Young gannets in autumn plumage are brown, with many white flecks. With the passing of each season, they become progressively whiter, reaching the complete adult plumage in their fourth or fifth year.
Listen to the sound of Northern Gannet
Copyright remark: Most sounds derived from xeno-canto
|wingspan min.:||170||cm||wingspan max.:||192||cm|
|size min.:||85||cm||size max.:||97||cm|
|incubation min.:||42||days||incubation max.:||46||days|
|fledging min.:||84||days||fledging max.:||46||days|
The offshore islands and steep cliffs that appeal to gannets have sometimes been selected for lighthouses, and several gannetries were probably abandoned in the 19th and early 20th centuries because lighthouses were built on them.
Occupied year after year, a typical nest grows from a low collection of seaweed, sticks, moss, and debris into a substantial heap of feathers, fish skeletons, and droppings accumulated from many generations of nesters. Nests are usually 600 to 900 mm apart and form regular lines due to the hexagonal shape of each territory, an arrangement that allows the birds to pack the maximum number of nests into a given area.
Between late May and mid-June the female gannet lays a single bluish-white egg in the moss-lined hollow at the top of the nest. The parent birds take turns incubating, or warming the egg to hatch it, with their webbed feet. In the first week of July, the first young gannets emerge from their shells. Grey, naked, and helpless, the chick sprawls in the nest, whining like a puppy. It is tended carefully by its parents, and after about two weeks is covered with a protective coat of soft white down.
Until old enough to take to the ocean and fend for themselves, the young are fed by the parents. The young bird reaches deep into its parent’s throat for its meal of partially digested fish. After a few weeks, the parents regurgitate, or bring up, the partially digested fish near the nest, and the young gannet feeds without further aid.
Plumage begins to appear at about six weeks, and flight feathers are fully grown by September. Only after days of hesitation does the young bird half-fly, half-tumble in its first plunge from the rock ledges to the water below. A fledgling occasionally falls to the rocks and, if uninjured, heads for the ocean. Once in the water, the young gannet may live on body fat for days, until it masters the specialized and difficult art of plunge-diving for food.
Gannets do not always dive so spectacularly for food. When a shoal of fish is close to the surface, a bird may rise only about a metre before plunging again. Or it may occasionally beat its way over the surface with its wings and feet, head underwater to see the fish. Northern Gannets feed on herring, mackerel, capelin, sandlance, and squid.
About 444 000 Northern Gannets nest at 34 colonies on the European side of the Atlantic. There are six colonies in Iceland, with a total of 25 000 pairs. In the British Isles, including Ireland, the Shetland Islands, and the Faeroe Islands, there are 22 Northern Gannet colonies, for a total population of 189 700 pairs. The Northern Gannet became established in Norway in 1946, but there are only five colonies with a total population of 2 300 pairs. There is also a gannet colony in northern France, with 6 000 pairs.
The North American population of Northern Gannets is not very large as seabird populations go. There are approximately 87 900 breeding Gannets on the Atlantic coast of North America, all of which nest at six colonies in the Gulf of St. Lawrence and along the east coast of Newfoundland. Once their young leave the nest, the gannets return south and disperse along the coast from New England to the Gulf of Mexico.