alcatraz común (Morus bassanus) northern gannet

The northern gannet (Morus bassanus) is a seabird, the largest species of the gannet family, Sulidae. It is native to the coasts of the Atlantic Ocean, breeding in Western Europe and North America. The sexes are similar in appearance. The adult northern gannet has a mainly white streamlined body with a long neck, long and slender wings. It is 87–100 cm (34–39 in) long with a 170–180 cm (67–71 in) wingspan. The head and nape have a buff tinge that is more prominent in breeding season, and the wings are edged with dark brown-black feathers. The long pointed bill is blue-grey, contrasting with black bare skin around the mouth and eyes. Juveniles are mostly grey-brown, becoming increasingly white in the five years it takes them to reach maturity.

Nesting takes place in colonies on both sides of the north Atlantic, the largest of which are at Bass Rock (75,000 pairs as of 2014), St Kilda (60,000 pairs as of 2013) and Ailsa Craig (33,000 pairs as of 2014) in Scotland, Grassholm in Wales, and Bonaventure Island (60,000 pairs in 2009) off the coast of Quebec. Its breeding range has extended northward and eastward, colonies being established on Russia's Kola Peninsula in 1995 and Bear Island, southernmost island of Svalbard, in 2011. Colonies are mostly located on offshore islands with cliffs, from which the birds can more easily launch into the air. The northern gannet undertakes seasonal migrations and hunts for the fish that form the bulk of its diet by high-speed dives into the sea.

The gannet was previously hunted for food in parts of its range, and the traditional practice still continues in the Outer Hebrides of Scotland and the Faroe Islands. It faces few natural or man-made threats, and since its population is growing it is considered to be a least-concern species by the International Union for Conservation of Nature (IUCN). As a conspicuous and common bird, it has been mentioned in several ancient myths and legends.
An adult northern gannet has a 170–180 cm (67–71 in) wingspan, and is 87–100 cm (34–39 in) long and weighs 2.3–3.6 kg (5.1–7.9 lb),making it the largest gannet and the largest seabird native to the western Palearctic. The two sexes are generally of a similar size and appearance.The plumage is white with dark brown to black wing tips; the primary flight feathers, primary coverts and alulae are dark. The head and neck are tinged buff-yellow, becoming much more prominent in the breeding season. Males are more deeply coloured than females.The eyes have a light blue to light grey iris surrounded by a thin black ring of bare skin.The beak is long, strong and conical with a slight downcurve at the end and a sharp cutting edge. In adults, the beak is blue-grey with dark grey or black edges. There is a black groove running the length of the mandible that merges into the skin around the eyes. A black band of bare skin also separates the pale feathers of the forehead and throat from the bill, which gives the gannet its distinctive face markings. The four-toed feet are joined by a membrane that can vary in colour from dark grey to dark brown. There are coloured lines running along the toes that continue along up the legs. These are typically greenish-yellow in males and bluish in females and probably have a role in mating.
Read less