Northern gannet (Morus bassanus)-8211

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 Northeastern 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 northern 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 colored 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 color from dark grey to dark brown. There are colored 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.
Young bird with the front part of its body showing adult plumage.
Juveniles are dark brown.

Fledglings are dark grey to slate-grey with upperparts and wings finely speckled with white. There is a prominent V-shaped white area under the rump. The wing tips and tail are dark brown-black, partly tipped with white. The bill and iris are dark brown. They can weigh more than 4 kg (8.8 lb) by the time they leave the nest at about 10 weeks of age. In the second year, the bird's appearance changes depending on the different phases of moulting: they can have adult plumage at the front and continue to be brown at the rear. Gannets gradually acquire more white in subsequent seasons until they reach maturity after five years.

Northern gannets are slightly larger and thicker-billed than Cape or Australian gannets. The northern gannet has more white in the wings and an all-white tail, the other species having black tips to their tail feathers. Individuals on the west coast of Africa could be confused with vagrant masked boobies, though the latter is smaller overall, lacks the buff tinge to the head, and has a black tail. From a distance, or in poor visibility, albatrosses can be confused with northern gannets, particularly those with immature plumage that have more black on the wings.

Northern gannets have streamlined bodies adapted for plunge-diving at high speed, including powerful neck muscles, and a spongy bone plate at the base of the bill. The nostrils are inside the bill and can be closed to prevent water entry; the eyes are protected by strong nictitating membranes. There are subcutaneous air sacs in the lower body and along the sides. Other air sacs are located between the sternum and the pectoral muscles and between the ribs and the intercostal muscles. These sacs are connected to the lungs and are filled with air when the bird breathes in. The air can be returned to the lungs by muscle contractions.

The feathers are waterproof, which allows the birds to spend long periods in water. A water-impermeable secretion produced by a sebaceous gland covers the feathers and the birds spread it across their body using their beak or head. Individuals have a subcutaneous fat layer, dense down feathers and tightly overlapping feathers that help them withstand low temperatures. A reduced blood flow in the webbing on their feet outside of the breeding season also helps to maintain body temperature when the birds swim.

After the breeding season, adult northern gannets disperse over a wide area although they travel no more than 800 to 1,600 km (500 to 1,000 mi) from the breeding colony. It is not known if all birds from one colony migrate to the same over-wintering area. Many adults migrate to the west of the Mediterranean, passing over the Strait of Gibraltar and flying over land as little as possible. Other birds follow Africa's Atlantic coastline to arrive in the Gulf of Guinea. Immature northern gannets from colonies in Canada fly to the Gulf of Mexico, much further south than the adults. The immature gannets migrate southwards for great distances and have been recorded as far south as Ecuador. In their second year some birds return to the colony they were born in, where they arrive later than the mature birds. They then migrate south again at the end of the breeding season, but travel shorter distances in this second migration. Gannets from Alderney have been tracked since 2015 to gain better knowledge of their movements. One individual was found to have traveled from its colony in Alderney to Scandinavian waters, a round trip of around 2,700 km (1,680 mi).

The wings of the northern gannet are long and narrow and are positioned towards the front of the body, allowing efficient use of air currents when flying. Even in calm weather they can attain velocities of between 55 and 65 km/h (34 and 40 mph) although their flying muscles are relatively small: in other birds flying muscles make up around 20% of total weight, while in northern gannets the flying muscles are less than 13%. Despite their speed, they cannot manoeuvre in flight as well as other seabirds. Northern gannets need to warm up before flying. They also walk with difficulty and this means that they have problems getting airborne from a flat area. They take off from water by facing into the wind and strongly beating their wings. In light winds and high waves they are sometimes unable to take off and they can become beached.

For more information, please visit en.wikipedia.org/wiki/Northern_gannet

Taken on: October 15, 2020

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