Gabbiano reale

Identificazione

The male European herring gull is 60–67 cm (24–26 in) long and weighs 1,050–1,525 g (2.315–3.362 lb), while the female is 55–62 cm (22–24 in) and weighs 710–1,100 g (1.57–2.43 lb). The wingspan can range from 125 to 155 cm (49 to 61 in). Among standard measurements, the wing chord is 38 to 48 cm (15 to 19 in), the bill is 4.4 to 6.5 cm (1.7 to 2.6 in) and the tarsus is 5.3 to 7.5 cm (2.1 to 3.0 in). Adults in breeding plumage have a light grey back and upper wings and white head and underparts. The wingtips are black with white spots known as "mirrors". The bill is yellow with a red spot and a ring of bare yellow skin is seen around the pale eye. The legs are normally pink at all ages, but can be yellowish, particularly in the Baltic population, which was formerly regarded as a separate subspecies "L. a. omissus". Non-breeding adults have brown streaks on their heads and necks. Male and female plumage are identical at all stages of development, but adult males are often larger.<p>Juvenile and first-winter birds are mainly brown with darker streaks and have a dark bill and eyes. Second-winter birds have a whiter head and underparts with less streaking and the back is grey. Third-winter individuals are similar to adults, but retain some of the features of immature birds such as brown feathers in the wings and dark markings on the bill. The European herring gull attains adult plumage and reaches sexual maturity at an average age of four years.<p>At least in the south-west part of the Baltic Sea and surrounding areas, the European herring gull (L. argentatus) actually can be seen with yellow legs. They are not considered as a subspecies, since they regularly breed with grey/flesh-coloured legged herring gulls. The offspring may get yellow or normal-coloured legs. They must not be confused with the in general yellow-legged gull (L. michahellis), which are more common in the Mediterranean area, but single birds may reach more northern seas.<p>Adult European herring gulls are similar to ring-billed gulls, but are much larger, have pinkish legs, and a much thicker yellow bill with more pronounced gonys. First-winter European herring gulls are much browner, but second- and third-winter birds can be confusing since soft part colours are variable and third-year herring gull often show a ring around the bill. Such birds are most easily distinguished by the larger size and larger bill of European herring gull.<p>The European herring gull can be differentiated from the closely related, slightly smaller lesser black-backed gull by the latter's dark grey (not actually black) back and upper wing plumage and its yellow legs and feet.<p>The smaller silver gull is largely confined to Australia.

Tassonomia

Their scientific name is from Latin. Larus appears to have referred to a gull or other large seabird and argentatus means decorated with silver.<p>The taxonomy of the herring gull/lesser black-backed gull is contentious, with different authorities recognising between two and eight species[citation needed].<p>This group has a ring distribution around the Northern Hemisphere. Most adjacent populations interbreed; however, adjacent terminal populations do not.<p>The Association of European Rarities Committees recognises six species:<p>These taxa are classified as subspecies of Larus argentatus by some authorities such as the American Ornithologists' Union and Handbook of the Birds of the World. Others such as the Association of European Rarities Committees, British Ornithologists' Union, and the International Ornithological Union now regard them as one or two separate species.<p>Several other gulls have been included in this species in the past, but are now normally considered separate, e.g. the yellow-legged gull (L. michahellis), the Caspian gull (L. cachinnans), the Armenian gull (L. armenicus) and Heuglin's gull (L. heuglini).

Nome scientifico

Larus argentatus

Autorità

Pontoppidan, 1763

Ordine

Caradriformi

Famiglia

Laridae

Genere

Larus

Areale e habitat

Herring gulls breed in much of north-western Europe, including Iceland, the United Kingdom, Ireland and France. Since 2009, herring gulls in the United Kingdom have been on the red list of birds of conservation concern, including County Durham.<p>They have been recorded from all the coasts of Europe including the Mediterranean and occasionally inland. Vagrants have been recorded in Israel, Cyprus and Turkey.<p>Birds in France are mainly resident, but northern populations migrate in winter, generally to the coasts of north-western Europe.

Migrazione

Complete migrants

Comportamento

European herring gull flocks have a loose pecking order, based on size, aggressiveness, and physical strength. Adult males are usually dominant over females and juveniles in feeding and boundary disputes, while adult females are typically dominant when selecting their nesting sites.<p>The European herring gull has long been believed to have extremely keen vision in daylight and night vision equal or superior to that of humans; however, this species is also capable of seeing ultraviolet light. This gull also appears to have excellent hearing and a sense of taste that is particularly responsive to salt and acidity.<p>Parasites of European herring gulls include the fluke Microphallus piriformes.

Conservazione

Tendenza della popolazione

declining