Hornlund

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Hornlund
Hornlund (Fratercula corniculata)

Hornlund ( Fratercula corniculata )

Systematics
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Alkenbirds (Alcidae)
Genre : Lunde ( Fratercula )
Type : Hornlund
Scientific name
Fratercula corniculata
( Naumann , 1821)
A pair of horns

The Hornlund ( Fratercula corniculata ) is a species from the family of alken birds . The Horned Puffin is similar to the spread in the Atlantic Puffin , a strongly built, medium-sized Auk with a massive but slender beak. Unlike the puffin, the hornlund has a yellow beak with a red tip during the breeding season. It is a northern Pacific marine bird that scuba dive for fish. No subspecies are described for this species.

The population situation of the Hornlund was classified in the IUCN Red List of Threatened Species in 2016 as “ Least Concern (LC) ” = “not endangered”.

Appearance

general characteristics

The Hornlund reaches a body length of 38 centimeters. Sex dimorphism is not very pronounced, but males tend to have slightly longer legs and wings. Males weigh between 531 and 754 grams and females between 499 and 691 grams. The beak is significantly larger than that of the puffin. Legs, toes and webbed feet are bright orange. The flight is straight, with fast, flat wing beats. Similar to the puffin, the Hornlund has an upright posture on land. He just stands on his toes. On land, the Hornlund is very agile, it runs in a forward-leaning posture.

Splendid and simple dress

In the splendid dress , the back, the wing-coverts and the tail are black. The crown and neck are grayish, the underside of the body is white, but the throat and chin are black. A thin, reddish eye ring runs around the dark eye and around it is a dark, featherless skin flap that tapers like a horn to the top of the head. Another dark line runs from the end of the eye to the nape of the neck. This eponymous facial drawing is particularly noticeable in the magnificent dress when the face mask is bright white. The beak is yellow with a red tip.

In the plain dress , the beak is darker and smaller. The tip of the beak is still red. The eye ring is then brown, the legs pale flesh-colored. The face mask is gray-brown and lightens to a silver-gray behind the eye. Fledglings resemble adults in simple dress, but have a shorter and consistently brown beak. Her cheeks are soot-colored. Young, not yet sexually mature birds differ in their splendor from the breeding birds by a less pronounced beak.

Possible confusion

There is usually no possibility of confusion with other alken birds . Only in the flight of the Horned Puffin can from a distance with the rhinoceros auklet or Lummen be confused. But even from a distance, the significantly larger beak compared to guillemots is noticeable. The Hornlund also has more rounded wings and a slower wing beat. Compared to the rhinoceros balk, the black and white contrast of the plumage is more pronounced. The rhinoceros beak also has a pointed beak.

distribution

Distribution area of ​​the Hornlund
Hornlunde off Alaska

The Hornlund is a widespread species in the North Pacific. On the coast of North America, it breeds from British Columbia to southeast Alaska, Kodiak, Semidi and Shumagin, the Alaska Peninsulas and the Aleutian Islands to Rat Island . Breeding colonies are located on the Pribilof Islands , St. Matthew Island , Hall Island , St. Lawrence Island and along the coast of the Seward Peninsula, as well as Cape Thompson and Cape Lisburne, both of which are part of Alaska. Hornlunde also breed on Wrangel Island and the Chukchi Peninsula . They also colonize the entire Russian coast of the Bering Sea up to the Kronotsky Nature Reserve , the Commander Islands and the Kuril Islands. They are also found on the north coast of the Sea of Okhotsk and on parts of Sakhalin .

Like other Lunde, Hornlunde overwinter far from the coast and are then widespread in the North Pacific. Some Hornlunde remain in the region of their breeding grounds unless the sea ice forces them to migrate south. During the winter months they can often be seen near the Kuril Islands, Sakhalin, Kamchatka and the Commander Islands. Individual birds are also seen off the coast of British Columbia and Japan as far as Honshū . Hornlunde can also be seen as far as California and Baja California.

Food and diet

Hornlunde are pelagic seabirds that stay far away from the coast, with the exception of the breeding season. Only during the breeding season do they look for food near their breeding colonies. The diet of adult hornbills has not yet been adequately researched, but it appears that they eat fish, squid and invertebrates during the summer months. Young birds, on the other hand, are fed almost exclusively with fish by their parent birds. The composition varies depending on the area of ​​distribution, but among the food fish are typically sand eels and capelans .

Reproduction

Like most seabirds, hornlunds are colony breeders. Breeding pairs defend their nest cavity and the male defends his partner. Aggressive behavior includes a threatening posture in which the body is almost horizontal to the floor, the neck is stretched wide and the head is lowered. Aggressive acts include persecuting one another, grasping the beak or feathers on the head or neck. Mating takes place almost exclusively in the water.

Compared to other alken birds, the reproductive behavior has been relatively little studied. They return to the colonies on the Kuril Islands in April. On the St. Lawrence Island, however, only at the beginning of June. They breed on cliffs and occasionally on scree slopes . The nesting distance is relatively large. On the island of Talan in the Sea of ​​Okhotsk, the minimum distance was at least 1.5 meters. Although some colonies are very large, a large number of Hornlunde breed in colonies that contain fewer than 1,000 breeding pairs. The nest is in a crevice or under boulders. Occasionally Hornlunde also dig nests. The actual nest is laid out with grass and some feathers. In the Gulf of Alaska, eggs are laid mostly between June 14th and 26th. On the other hand, on St. Lawrence Island, the peak of oviposition falls between June 20 and 28.

The clutch contains only one egg. It is elliptical to oval and has an occasional rough surface. The base color is whitish with pale brownish or lavender spots. Eggs weigh an average of 75.3 grams, which is about twelve percent of the body mass of an adult Hornlund. The egg is incubated by both parent birds for an average of 41.1 days. Both parent birds have brood spots. The chick has a hatching weight of 58.6 grams and is huddled for up to six days and fed between three and six times during the day. The parent birds each bring an average of 13.7 grams of food. The chick gains up to 12 grams a day. They fledge with an average of 42.3 days. The young birds leave the breeding cave without the help of the parent birds. There is no indication that the young birds are still being looked after by the parent birds after they have fled.

Duration

Hornlunde

The population is estimated at 1.2 million breeding birds. About 62 percent of the world's population breed on islands off the Alaska Peninsula. Another eight percent breed in the Aleutian Islands and on islands in the Bering Sea. About 16 percent of the global population breed in the Sea of ​​Okhotsk. The largest Asian colony is on the island of Talan in the Sea of ​​Okhotsk, where about 100,000 to 120,000 breeding birds are found. About 17 breeding colonies off the Alaska coast have more than 10,000 breeding birds. The largest collection with around 350,000 breeding birds is located on the Semidi Islands , a chain of islands that lies roughly in the middle between the Alaska Peninsula and the Tschirikow Island . Suklik Island alone , which belongs to this group of islands, has more than 250,000 breeding birds.

Internal system

While there are considerable differences in body size in the puffin, the Atlantic sister species of the Hornlund, which correlate positively with the water temperature, such a differentiation is absent in the Hornlund, although this would be expected in view of its large distribution area. The ornithologists Anthony Gaston and Ian Jones therefore interpret this lack of a size difference as an indication that the Hornlund only settled large parts of its current range after the Pleistocene.

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 u. a. 1998, ISBN 0-19-854032-9 .

Single receipts

  1. Fratercula corniculata in the Endangered Red List species the IUCN 2016 Posted by: BirdLife International, 2016. Retrieved on October 10, 2017th
  2. BirdLife Factsheet on Hornlund , accessed November 4, 2010
  3. a b Gaston et al., P. 294
  4. Gaston et al., P. 293
  5. Alderfer, p. 294
  6. a b c Gaston et al., P. 296
  7. Gaston et al., P. 294 and p. 295
  8. a b c Gaston et al., P. 297
  9. Gaston et al., P. 197
  10. Gaston et al., P. 298

Web links

Commons : Hornlund  - album with pictures, videos and audio files