Craverialk

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Craverialk
Alcidae - Synthliboramphus craveri.JPG

Craverialk ( Synthliboramphus craveri )

Systematics
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Alkenbirds (Alcidae)
Genre : Synthliboramphus
Type : Craverialk
Scientific name
Synthliboramphus craveri
( Salvadori , 1861)

The Craverialk ( Synthliboramphus craveri ) is a monotypical species from the family of alken birds . It is a small and so far little researched alkenbird, which like the Lummenalk has black and white plumage all year round. It occurs exclusively on the coasts of the North Pacific.

The IUCN classifies the Craverialk as endangered ( vulnerable ) due to its small distribution area and the small population .

Appearance

The Craverialk reaches a body length of 25 centimeters and weighs about 152 grams. Adult Craverialks have a black-brown neck and neck and head all year round. On the face, the black-brown color extends to the base of the beak. The trunk and tail are also black-brown. The lower chin, throat, chest and tail-coverts, on the other hand, are bright white. The beak is long, slender and tapers at the end. The beak color is black. The iris is dark brown. The feet and legs are light blue with darker webbed feet.

The wings are pointed and the body is slender. Fast flight close to the surface of the water is typical for Craverialken. On land, the Craverialk moves awkwardly due to its legs that are far back on its body. He is unable to stand erect on his feet, but usually crouches on the legs.

In contrast to adult craverial birds, juveniles have shorter wings and a shorter beak. The plumage looks deeper black; it still lacks the sheen that is typical of the plumage of adult birds.

Distribution area

The only proven breeding sites are on the coast of the Gulf of California , a 160,000 km² tributary sea to the Pacific between Mexico and the Baja California peninsula . Other breeding colonies may be found on the Pacific coast of Baja California. Outside the breeding season, the Craverialk can be found in subtropical waters off the west coast of Mexico and the south of the US state of California. It then occurs as far as the coast of Monterey , where it can be observed regularly from mid-July to mid-October. In November the birds return to their breeding grounds.

Way of life

Craverialks prefer to eat fish with a body length of four to seven centimeters. Their preferred food are juvenile fish of the genus Sebastes , herring and Benthosema panamense .

The breeding colonies are mainly found on islands with only sparse desert vegetation and little rainfall. Some of the islands have high numbers of snakes. However, mammals are absent from these islands. The nests are built in crevices and holes in the rocky coast. The eggs are laid in February and March. The clutch usually consists of two eggs. Clutches that have three eggs are believed to be the result of two female birds sharing a nest. The eggs have an elliptical to oval shape and are greenish-brown in color. They show a pattern of spots, but this is not as pronounced as in the Lummenalk . Nothing is known about the breeding season, but it is probably 31 days, similar to that of the Lummenalk. The young birds hatch in March and April. As with the Lummenalk, they leave the nest hole at one or two days of life and are raised by their parent birds on the high seas. The start of breeding is only slightly synchronized within a colony.

Duration

The population in the Gulf of California is estimated at 5,000 pairs. Together with the non-breeding birds, the total population is estimated at 15,000 to 20,000 individuals.

supporting documents

literature

  • Jonathan Alderfer (Ed.): National Geographic complete Birds of Northamerica. National Geographic, Washington DC 2006, ISBN 0-7922-4175-4 .
  • Anthony J. Gaston, Ian L. Jones: The Auks (= Bird Families of the World. Vol. 4 (recte 5)). Oxford University Press, Oxford et al. 1998, ISBN 0-19-854032-9 .

Single receipts

  1. ↑ BirdLife factsheet on the Craverialk , accessed on October 18, 2010
  2. ↑ Gaston et al., P. 211
  3. ↑ Alderfer, p. 288
  4. ↑ Gaston et al., P. 211
  5. ↑ BirdLife factsheet on the Craverialk , accessed on October 18, 2010
  6. ↑ BirdLife factsheet on the Craverialk , accessed on October 18, 2010
  7. ↑ Gaston et al., P. 212

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