Laysanalbatros

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Laysanalbatros
Laysanalbatros

Laysanalbatros

Systematics
Class : Birds (aves)
Order : Tubular noses (Procellariiformes)
Family : Albatrosses (Diomedeidae)
Genre : Phoebastria
Type : Laysanalbatros
Scientific name
Phoebastria immutabilis
( Rothschild , 1893)
Head of a laysanal batross

The Laysanalbatross ( Phoebastria immutabilis ) is a species of the albatross . Despite its wingspan of around two meters, it is the smallest species of North Pacific albatross. Due to its dark brown upper side of the body, which clearly stands out from the light underside of the body, it is easy to distinguish even when observing in the field. Like all albatrosses, he is an excellent glider. When there is no wind, it flies close above the water; when it is windy, it is characterized by a zigzag flight in which it alternately ascends and glides diagonally downwards. They are active day and night. During the day the albatross occasionally rests on the surface of the water. This behavior can be observed especially when there is no wind. It breeds in large breeding colonies, and mostly roams the seas one by one.

The Laysanalbatross is the second most common seabird on the Hawaiian Islands. Its name is derived from the northwestern Hawaiian island of Laysan . Outside of the breeding season, it roams an area in the north of the Pacific, as it stretches from the coasts of Japan and Alaska to the coastal regions of California.

In 2010 the IUCN upgraded the status of the Laysanalbatros from vulnerable to near threatened , as the populations of this species have increased again in recent years. The population is estimated at around 591,000 breeding pairs or 1.7 million individuals.

features

Laysanal anatrosses show no gender or seasonal dimorphism . The head, neck and underside of the body are white. The top of the wing and the back are dark brown. The tail has a dark end band. There is a dark spot in front of the eye. Adult Laysanal batrosses have a wing length between 47 and 50 centimeters, the beak measures between 11 and 13 centimeters. The legs are seven to nine inches long. They weigh between 1.8 and 3.7 kilograms.

Young birds are difficult to distinguish from adult birds. However, they are overlaid with gray on the neck, while adult birds are more yellowish on the neck. The beak is yellow in both juvenile and adult birds, with the tip and base of the beak being slightly darker. The legs are flesh to pink in color.

Distribution area

99% of the Laysan aquatic animal population breed in the Hawaiian Islands, primarily Laysan and the Midway Islands . With around 660,000 pairs, almost 40% of all black-footed alabies breed in this area. There are also breeding areas on the Bonin Islands , near Japan and off Mexico on Guadalupe and the Revillagigedo Islands . A total of 16 breeding colonies are counted today, nine of which contain more than 100 breeding pairs. On Torishima , where the very rare short-tailed albatross breeds, as well as on the island of Wake and the Johnston Atoll , Laysanal fish were exterminated by hunting at the beginning of the 20th century.

The area that Laysanal seaatrosses roam outside of the breeding season encompasses the entire North Pacific from the northern limit of the tropical zone. During the winter, Laysan Atlantic seabows are mainly seen in an area between Honshu, the Aleutian Islands and Hawaii. In the summer, on the other hand, it is rare in the Eastern Pacific, where the focus of its occurrence shifts to the northwest. Based on ringing data, it is concluded that young birds do not return to the breeding colonies during their first year of life. In the second year of life, part of this age population begins to return to the brood island, the return is more regular from the third year of life.

Black-footed and laysanal aatrosses are considered sympatric species, which creates interspecific competition and influences their oceanic distribution. Overall, the areas they roam are almost identical. However, their main areas of concentration differ, as the Laysanalbatross prefers to migrate to the Northwest Pacific and the Black-footed Albatross to the Northeast Pacific.

food

The Laysanalbatross lives mainly on cephalopods , but also eats crabs, fish and tunicates . He spies food objects through search flights over the water. If he sees food, he settles on the surface of the water.

Unlike the black-footed albatross, the Laysanalbatross rarely follows ships, so that waste thrown overboard plays a minor role in the Laysanalbatross' diet.

Reproduction

Laysanalbatrosses when courting; The front pair shows the "vertical neck extension", one of the typical courtship poses

The Laysanalbatross usually becomes sexually mature at the age of seven to ten years. In some individuals, however, sexual maturity can already be given at the age of five. The males tend to become sexually mature a year earlier than the females. They enter into a monogamous permanent marriage and show a pronounced local loyalty. The nest is not far from the previous year's nesting location. On average, the distance from the old nesting site is only 1.3 meters.

Not all sexually mature and mated birds actually brood. Only two thirds of reproductive albatrosses breed annually. It is usually the younger albatrosses that are exposed to a breeding season. Laysanal batrosses can breed even in old age, as the example of the female "Wisdom" shows, which was marked in 1956 and which still raises young today.

Return to the breeding colonies and courtship

Laysanal fish return to their breeding colonies in November. The main return time is the second ten days of November. The males appear in the breeding colony between six and sixteen days before the females and initially occupy their nesting territory. As soon as the breeding partner also appears at the nesting site, the courtship rituals begin, which in the case of breeding pairs end with the building of the nest. Non-breeding Laysanal Bats mate throughout the breeding season, gradually forming pair bonds.

During courtship the two partner birds face each other head-on. The courtship elements include beak contact, alternating wing lifts while simultaneously touching the beak of the wing, vertical neck extension with the birds standing on their toes and looking at the partner's chest.

The first copulation takes place within 24 hours after the female has also reached the nesting area. It leaves the breeding colony within about a day and a half, but then returns after 10 days and then lays the egg within 24 hours.

Clutch and rearing of young birds

The nest is a hollow in the sand or in the ground that is about five centimeters deep and about one meter wide. Laysanal batrosses create this hollow immediately before laying their eggs. During the incubation of the egg, this nest is supplemented by twigs and grasses by the brooding bird, which does not rise from the nesting trough.

The eggs are laid from mid-November to mid-December. Laysanal batrosses lay a single egg. There are nests with two eggs, but the eggs then come from two different females. The egg weighs between 218 and 317 grams, which is an average of 12 percent of the female's body mass. The egg has an elongated-ellipsoidal shape. The shell is pure white.

Both parent birds are involved in the brood and, as a rule, detach five times, more rarely seven or eight times, during the 65-day brood. The chick hatches between the third decade of January and the second decade of February. For the first few weeks thereafter, the parents take turns returning to the chick every day to feed it. The young bird is fed stomach oil and pre-digested food. Towards the end of the nestling period, each parent bird feeds three to four days apart. In total, each of the parent birds performs between 60 and 70 foraging flights. Only both parent birds together are able to feed a young bird until it flies. The death of one of the two parent birds leads to the death of the boy.

The young bird fledged after around 165 days. They fly out between the end of June and the beginning of August. Most young birds leave their nest in July.

Duration

During the courtship

Although the laysanalbatross is still common, it was hunted for its feathers and killed by the hundreds of thousands in the early 20th century. That's why he disappeared from Wake Island and Johnston Atoll . Negative on stocks also appeared driftnets from which 1,978 to 1,992 deep-sea fishing was operated. Even if the population has increased in recent years, the current population is below those before the Laysanalbatross was hunted so intensively. The IUCN assesses the current population as stable.

The bird is at risk from longline fishing and from plastic that it swallows. The IUCN estimates that between 5,000 and 18,000 Laysanal fish are killed by longlines annually. In the breeding colony on Guadalupe , domestic cats have also proven to be an essential predator of adult Laysanal aatrosses and their young birds.

Since 2015, breeding birds on the Midway Islands have been increasingly attacked by house mice. The rodents climb over the backs of the albatrosses and start parasitically attacking the birds. The birds can only defend themselves to a limited extent as they cannot reach the rodents with their wings and do not want to leave their breeding grounds under any circumstances. Sometimes the albatrosses are so badly injured that they perish. A definitive cause for this mutated behavior has not yet been clarified. It is possible that the 2015 drought in the Midway Islands caused house mice to behave in this way in their search for fluid.

All large breeding colonies on the Hawaiian Islands are now in the area of ​​the Papahānaumokuākea Marine National Monument and are therefore under special protection. Fishing with longlines is prohibited near this nature reserve.

In 2010, the inventory was 1,180,000 copies.

supporting documents

literature

  • VD Il'ičev & VE Flint (eds.): Handbook of birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . Aula Verlag, Wiesbaden 1985, ISBN 3-89104-414-3
  • J. McQuilken & R. Stange (eds.): The mists of time. Spitzbergen.de-Verlag, 2012.

Web links

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

Single receipts

  1. ^ IUCN website on Laysanalbatros, accessed June 28, 2013
  2. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 292
  3. ^ IUCN website on Laysanalbatros, accessed June 28, 2013
  4. ^ IUCN website on Laysanalbatros, accessed June 28, 2013
  5. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 293
  6. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 293
  7. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 295
  8. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 293
  9. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 293
  10. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 293
  11. ^ IUCN website on Laysanalbatros, accessed June 28, 2013
  12. ↑ 66-year-old female according to SPIEGEL on December 10, 2016
  13. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 294.
  14. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 294.
  15. ↑ Il'ičev & Flint: Handbook of Birds of the Soviet Union - Volume 1: History of exploration, Gaviiformes, Podicipediformes, Procellariiformes . 1985, p. 294.
  16. ^ IUCN website on Laysanalbatros, accessed June 28, 2013
  17. ^ IUCN website on Laysanalbatros, accessed June 28, 2013
  18. ↑ COLONIES IN DANGER - Mice eat albatrosses >
  19. ↑ James McQuilken: The Mists of Time . Ed .: Rolf Stange. 1st edition. Spitzbergen.de, 2012, ISBN 978-3-937903-15-6 , pp. 137 .