Alkenbirds

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Alkenbirds
Atlantic Puffin (Fratercula arctica)

Atlantic Puffin ( Fratercula arctica )

Systematics
Superclass : Jaw mouths (Gnathostomata)
Row : Land vertebrates (Tetrapoda)
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Alkenbirds
Scientific name
Alcidae
Leach , 1820

Alkenvögel (Alcidae) are a family of the bird order plover-like that occur exclusively in the northern hemisphere. They are thrush to duck-sized sea diving birds (the extinct giant aalk even reached about the size of a goose) with legs set far back, so that they show a more or less upright posture on land. Their morphological appearance is similar to that of the penguins , which occur almost exclusively in the southern hemisphere. The members of both families are black and white and stand upright. Both have short and close-fitting plumage and in both families the wings are reshaped for locomotion under water. Unlike penguins, most alken birds have retained their ability to fly. The only flightless species from this family, the giant aalk, became extinct in historical times. However, the similarity is based solely on convergent evolution . The two families are not closely related.

Alkenbirds live in the cool, boreal to cold, arctic waters of the North Atlantic and North Pacific. They usually breed on cliffs on the mainland or on remote islands. There they often form large colonies with other sea ​​birds . In the North Atlantic, for example, they share their colonies with the fulmar , northern gannet , shag , kittiwake and petrel .

anatomy

Alkenbirds are characterized by dense, black and white plumage and an upright posture on land. With the exception of the extinct giant alks , the recent species are all capable of flight, but have greatly shortened arm and especially hand wings. Due to their short and narrow wings, they have a high flapping frequency when flying. However, the wings are also used well when diving.

The plumage is very short and close fitting. Black-gray down covers the whole body and is used for thermal insulation. Similar to the penguins, the feather density is very high. With twelve feathers per square centimeter, it is twice as high as that of seagulls, for example .

All flight feathers are renewed at the same time, so the birds are temporarily unable to fly when they are moulting. The winter plumage often deviates considerably from the breeding plumage.

Reproduction

Alkenbirds only stay on land for a long time to breed. During the breeding season, most of them live in huge colonies on steep rocky coasts, on rocky outcrops and rock slopes. The clutch usually consists of only one egg. Only those species whose feeding grounds are close to their breeding grounds are able to procure enough food to raise two nestlings. The clutches of black-tailed , spectacled and pigeon ducks , all three of which belong to the genus Cepphus , usually consist of two eggs. The Lummenalk , which belongs to the genus Synthliboramphus , not only lays two eggs like all alks of its genus, but is also able to lay another clutch when the clutch is lost. However, the Aleutian alk is the only alken bird that occasionally manages to raise two clutches per year. The young birds of the Synthliboramphus species only remain in the nesting cavity for a day or two and then leave the breeding colony together with their parent birds. They are raised on the high seas. Guillemots raised in captivity experience a significant change in behavior 48 hours after hatching. While they remain calm in their nest until about this point, they then show very agile behavior and run around excitedly in their nesting boxes. At this point in time in the wild, their parent birds take them out to sea. By then you are already very good swimmers and able to climb over obstacles on land. Their further development on the high seas has not yet been documented. Guillemot birds reared in captivity showed only very slow weight gain and a change in their plumage only on the 17th day of life.

Thick-billed mummies

The three recent species of the genus Brachyramphus show an unusual breeding behavior for alkenbirds . The short-beaked lalk belonging to this genus breeds deep inland and regularly chooses stony slopes above the tree line as a nesting site. The only tree-breeding species among the alken birds also belong to this genus. Like their sister species, Kamchatka marmelalk and marmelalk occasionally breed very deep inland and build their nests on strong branches of old trees. The breeding behavior of the jellyfish, which in North America became a symbol of efforts to preserve pristine forests on the coasts of the United States, has been particularly well studied. The breeding area of ​​this species is usually 16.8 kilometers from the coast on average. Extreme nesting sites are up to 40 kilometers away. The typical nesting site is found on old trees that are at least 200 years old. Typical of the forests in which jellyfish nest is a small undergrowth under the tall trees, but a pronounced growth of moss and epiphytes. The top of the trees is 64 meters on average; the size of the forests in which jellyfish breed is on average 206 hectares. The nest is located in the upper area of ​​the nest tree about one meter away from the tree trunk on a strong branch that offers a nesting platform of about twenty by thirty centimeters. The nest is padded with lichen and moss and is usually not visible from above due to the branches hanging over it. Ground-breeding jellyfish have also been observed in Alaska. Brooding Marmelaken each have two lateral brood spots . The nestlings hatch after a breeding period of 27 to 30 days. Immediately after hatching, the nestling is fledged continuously for two days . The parent birds feed the nestling small fish, which they usually carry individually across their beak. The nestling period is 27 to 30 days, then the young bird usually flies to the sea alone, unaccompanied by the parent birds. It is not yet known how the young birds find their way to the sea. Some juveniles can see the sea shortly after taking off, but others have to travel long distances before sighting the sea. Young birds may remember the flight direction of the parent birds and use it as a guide.

evolution

The earliest alkenbird fossils date from the Miocene 15 million years ago. Some zoologists include older fossils from the Eocene in this family. Most and oldest finds come from the northern Pacific . However, in the US state of North Carolina , which lies on the Atlantic coast, fossils of about twelve different species of alkene were found in layers of the Upper Miocene and Lower Pliocene, so that a complex alkene community already existed at this time. Since only four endemic species are found in the Atlantic today, while there are sixteen endemic species in the Pacific, the predominant research opinion is that alkenbirds originated in the Pacific and spread from there. This is also supported by the fact that guillemots and thick-billed muzzles overlap in both oceans. A further indication of this thesis is that of the three recent species, Fratercula, one species, namely the puffin , occurs in the Atlantic and two others, namely the hornlund and the yellow-capped lump, occur in the Pacific.

Unlike other seabirds, the genera only contain a few species. This is certainly due to the small size of this family. Today, as in the past, the alkenbirds live in the cooler seas of the northern hemisphere. In warmer seas, the fish, which are the main food of the alkenbirds alongside krill , reach a speed that prevents successful hunting. The southernmost species in this family survive only because of the cold layers of water that rise off California and Mexico .

Duration

Crested falcon with oil-soiled plumage

As is the case with many seabirds, it is difficult to keep track of the alkenbird population. As a rule, seabirds are counted on certain sample areas and an estimate for the entire colony site is extrapolated from these results. However, this method only works to a limited extent with alken birds, as the number of birds present in a breeding colony can vary greatly with the time of day and season as well as with the weather or the tide. There are even bigger problems with determining long-term inventory trends, because historical sources provide fragmentary data at best. Basically, however, it is assumed that most species were much more numerous in the 17th and 18th centuries and that from the 19th to the middle of the 20th century, increasing persecution by humans led to significant population decreases.

The short-billed lalk is considered to be the most endangered species of the alkenbird. It only occurs in large numbers in a few, widely spaced places. The most famous are Glacier Bay National Park and Prince William Sound . The population of short-billed falcons is probably only between 20,000 and 50,000 individuals. 70 percent occur in Alaska. The IUCN classifies the species as critically endangered because populations have declined by 80 to 90 percent, especially in the last 15 years. Above all, the loss of breeding areas due to melting glaciers and marine pollution from ships and oil production facilities have a negative impact. The Exxon Valdez may have killed up to 10 percent of the world's population.

In the meantime, however, this information has been seriously questioned scientifically and the Kurzschnablealk was downgraded by the IUCN in 2014 to the considerably lower category "near threatened".

Hunting of alken birds

Pre-industrial use

Although alkenbirds live in relatively remote regions, humans have long used various species of this family as a source of food and raw materials for clothing. Remains of giant alks have been found in 40 Norwegian Køkkenmøddinger and similar finds exist for excavations in Newfoundland which date back to 4,000 BC. To be dated. Traces of Eskimo settlements can be found near all of the large beak-billed lumbar colonies in the eastern Canadian Arctic. On the Strait of Georgia , a waterway in the Pacific Ocean, there are Køkkenmøddinger, which contain among other things the remains of puffins and guillemots .

Use as food

Razorbill
Thick beaked mum

A number of different techniques have been used to hunt alken birds. One of the most common methods, found among Eskimo peoples of the Bering Strait, as well as Icelanders, Faroe Islands, and the Inuit of northwest Greenland, was to use a net attached to a long pole. The hunters hid behind stones or ledges and suddenly pushed these nets into the trajectory of the alkenbirds, which returned to the breeding colonies flying low. In the Qikiqtaaluk region , long sticks were used to kill the birds flying by. In Iceland, snare traps have been placed on small rafts anchored in shallow coastal waters to catch guillemots, puffins and razorbills. Techniques that were primarily used to capture flying alken birds were more sustainable, as they were primarily used to catch non-breeding birds. Typical for non-breeders is repeated circling over the breeding colonies, which means that they were hunted disproportionately often. The use of snare traps also led to the catching of mating, not yet breeding birds. It is estimated that 150,000 to 200,000 puffins have been caught using these methods annually in Iceland without causing a negative population trend. On the other hand, the shooting of breeding birds in colonies, which became common practice in Greenland during the 20th century, led to a drastic decline in the populations of thick-billed lemurs .

The eggs of the alkenbird are high in fat and have larger yolks than those of most other terrestrial bird species. Humans therefore traditionally collected eggs from alkenbirds and thus may have contributed to the fact that alkenbirds remained relatively rare on islands near to the coast and near human settlements. Collecting puffin and guillemot eggs was common in St. Kilda , Scotland , and excavations show this practice in Haida Gwaii , Canada, and islands in Alaska. Most of the indigenous peoples in the regions where alken birds were breeding developed techniques to preserve the meat and eggs for the time the alken birds were at sea. Samuell Prickett, one of the few who survived Henry Hudson's voyage of exploration in the bay named after him, described how the indigenous peoples of this region hung alken birds in stone huts, where the meat was preserved by air drying. Similar methods can be found in the Outer Hebrides . In the Qaanaaq region of Greenland, the preservation of the hunted crab grebes was even more important, as their meat was the only source of food in the autumn until the sea ​​ice was frozen enough to allow seal hunting again. The birds were sewn into seal skins, buried in the ground and later eaten raw. The Canadian researcher Fred Bruemmer , who was able to taste preserved meat using this method in 1950, compared the taste with that of very mature cheese.

Use as a resource for clothing

The skins of alkenbirds were particularly important for the indigenous peoples of North America, in whose region caribou was not found. Both the indigenous peoples of the Gulf of St. Lawrence and those of the Aleutians processed the skins of crested falcons and hornlunds into parkas. In other regions, the skins of parrot and crab divers were made into clothing that was worn under fur parkas. The spectacular beaks of the Fratercula species were used in many regions as decorations for ceremonial robes.

19th and 20th centuries

Hornlund

There is no evidence that the egg-collecting and hunting activities of pre-industrial peoples, who used the seabird colonies exclusively for subsistence purposes, led to sustainable population declines. The situation is different with commercial use, which began in the course of the 19th century and in which firearms played an essential role. The large alken bird colonies on the Gulf of St. Lawrence , which were described by John James Audubon in 1835 , had largely disappeared by the end of the 19th century. The giant alk was mainly hunted for its feathers and therefore died out in the first half of the 19th century. In the booming city of San Francisco due to the California gold rush , guillemot eggs were such a valuable commodity that the competition between egg collectors even led to exchanges of fire in 1863.

Large groups of alken birds attracted arctic foxes, which led, for example, to the fact that the indigenous peoples of the Qikiqtaaluk region, which is rich in alken birds, had a disproportionate share in Greenlandic fur exports in the 1940s. Arctic foxes were therefore introduced to the Aleutian Islands, which were also rich in alken birds and where there were no predatory mammals up to that point. While the crab divers in Greenland had a behavior adapted to predation by predation mammals, the alken birds found there lacked such behavior. The alken birds found there died out due to the stalking by the arctic fox.

Alkenbirds are still hunted today. Traditional hunts for guillemots and puffins still exist in Iceland and the Faroe Islands, albeit not as much as in earlier years. In the Canadian Arctic, the indigenous peoples there still have the right to hunt and collect their eggs. The egg harvest, however, accounts for less than one percent of the eggs laid by the birds that breed there. Guillemots are also hunted on Newfoundland and Labrador.

Research history

In 1758, Carl von Linné knew six species from the cauliflower family: the puffin, razorbill, giant aalk, black guillemot, thick-billed mum and crab grebe. The first scientific description of the guillemot was in 1763 by the Danish theologian Erik Pontoppidan . In his 1769 Spicilegia Zoologica, Peter Simon Pallas described the crested and red-beaked lalk and the yellow-cupped leek. Johann Friedrich Gmelin took in 1789 next to Ancient Murrelet and Marbled Murrelet and the whiskered auklet in the introduced Linnaeus binomial nomenclature on. By the end of the 18th century, 13 of the 23 alcvogel species recognized today were described.

Yellow cup

In his Zoographia Rosso-Asiatica, published posthumously in 1811, Peter Simon Pallas described five other species collected by Georg Wilhelm Steller , and in 1828 Nicholas Aylward Vigors named the short-beaked alk. The last alcvogel species were described until 1865. The taxonomic classification of species has been revised many times since 1758. Carl von Linné initially assigned all known species to the genus Alca , but Mathurin-Jacques Brisson introduced the genus Fratercula as early as 1760 . Until the end of the 18th century, individual species of alken birds were assigned to four other genera that are still valid today: Uria ( Morten Thrane Brünnich , 1764), Cepphus (Simon Peter Pallas, 1769), Aethia ( Blasius Merrem , 1788) and Pinguinus ( Pierre Joseph Bonnaterre , 1791). Heinrich Friedrich Link led in 1806 the genre all one, Charles Lucien Bonaparte named 1828 genus Cerorhinca and Johann Jakob Kaup in 1829 the species is no longer used today Cyclorhynchus . In 1837, the German naturalist Johann Friedrich von Brandt introduced the three genera Brachyramphus , Synthliboramphus and Ptychoramphus . The classification of genus and tribes proposed by Johann Friedrich Brandt in 1869 already largely corresponds to today's understanding; together with Samuel Elliott Coues , he is considered the founder of alkenbird research. In the second half of the 19th century it became increasingly clear that the similarity between alkenbirds and penguins was purely superficial and that this family was closely related to gulls and snipe birds . The 20th century was characterized by an increasing focus on researching the behavior and ecological role of the alkenbirds. The Life Histories of North American Diving Birds published by Arthur Cleveland Bents in 1919 described the findings on the behavior of Pacific alkenbirds, and the Handbook of British Birds published by Henry Witherby in 1941, among others , went into detail on the behavior of Atlantic alkenbirds. Starting in the 1930s, an increasing number of naturalists such as Ronald Lockley spent extended periods of time on islands with large breeding colonies to study the birds there, and a series of expeditions to Arctic and subarctic islands brought new knowledge about the species that breed in the Arctic. The Dane Finn Salomonsen began ringing alkenbirds on Greenland shortly after the end of the Second World War , a program that continued into the 1980s and provided important insights into the migration of alchebirds. Since then, a number of very detailed studies of alken birds have appeared. Many studies were often prompted by specific questions: In North America, the approval process for offshore oil production was the reason for a series of research contracts to determine the effects of the offshore drilling platforms on the alkenbird populations. Numerous studies in the 1980s focused on the ecosystems in which the alkenbirds lived in order to understand, among other things, the effects of commercial fishing on the populations of alkenes and other seabirds. Efforts to preserve the ancient coastal mammoth forests on the Pacific coast of the United States led in the 1980s to detailed studies of the Marmelalke, which uses these trees as a nesting site. As a result of this research, a number of new techniques were introduced in field ornithology, including the use of video surveillance and radars.

Genera and species

The crested alf
Riesenalk, lithograph by John Gould . From: "The Birds of Europe" (1832–1837)

literature

  • Anthony J. Gaston and Ian L. Jones: The Auks . Oxford University Press, Oxford 1998, ISBN 0-19-854032-9 .
  • Renate Kostrzewa: The Alken des North Atlantic - Comparative breeding ecology of a group of sea birds , Aula-Verlag, Wiesbaden 1998, ISBN 3-89104-619-7 .

Web links

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

Individual evidence

  1. ↑ a b c Kostrzewa, p. 15.
  2. ↑ Hans-Günther Bauer, Einhard Bezzel and Wolfgang Fiedler (eds.): The compendium of birds in Central Europe: Everything about biology, endangerment and protection. Volume 1: Nonpasseriformes - non-sparrow birds , Aula-Verlag Wiebelsheim, Wiesbaden 2005, ISBN 3-89104-647-2 , p. 558.
  3. ↑ Gaston et al., P. 209.
  4. ↑ Gaston et al., P. 232.
  5. ↑ Gaston et al. P. 210.
  6. ↑ Gaston et al., P. 197.
  7. ↑ a b Gaston et al., P. 198.
  8. ↑ Gaston et al., P. 199.
  9. ↑ a b Kostrzewa, p. 20.
  10. ↑ a b Kostrzewa, p. 17.
  11. ↑ BirdLife factsheet on the Kurzschnabelalk , accessed on October 17, 2010.
  12. ↑ Gaston et al., P. 201.
  13. ↑ Gaston et al., P. 15 and p. 16.
  14. ↑ a b c d Gaston et al., P. 16.
  15. ↑ a b c Gaston et al., P. 17.
  16. ↑ a b c Gaston et al., P. 18.
  17. ↑ Gaston et al., P. 19.
  18. ↑ Rotschnabelalk on Avibase , accessed on October 22, 2010.
  19. ↑ Gaston et al., P. 20.
  20. ↑ Gaston et al., P. 20 and p. 21.
  21. ↑ Gaston et al., P. 21.
  22. ↑ Gaston et al., P. 22 and p. 23.