| Northern Gannet | |
|---|---|
 Adult in flight. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Suliformes |
| Family: | Sulidae |
| Genus: | Morus |
| Species: | Morus bassanus |
The Northern Gannet, known simply as Gannet in Europe (Morus bassanus), is a large seabird in the family Sulidae.
Taxonomy[]
The Northern Gannet is a member of the gannet and booby family, Sulidae, which comprises 9 similar and closely related species. This family and three others were once included in the order Pelecaniformes, but have since been moved to an order of their own, Suliformes. The largest species, or Gannets, belong to the genus Morus, which includes the Northern Gannet, the Cape Gannet and the Australasian Gannet. Of these, the Northern Gannet is the largest, as well as the only one found in the Northern Hemisphere. The Boobies (genus Sula), are smaller, more colourful tropical and subtropical birds.
Description[]
| Measurements | |
|---|---|
| Length: | 85-97 cm (33.4-38 in) |
| Weight: | 2.3-3.6 kg (5-8 lbs) |
| Wingspan: | 165-180 cm (65-71 in) |
The Northern Gannet is the largest seabird of the North Atlantic, nearly matching a Canada Goose in size. The male is, on average, slightly larger than the female. The Gannet is unmistakable, with a streamlined body, a pointed bill, a short, pointed tail, and long, narrow wings. The adult has an almost entirely white plumage with black wingtips and a tinge of buff on the nape, which becomes more intense in the breeding plumage, especially in the male. The juvenile is mostly dark brown in colour, with a tiny white spot on the tip of every feather. The bird gradually becomes whiter with each molt, eventually reaching the mature plumage at 5 years of age.
3 year old immature.
The dagger-shaped bill is whitish with thin streaks of black, which correspond to the edges of the three plates that make up the upper mandible. The Gannet has no external nostrils: to reach the trachea, the air passes through orifices placed below the upper mandible. This ensures that water does not penetrate with excessive force into the nasal cavities when the bird dives into the sea at great speed. When temperatures are particularly high, the bird may open its bill and breathe directly through the mouth. On the throat, just below the bill, there is a thin stripe of bare black skin. The eyes are pale blueish-grey with light blue eye-rings, surrounded by a small black featherless "mask". They are placed slightly forward on the head, allowing the bird to scan the water surface without having to excessively tilt its head towards the ocean. The neck is quite long and very flexible, thanks to the structure of the eighth and ninth cervical vertebrae, which are able to slide slightly on each other. The wings are very long, narrow and pointed, and the tail has 6 feathers of decreasing length from the center to the sides. The Gannet has black legs and feet with four forward-facing toes, each with a thin blueish (female) or light green (male) longitudinal line. The feet, fully webbed, are used for swimming and landing, and, since they are abundantly vascularized, they have an important function during incubation, replacing the brood patches that are present in other bird species.
Voice[]
The Northern Gannet makes raucous sounds.
Behaviour[]
Like many other seabird species, the Northern Gannet becomes highly gregarious during the breeding season, when it gathers in large colonies, and spends the rest of the year on the high seas. The long, narrow wings of the Gannet make it an excellent flier, capable of soaring for hours with little effort but also of flying nimbly with relatively rapid wingbeats. It uses both its wings and its webbed feet to propel itself in the water. Since it has virtually no land predators, the Northern Gannet is not shy around humans, which has made it an easy prey for hunters in the past. It is also known to follow fishing boats at sea. Young Gannets may be preyed upon by birds such as Skuas and large Gulls, but the highly protective nature of the adults make the colonies hard to attack. The Northern Gannet has a lifespan of over 30 years.
Feeding[]
The Northern Gannet soars on its long wings, scanning the ocean below. Its excellent eyesight allows it to spot a fish at a distance of up to 50 m. Once it has spotted a potential prey item, the bird retracts its wings and dives into the water at up to 90 km/h of speed, reemerging with prey in its bill. The prey is caught from below, as the Gannet swims back towards the surface with its wings and webbed feet. A short pursuit may take place if the fish is not caught immediately. The Gannet may stay underwater from 5 to 20 minutes, and may reach up to 10 m of depth. Northern Gannets mostly hunt in groups, but may be seen hunting alone when far from the colony. The bird's diet comprises about 50 species of fish, most of which are between 2.5 and 3.5 cm long and live in large shoals near the surface. Herring and steenbras are usually its preferred prey, followed by cod, hake, whiting, haddock, sardines, mackerel, garfish and anchovies.
Breeding[]
In the middle of winter, or towards the end of the season depending on latitude, the Gannets return to the coasts where they breed, gathering in colonies of variable size, from a dozen couples to thousands. Older males reach the breeding grounds a few weeks earlier than their partners and occupy the same nesting site used the previous year, whilst younger birds breeding for the first time tend to arrive later to create new nests.
Northern Gannets are monogamous and mate for life. When the couples reunite, they engage in courtship rituals to strengthen their pair bond. The ritual starts with the male signaling his ownership of the nesting site to the rest of the colony, shaking his head from side to side, stopping from time to time with his bill pointed towards the nest or towards the female, who observes the scene from land or from above. During the first interaction between the two, the male may be rather aggressive and peck the female's nape, to which she turns away. The actual courtship display then begins, with the partners facing each other, chest to chest, with their wings spread; they then stretch their necks out, raise their bills high and clatter them against each other. In the final stage of courtship, the birds rub their necks together and eventually mate, with the male spreading his wings and biting his partner's nape to maintain balance on top of her. After mating, the two rub their necks together once again and preen each other.
Gannet colonies are very dense, and the nests are very close, being 60-80 cm away from each other. The nests of older couples are located in the centre of the colony, whilst younger couples are forced to nest in less favourable positions in the outskirts of the colony. Gannets, especially males, may become very aggressive when defending their nests. Nest building and repairing are carried out exclusively by the male, who collects feathers, seaweed, grass stems and other kinds of plant debris and arranges them in a 30-60 cm tall cup-like structure, which is cemented with mud and guano. The internal depression, which the bird creates by pressing with his chest and belly, is lined with materials similar to the main structure, but finer and softer. Once the nest is complete, the female lays a single pale blue egg, which weighs 105 g on average and whose shell is covered in a layer of limestone which, upon contact with the nest floor, assumes its blackish colour. Incubation lasts for about 44 days. The parents take turn incubating the egg: the father's turn lasts about 35 hours; the female's, about 30. To incubate, the adult wraps its webbed feet around the egg, with the abundantly vascularized membrane serving as a brood patch. When switching roles, the two birds engage in a greeting display that strengthens their pair bond. If the egg is lost, the female may lay another one.
Upon hatching, the Gannet chick is blind and covered in thin whitish down through which its black skin can be seen. It is completely depended on its parents, who take turns guarding and brooding it. Even after its first few weeks of life, when it no longer needs to be brooded, the chick is always accompanied by one of its parents until fledging. If left unattended, it may be killed by other Gannets or predated by other birds. During the first stages of its growth, the chick is fed small quantities of food frequently; after about a month, the portions become more substantial and less frequent, with feeding occurring 3 times a day. Stimulated by contact with the young's bill, the adults regurgitate food in the chick's mouth. The parents are constantly looking for food: their hunting trips may last up to 13 hours, and may take them hundreds of km away from the colony. The young's down gradually grows thicker and longer and is eventually replaced by the typical blackish juvenile plumage. After 3 months in the nest, the young Gannet is no longer fed by its parents and must take its first plunge into the ocean. At first, it mostly swims on the surface, learning to dive properly with time.
Distribution and habitat[]
The Northern Gannet is a strongly pelagic bird that only comes to land to reproduce. It nests on top of rocky or earthy cliffs by the sea, often alongside other seabirds such as Auks. The largest colonies are found in islands and other areas not frequented by land predators. It hunts in deep waters. It breeds along the northern coasts of the Atlantic Ocean in Europe and North America, and scatters around the ocean outside of the breeding season. Juveniles are particularly erratic, with those born in Europe reaching the coasts of northern Africa and, rarely, even the Mediterranean basin in winter, and those born on Canadian coasts wintering in Florida and the Mexican Gulf.