Yellow-billed divers
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Yellow-billed diver ( Gavia adamsii ) |
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| ( Gray , 1859) |
The Gelbschnabel divers or Gelbschnabel-loon ( Gavia adamsii ) is a species from the genus of loons ( Gavia ). The species breeds in the coastal tundra of Russia and North America and winters on northern coasts. As an exception, the yellow-billed diver can also be observed in Central Europe, especially in winter on the coasts of the North and Baltic Seas. The scientific species name honors the English marine doctor and naturalist Edward Adams (1824-1856).
description
The yellow-billed diver is the largest species in the genus Gavia . It reaches a body length of 77–90 cm and a wingspan of 135–150 cm. According to the few data available so far, the animals weigh 3.7–6.4 kg and are therefore significantly heavier than a gray goose .
The species is unmistakable in the magnificent dress . The basic color of the entire top and of the head and neck is black. The upper back shows dense rows of large white squares, the rear back and the flanks show fine rows of white dots. The neck has a transversely oval field of white longitudinal lines on the sides, and a narrow line of white dots on the throat. The chest, abdomen and the under wing coverts are pure white.
It is named after the large, light yellow or ivory-colored and slightly raised beak, which, when swimming, usually protrudes slightly diagonally upwards due to a corresponding head position. The legs and feet are gray. The iris is wine red.
In the plain dress , the entire upper side is dark gray, but wing-coverts with white speckles are often still present. The head and back of the neck are dirty light gray-brown, the dark color turns into white at the front of the throat and neck. There is a fairly large white area around the eye. The beak is pale gray, darker at the base and especially on the ridge. The forehead is raised steeply.
The youth dress is very similar to the plain dress, but the birds are generally more yellow-brown on the upper side, the contour feathers on the upper side and the flanks are also lightly edged and thus show a clean wave pattern. The beak is often not yet fully grown and is pale gray to light yellow.
Vocalizations
The flight calls resemble those of geese , like those of other loons . The district calls are far-reaching yodelling or howling. Warning sound is a deep laugh.
distribution and habitat
The range of the species includes the coastal tundra of Russia and North America. The Russian area extends from the Murman coast to the east to the Chukchi peninsula . In North America, the species occurs in central northern Canada and on the north coast of Alaska . During the breeding season the species inhabits inland waters in the lowlands.
nutrition
The food is hunted by diving and consists mainly of fish, in addition to frogs , crustaceans and molluscs . The droppings are deposited on the bank.
Reproduction
The yellow-billed diver pairs live monogamous for long periods of time, as is the case with other loons. The nests are built on the banks of the water and usually only consist of a hollow in the ground, which is sometimes also covered with parts of plants. Copulation happens on the bank without courtship behavior. except for mutual beak immersion. The eggs are laid in mid-June to mid-July. The clutch normally consists of two eggs. The breeding season lasts at least 27 days; the eggs are incubated by both parents and the chicks are then led together. If not fed enough, the young fight intensely, often only one survives.
hikes
Yellow-billed divers are apparently mainly medium to short-range migrants . Withdrawal from the breeding area is initiated when the young are fit to fly, approximately three months after arrival. The first overwinterers are observed as early as October. The Russian birds overwinter on the one hand on the northern Asian Pacific coast, on the other hand off the coast of Norway, but apparently also regularly in the northern Baltic Sea. The populations of North America overwinter off the American Pacific coast from southern Alaska to central California . The return to the breeding areas takes place from mid-May. The species is very rarely detected in Central Europe from October to April, especially on the coasts of the North and Baltic Seas and only in exceptional cases inland on larger lakes.
Existence and endangerment
The IUCN has classified the yellow-billed diver as a minor threat since 2010. Oil is extracted in large parts of both the breeding and wintering areas. Oil spills can therefore have negative inventory effects. This is especially true of the Alaskan population, where 90 percent of the population is breeding in a region dedicated to the extraction of oil and gas.
The yellow-billed diver is also partly hunted by the indigenous population in its range. There are different assessments of the extent to which this hunt poses a threat to this species.
literature
- Einhard Bezzel: Compendium of the birds of Central Europe. Nonpasseriformes - non-singing birds . Aula, Wiesbaden, 1985: pp. 17-18 ISBN 3-89104-424-0
- National Geographic Society: Field guide to the birds in North America . Washington, 1983.
- Lars Svensson , Peter J. Grant, Killian Mullarney, Dan Zetterström: The new cosmos bird guide. Kosmos, Stuttgart 1999, ISBN 3-440-07720-9 , p. 14 f.
- The reproductive behavior of the Yellow-billed Loon, Gavia adamsii . (With G. Ågren). The Condor 78: 454-463. 1976.
Web links
- Gavia adamsii in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2004. Retrieved on 23 November, 2008.
- Videos, photos and sound recordings of Gavia adamsii in the Internet Bird Collection
- Yellow-billed diver's feathers