The Northern gannet (Morus bassanus) is a large seabird native to the coasts of the Atlantic Ocean. It is the largest gannet and the largest seabird native to the western Palearctic. Northern gannets are known for making high-speed dives into the sea when hunting for fish. Because they are conspicuous and common throughout their native range, they are referred to in several ancient myths and legends.
The plumage of the Northern gannet 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 are surrounded by black bare skin and have a cobalt blue orbital ring, the iris is light blue-grey with a fine dark outer ring. 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 the legs. These are typically greenish-yellow in males and bluish in females and probably have a role in mating. 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. 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 breed in Western Europe, North America, and the Caribbean. Many adults migrate to the west of the Mediterranean, passing over the Strait of Gibraltar. 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, and have been recorded as far south as Ecuador. Northern gannets spend most of their time in the ocean coming on land only to breed and raise their chicks. They nest on cliffs overlooking the ocean or on small rocky islands.
Northern gannets are gregarious birds that breed in large colonies and forage in groups at sea. They are fast and powerful flyers, but may also glide for hours, barely flapping their wings. Despite their speed, they cannot maneuver in flight and 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 the 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. Northern gannets forage for food during the day, generally by diving at high speed into the sea. They search for food both near their nesting sites and also further out to sea. They forage from heights of up to 70 m (230 ft) and typically dive from between 11-60 m (36-197 ft). They dive with their bodies straight and rigid, wings tucked close to the body but angled back, extending beyond the tail, before piercing the water like an arrow. They control the direction of the dive using their wings and tail and fold their wings against the body just before impact. Gannets usually push their prey deeper into the water and capture it as they return to the surface. When a dive is successful, they swallow the fish underwater before surfacing and never fly with the fish in their bill. Northern gannets also forage for fish while swimming with their head underwater. These are loud and vocal birds, particularly in the colony. Their typical call is a harsh arrah-arrah or urrah-urrah, which is emitted upon arriving or when challenging other gannets at the colony.
Northern gannets are carnivores (piscivores) and fish form the bulk of their diet. They mainly feed on sardines, anchovies, haddock, smelt, Atlantic cod, and other shoal-forming species.
Northern gannets are monogamous and form long-lasting pair bonds. The oldest birds usually return to the breeding colonies first. Males try to attract an available female after establishing a territory. The females will fly over the colony several times before landing. Their posture, with the neck, stretched out, tells the male that they are available for courtship. The males will then shake their heads in a similar way to when they are guarding their nest, but with their wings closed. Mated pairs engage in a fencing display when the male arrives back at the nest. The two birds stand breast to breast with wings spread and bills extended vertically. They fence and scissor with their bills rapidly, calling loudly at the same time. Fencing is interspersed with bill bowing. Nesting starts in March or April; during this time Northern gannets become very aggressive and confrontations normally occur only between birds of the same sex. The preferred nesting sites are on coastal hillsides or cliffs. If these are not available Northern gannets will nest in groups on islands or flat surfaces. Nests are made from seaweed, plants, earth, and debris from the sea. The males usually collect the materials. Nests are compact cups typically 30-60 cm (12-24 in) in height. The female lays one egg and incubates it within 42-46 days; during this time the egg is surrounded by the brooding bird's warm, webbed feet. The newly hatched chick is featherless and is dark blue or black in color. It is fed regurgitated semi-digested fish by the parents and is only rarely left alone. The adults feed their offspring for around 13 weeks, right up until the time it leaves. The chick fledges between 84-97 days old and becomes reproductively mature at 4 to 5 years of age.
Although Northern gannet populations are now not threatened globally, their numbers were once greatly reduced due to loss of habitat, removal of eggs, and killing of adults for their meat and feathers. Today, these birds are frequently killed as bycatch in fisheries and are still hunted for food in some areas of their range.
According to the IUCN Red List, the total Northern gannet population size is approximately 1,500,000-1,800,000 mature individuals. In Europe, the breeding population consists of 683,000 pairs, which equates to 1,370,000 mature individuals. Overall, currently, Northern gannets are classified as Least Concern (LC) on the IUCN Red List and their numbers today are increasing.
