alcatraz común (Morus bassanus) northern gannet

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 la...
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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
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