Red-beaked lalk
| Red-beaked lalk | ||||||||||
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Red-billed lalk ( Aethia psittacula ) |
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| Scientific name | ||||||||||
| Aethia psittacula | ||||||||||
| ( Pallas , 1769) |
The red-billed lalk ( Aethia psittacula , the previous classification Cyclorrhynchus psittacula is no longer in use) is a small, monotypical sea bird of the northern Pacific , which belongs to the family of the alkenvirds . It breeds on islands that are far off the coast of Alaska or Kamchatka . The IUCN currently rates the species as harmless.
Appearance
The red-billed lalk reaches a body length of 25 centimeters. Males tend to be a little heavier and weigh an average of 292 grams, while the females weigh 266 grams. It is a strongly built alken bird with an unusually short and very strong, red beak that looks almost round in profile. The tongue is conspicuously pink, which is clearly visible in calling birds. The iris is strikingly white. The neck is relatively long, the wings are rounded and the feet are unusually large in relation to their height. The posture is upright on land. Red-billed alks move with a comparatively great dexterity for an alkenbird. They are persistent fliers.
The red-billed lalk has predominantly black to black-gray plumage in its splendid plumage. Only the lower half of the chest and the belly and a line extending from the eye are white. In swimming red-billed falcons, only the dark upper side of the body is visible. In the plain dress , the throat and chin are also white, the white eye line is less pronounced.
Fledglings resemble adult birds in simple dress, but have smaller and above all dark-colored beaks. Two-year-old birds that are not yet sexually mature have small, white spots on their throats.
On land, the red-billed lalk should not be confused with any other alkenbird because of its posture, the white stripe behind the eye and the strong, short, red beak. On the high seas, however, there is a possibility of confusion with the dwarf , bearded , crested , Aleutian and rhinoceros lalk .
voice
Similar to the Aleutian alek , the red-billed lalk is a very call-happy species. Both pairs and single males call out when they are near their nesting burrows. Calling birds put their heads up. During the courtship, the couples also call together.
Distribution area
The red-billed lalk is a breeding bird in the North Pacific. He prefers to stay in waters that have a surface temperature of two to fifteen degrees Celsius in summer and a surface temperature of two to eight degrees Celsius in winter. Basically, the red-billed lalk spends more time on the open sea than the rhinoceros and other species of the genus Aethia .
In Asia, its breeding area extends from the Kuriles and the Sea of Okhotsk to the commanders' islands and, in isolated cases, to the coast of the Kamchatka Peninsula and the Chukchi Peninsula . On the North American coast, the red-billed lalk breeds in the north of the Gulf of Alaska , including on the Shumagin Islands , the Semidi Islands , the Tschirikow Island and the Aleutian Islands and on islands of the Bering Strait . The northernmost breeding colony is found on 29 square kilometers of Ratmanov Island , the easternmost point of Russia . The most southeastern breeding colony is probably on an island off the coast of Sitka in southeastern Alaska, and the southwesternmost near Sakhalin in the Sea of Okhotsk.
During the winter months, red-billed falcons can be found sporadically in the coastal waters of British Columbia, Washington, Oregon and California. A stray visitor even found himself on a lake in Sweden.
food
The red-billed lalk eats a wide variety of small zooplankton creatures . Small jellyfish and plankton, which is associated with jellyfish, play a special role in its diet. Its specific beak shape is attributed to this food preference. They find their food mainly on the surface of the water and their food consists mainly of animals that do not show any escape behavior. Studies on diving behavior of this type are so far lacking, but it is not likely that red-billed eagles are extremely good and fast divers.
Reproduction
Breeding colony and couple relationship
The presence of the red-billed falcon in the breeding colonies is less synchronized than is the case with other Aethia species. The density of nest holes in the breeding colony is also lower. Where they use the same breeding colonies as other Aethia species, they rarely take part in the overflights over the colonies, as is characteristic of the other species of their genus. Usually, small groups of ten to forty red-billed falcons gather in the coastal waters in front of the breeding colonies in the early hours of the morning and fly from there individually or in pairs to the breeding caves. The activities in the breeding colony are also relatively little aligned. Aggressive behavior towards other conspecifics is relatively rare, which clearly distinguishes them from the dwarf and crested lalk.
Red-beaked falcons are sexually mature at the age of three or four years and marry in a monogamous season. Pairings outside of the couple relationship do occur, but are relatively rare. Newly mated pairs copulate about 1.5 times an hour. The copulations take place exclusively on the high seas, they are followed by an intense beaking and calling together.
nest
Red-beaked falcons are not very specialized in their nesting locations compared to other North Pacific alkenbirds. On islands lacking mammals that are predators of the red-beaked falcon, red-billed falcon breed in crevices between rocks on the coast and on cliffs. They also use gently sloping hills to dig nest holes in. Their ability to dig themselves burrows is believed to be the reason for their unusually large feet. On islands such as the Pribilof Islands , where foxes live, their nesting sites are limited to inaccessible cliffs. The distance between individual red-billed falcon nests is usually several hundred meters. In breeding colonies they are occasionally associated with dwarf galaxies and crested hawks. But even here they avoid the immediate vicinity of nests of this type.
Eggs and young birds
The time of oviposition falls in the western Aleutian Islands in the period from late May to mid-June. On the Pribilof Islands, which are a little further north, the egg-laying period falls in the first half of June. Basically, in the northern colonies, the time when the snow melts affects the start of the breeding season. The clutch consists of only one egg. This is elliptical and has a smooth shell surface. The egg shell is whitish and occasionally has a bluish or greenish tinge. It is characteristic that the eggs become increasingly dirty during the breeding season due to the dirt in the breeding cavity. Freshly laid eggs have an average weight of 37.6 grams, which is 14 percent of the body mass of an adult red-beaked lalk. Both parent birds are involved in the incubation of the egg. They form two parallel breeding spots that are covered with feathers again very quickly after the young bird hatches. The breeding season averages 35.2 days. The female and male parent birds usually alternate with incubation at an interval of 24 hours.
At the time of hatching, the young bird weighs around 20 grams. On the first day after hatching, it is fidgeted continuously, after which it gradually decreases during the day until the parent birds leave the young bird, about a week old, alone during the day. The parent birds bring food several times a day. The nestling period is an average of 26 days. Young birds fly into the open sea without the accompaniment of their parent birds. There is no evidence that the parent birds continue to look after the young bird after they have fledged.
Breeding success and life expectancy
It is estimated that for every 100 breeding pairs of red-billed falcons, around 50 young birds fledge. The predators include arctic fox and red fox, which mainly beat adult birds, as well as voles , which eat eggs and young birds. Red- beaked falcons are also struck by Kamchatka gulls , Bering gulls , bald eagles , giant sea eagles , gyrfalcons and peregrine falcons .
Life expectancy is not very well studied. On an island in the Sea of Okhotsk, where this species was studied a little more intensively, 93 percent of the marked red-beaked falcon returned to breeding in the next year.
Duration
With an estimated population of over a million individuals, this species is not considered threatened. An exact inventory is lacking, especially since the birds that breed on the Asian coasts have never been counted. The number of breeding birds in the Sea of Okhotsk is estimated at 300,000. In the Aleutian Islands, the population has declined sharply since arctic foxes were introduced there to promote the fur trade. Like many other alkenbirds, the population is probably also influenced by the oil pollution in the sea, but the exact influence has not yet been investigated. The red-billed lalk is particularly sensitive to small plastic particles floating in the sea. 94 percent of the red rots shot on the high seas had such plastic in their goiters. The influence on the health of the birds has not yet been conclusively investigated.
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
- ↑ Rotschnabelalk on Avibase , accessed on October 22, 2010
- ↑ BirdLife factsheet on the red-billed lalk , accessed on October 23, 2010
- ↑ Gaston et al., P. 236
- ↑ Gaston et al., P. 238
- ↑ Gaston et al., P. 239
- ↑ Gaston et al., P. 236
- ↑ Gaston et al., P. 236
- ↑ Gaston et al., P. 238
- ↑ Gaston et al., P. 239
- ↑ Gaston et al., P. 240
- ↑ Gaston et al., P. 240
- ↑ Gaston et al., P. 240
- ↑ Gaston et al., P. 241
- ↑ Gaston et al., P. 241
- ↑ Gaston et al., P. 241
- ↑ Gaston et al., P. 241
- ↑ Gaston et al., P. 242
- ↑ Gaston et al., P. 238
Web links
- Aethia psittacula inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved November 23, 2013.