Black guillemot

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Black guillemot
Black guillemot (Cepphus grylle)

Black guillemot ( Cepphus grylle )

Systematics
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Alkenbirds (Alcidae)
Genre : Cepphus
Type : Black guillemot
Scientific name
Cepphus grylle
( Linnaeus , 1758)
Black Guillemots, Elliston.jpg

The black guillemot ( Cepphus grylle ), occasionally even Teiste called, is a medium-sized bird of the family of Auks . They are agile fliers who often return to their breeding site from high altitude. They find their food by diving. There are five poorly differentiated subspecies.

In Central Europe , the nominate form Cepphus grylle grylle is a regular guest bird on the Baltic coast of Poland and Germany. The subspecies Cepphus grylle atlantis is observed irregularly on the North Sea coast of Belgium and the Netherlands and occasionally also on the Baltic Sea coast.

description

In adult animals, the body length is 32 to 38 cm and the wingspan is 49 to 58 cm. Adult birds in Iceland weigh an average of 427 grams, while breeding birds in Alaska weigh an average of 383 grams.

The plumage is predominantly brown-black in the splendid plumage and shows a green shimmer when freshly moulted. Sometimes a few white feathers of the resting robe remain on the chin, lower chest and stomach of some birds. The wings carry an oval, white field, which is formed by the outer large and middle arm covers. Under wing-coverts and axillary feathers are predominantly white. The beak is black with a red throat. Legs and feet are colored red. In the plain dress the bird is predominantly white. On the skull and neck, the plumage is brown to blackish-brown at the base and appears spotty due to the white tips. More or less dark feathering can also be found on the reins, ear covers and partly around the whole eye. The back is brown-black and looks banded by white hems. These are narrow on the front back and become wider towards the back. They are so wide on the rump that it appears completely white. On the otherwise white underside, dark feather bases can shine through on the throat, chest and flanks. The wings and tail are colored as in the magnificent dress.

In the youth dress, the top is dark slate gray and shows white feather hems on the shoulders. The white underside is darkly banded or speckled by gray hems. The black parts of the wing in adult birds are dark slate gray and there is a dark point on the white middle arm cover. The front part of the oval wing field appears dark gray rather than white. The first winter dress is still very similar to the youth dress. The crown and neck are lighter. Even in the first breeding plumage, the white wing field appears strongly spotted. The rockers and control springs often appear silver-gray when worn. Some birds are predominantly brown-black in their youthful clothes. This variant occurs more often in some subspecies than in others.

Spreading and migrations

The black guillemot is a breeding bird on the coasts of the North Pacific including the Bering Strait and Arctic North America, the Arctic archipelagos of Eurasia and northwestern Europe to the south of Ireland and Sweden. The occurrences in Europe are on Iceland , the Faroe Islands , Ireland , Norway on the island Runde and in Scotland as well as on smaller islands off the coast of England. In North America one meets the species from Maine northwards and in small numbers also in Alaska . In the Pacific, the breeding areas overlap with those of the pigeon duck .

The wintering takes place in ice-free sea areas, which are not very far from the breeding areas. The subspecies Cepphus grylle grylle , native to the Baltic Sea , is concentrated in the west and south of the Baltic Sea in winter. Usually the wintering areas are reached in December to January. The return to the breeding grounds takes place in April and May. The breeding birds of Great Britain and Ireland tend to stay close to their breeding colonies. The subspecies C. g. arcticus usually does not overwinter more than 300 to 400 kilometers from the breeding site. In winter it sometimes stays in drift ice, for example in the White Sea . The return to the breeding grounds also depends on the ice conditions.

food

Adult bird with Atlantic butterfish on Iceland

These birds start their foraging dives from the surface of the water. Before diving, they often stretch their heads up over their eyes into the water. They mainly prey on fish, but also crustaceans , molluscs and parts of plants. In addition to mollusks and bristle worms , crustaceans play an essential role in nutrition, especially in the winter months.

The food acquisition usually takes place in shallow waters near the coast. Black guillemots usually feed there in waters that are less than thirty meters deep. But they can also be seen far out on the edge of the pack ice and on icebergs. Breeding birds in Denmark and Shetlands rarely look for food more than two to three kilometers outside their breeding colonies. Breeding birds in Hudson Bay , on the other hand, regularly move up to five kilometers from the nesting site and can occasionally be observed at a distance of 13 kilometers. Black guillemots can dive up to fifty meters, but they mostly find their food in places that are less than thirty meters deep. The individual dives lasted an average of 73 seconds, with an average pause of 27.5 seconds between dives. The daily food requirement in captive birds is 80 to 240 grams of fish.

Reproduction

Black guillemots on Svalbard
Young birds a few days before leaving the breeding site in Iceland

The breeding grounds of the black guillemot are on rocky islands and cliffs. They are usually located directly on the coast on rock, gravel or sand islands or between rocks at the foot of steep embankments. Occasionally there are breeding sites up to 600 meters above the water level. In breeding colonies where several species of birds breed, they usually occupy the lower floors.

Eggs ( Museum Wiesbaden Collection )

They are cave breeders . Sometimes the guillemot even breeds in holes in harbor walls, on buildings and even in nesting boxes. Usually it is a single brooder, but occasionally it breeds in small colonies with up to 20 breeding pairs. The distribution of the breeding sites is mainly determined by the availability of suitable nesting sites. Only one clutch is raised per year. If the clutch is lost, there is a new clutch.

Black guillemots reach sexual maturity at the earliest two years. They lead a monogamous seasonal marriage, whereby they show a high loyalty to the breeding site and also a high loyalty to the partner. The eggs lie in the cave on a scratched hollow on the floor. The start of laying depends on the distribution area. The breeding season in the European distribution areas begins at the beginning of May at the earliest, in the more northern distribution areas usually not until June. The clutch usually consists of two eggs. These are short spindle-shaped or elongated oval. The basic color is white to greenish with large dark brown spots. The incubation period is 25 to 36 days. Both parent birds are involved in the brood, with the male usually breeding during the night and the female during the day. The young birds are also looked after and hoed by both parent birds. The young birds leave the nesting site at a time when their flight feathers are not yet fully grown, but these allow them to slide off slowly.

In studies in Denmark, 59 percent of the eggs hatched and 54 percent of these reached the age at which they left their nesting site. In Iceland, however, the hatching success was 80 percent and 89 percent of the young birds reached the age of egress. Ground robbers such as weasels and rats are a major cause of reduced breeding success. The average mortality rate of adult birds in Iceland is 13 percent. The oldest ringbird found again reached an age of 22 years and 11 months.

Existence and endangerment

The exact global population is not known, but it is estimated to be around 390,000 breeding pairs. Four of the five subspecies occur in Europe. The number of breeding pairs here was estimated at 130,000 to 300,000 breeding pairs at the beginning of the 21st century and is considered stable overall. Populations with more than 10,000 breeding pairs can be found on Greenland, Iceland, Norway, Svalbard, Finland, Great Britain and Russia, among others. While stocks are declining in Scandinavia, they are stable in Iceland, Greenland and the Faroe Islands, and are even increasing in Finland, Denmark and the UK. The breeding populations in south east Scotland are in the 19th century, those in Yorkshire in 1948.

As with other alkenes, oil pollution, human persecution, drowning in fishing nets, and climatic conditions are the main causes of mortality. The predators include the mink and rats.

Subspecies

Black guillemot on a buoy

Between three and seven subspecies are described, five of which are widely recognized. For the most part, these vary very gradually (clinically) with regard to the length of the extremities and the beak as well as the extent of the white plumage. The former features largely follow Allen's rule , the latter follow Gloger's rule .

  • Cepphus grylle grylle ( Linnäus , 1758) - Baltic Sea
  • Cepphus grylle mandtii , ( Lichtenstein , 1822) - northern Arctic, eastern North America, south to Labrador and northern Newfoundland, west and east Greenland, Jan Mayen and Spitzbergen, from there east through Siberia to northern Alaska
  • Cepphus grylle arcticus , ( CL Brehm , 1924) - subarctic in North America as well as from southern Greenland to the British Isles and Norway, southwestern Sweden, Denmark, Murmansk and the White Sea
  • Cepphus grylle faeroeensis , ( CL Brehm , 1931) - Faroe Islands
  • Cepphus grylle islandicus , Hørring 1937 - Iceland

supporting documents

literature

Web links

Wiktionary: Black guillemot  - explanations of meanings, word origins, synonyms, translations
Commons : Black guillemot  - album with pictures, videos and audio files

Single receipts

  1. ↑ Bauer et al., P. 570
  2. ↑ Gaston et al., P. 169
  3. ↑ Glutz v. Blotzheim, pp. 1062f, s. literature
  4. ↑ Gaston et al., P. 172
  5. ↑ Gaston et al., P. 173
  6. ↑ a b c d e Bauer et al., P. 571
  7. ↑ a b Bauer et al., P. 572
  8. ↑ Glutz v. Blotzheim, pp. 1059f, s. literature