 6.9 cm (2.0 to 2.7 in). A confusable species is the great black-backed gull. The lesser is a much smaller bird, with slimmer build, yellow rather than pinkish legs, and smaller white "mirrors" at the wing tips. The adults have black or dark grey wings (depending on race) and back. The bill is yellow with a red spot at which the young peck, inducing feeding (see fixed action pattern). The head is greyer in winter, unlike great black-backed gulls. Annual moult for adults begins between May and August and is not complete on some birds until November. Partial prebreeding moult occurs between January and April.<p>Young birds have scaly black-brown upperparts and a neat wing pattern. They take four years to reach maturity. Identification from juvenile herring gulls is most readily done by the more solidly dark (unbarred) tertial feathers.<p>Their call is a "laughing" cry like that of the herring gull, but with a markedly deeper pitch.

Taxonomía

The lesser black-backed gull was one of the many species originally described by Carl Linnaeus in his 1758 10th edition of Systema Naturae, and it still bears its original name Larus fuscus. The scientific name is from Latin. Larus appears to have referred to a gull or other large seabird, and fuscus meant black or brown.<p>The five recognized subspecies are:

Nombre científico

Larus fuscus

Autoridad

Linnaeus, 1758

Orden

Charadriiformes

Familia

Láridos

Género

Larus

Distribución y hábitat

Lesser black-backed gulls have expanded their range westwards, first colonising Greenland in the 1980s. The species has not yet bred in the United States, although hybrid pairs with American herring gulls have been recorded twice.

Área de cría

PAL : Greenland, Iceland, w Europe to nc Siberia

Área no reproductiva

to sw Europe, wc, ec Africa, nw India, and e North America

Migración

Complete migrants

Conservación

Tendencia poblacional

rising