Guillemot

from Wikipedia, the free encyclopedia
Guillemot
Guillemots, Bear Island, Svalbard

Guillemots, Bear Island , Svalbard

Systematics
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Alkenbirds (Alcidae)
Genre : Lummen ( Uria )
Type : Guillemot
Scientific name
Uria aalge
( Pontoppidan , 1763)

The Murre ( Uria aalge ) is one of two species in the genus of Lummen ( Uria ) within the family of auk (Alcidae). It only stays on land during the breeding season. The species is represented in a circumpolar manner and breeds in the boreal and subarctic regions. Among the recent Alkenvögeln it is the largest species. Your name has the guillemot, as they, because of their "idiot moderate" seemingly Ganges in contrast to the Razorbill not on the toes , but on their tarsi running. An etymological explanation derives the name from the French name "Guillemot de Troïl", which was initially translated as Troïl-Lumme, from which the name Guillemot developed.

Large colonies are mainly found where cold and warm ocean currents meet. Their breeding grounds are steep cliffs with narrow ledges or small protrusions. The number of subspecies is debatable. At least five, but some authors also seven subspecies are distinguished.

The only Central European breeding site is on Heligoland , where 2,600 breeding pairs were breeding at the beginning of the 21st century. Between mid-2015 and early 2016, tens of thousands of dead guillemots were washed ashore on the American west coast and in Alaska. According to researchers, the reason for the mass deaths was food shortages due to high sea temperatures. At the beginning of February 2019 there was a mass extinction with tens of thousands of dead birds, and several thousand guillemots were washed ashore on the North Sea coast of the Netherlands .

Appearance

Guillemot in winter dress
Flight image of a guillemot
Guillemots, Spitzbergen, including three so-called glasses or ringlets with white circles under the eyes

With a size of 38 to 46 centimeters, the guillemot can be compared to a mallard , but has a thinner and more pointed beak. The wingspan of adult birds is 61 to 73 centimeters and the weight is one kilogram. Together with the thick-billed mum, they belong to the heaviest types of alkenes still alive. The sexual dimorphism is only very slight. On average, males have a slightly larger beak than females.

In summer the plumage on the head, on the back, on the tail, on the upper side of the wings and on the wing tips is brown-black in both sexes. The belly and larger areas of the underside of the wings are white. In winter, the chin and an area behind the eye are also white. During flight, the beak and the gray-black feet stand out clearly from the rest of the body. As a special external feature, a white eye ring can sometimes be seen, from which a white line extends back to about the middle of the head. Animals that show this trait are also known as glasses or ringlets . However, the eye ring is not an indicator of its own species or subspecies, but just a color variant. The color variant occurs on a north-south gradient of 50 percent in the arctic populations to zero percent in Portugal.

The guillemot swims on the water with alternating paddling movements of the feet and is therefore relatively slow. Fleeing guillemots therefore appear or fly. Guillemots moult after the young birds have left the breeding colony. Since they molt the hand wings at the same time, they are then unable to fly for a period of 45 to 50 days. In the male, the inability to fly occurs during the period in which it accompanies its young bird on the sea. Guillemots are relatively poor fliers who move with quick flaps of their wings. The birds take off for flight only after a long approach over water.

Newly hatched nestlings have thick down with fine tips. The down is short on the underside and longer and rougher on the head and neck. The head and neck are black, but the dune tips combined in white sheaths result in a fine, light stripe. The upper body is sooty dark brown with gray flecks. In contrast, the underside of the body is brownish-white, the stomach is usually pure white. The first feathers appear when the nestlings are a few days old.

Guillemots are very vocal in the colonies . Mainly, they emit a nasal wha wha wha which turns into a roaring sound.

distribution and habitat

The breeding area of ​​the guillemot, which is active during the day and at dusk, extends over the coasts of the North Atlantic and North Pacific as well as the adjacent Arctic coasts . In the Atlantic, the breeding colonies are in the west between the 43rd and 56th parallel north and in the east between the 40th and 75th parallel north. In the Pacific, they breed on the Asian coasts between the 40th and 70th north latitude, on the North American Pacific coast their breeding area ranges from the 36th north latitude to the 68th north latitude in Alaska. Within Germany it only breeds on Heligoland , where it lives on the Lummenfelsen . Only fifteen percent of the North Atlantic guillemot population breed on the Canadian coast, but Funk Island is home to an estimated 400,000 pairs of the world's largest breeding colony of this species. Guillemots are one of the most common seabirds in the British Isles. The largest colony sites are on the small Scottish island of Handa , where almost 100,000 guillemots brooded in the 1990s, and on the cliffs of Fowlsheugh near Aberdeen , where around 52,000 breeding birds are counted.

Outside of the breeding season, some of the guillemot populations can be found near their breeding colonies. Other populations, on the other hand, sometimes migrate far. They move in a southerly direction to avoid the sea ice. However, breeding birds of the Oregon and Washington coasts also fly north and stay in the waters off British Columbia in late summer, for example. Large numbers of guillemots gather near Dogger Bank in the North Sea in July . Another large number of guillemots that breed along the British coast congregate in the east of the North Sea after the breeding season, where they mingle with breeding birds of northern Norway. Young birds stay in the shelf region during their first two years of life. Until they fled, they are accompanied by at least one adult bird that is temporarily unable to fly because of the moult. The young birds do not return to their original breeding colony until they are three years old at the earliest.

food

Guillemots, Svalbard fishing

The guillemot feeds mainly on schooling fish such as herring , sand eel , sprat and cod that live near the surface of the water. In arctic regions, crustaceans make up a large proportion of the diet during the summer months . Adult guillemots held in captivity require between 280 and 320 grams of food per day. This corresponds to around 28 to 34 percent of your body weight. The animals are often seen with fish in their beak, with the ends of the fish sticking out. In the North Sea, the feeding areas are on average up to thirty kilometers away from the colony site during the breeding season. On the other hand, in Newfoundland the birds seek out different feeding grounds during the breeding season. During the period in which the egg is incubated, they cover an average of 38 kilometers per flight. In the time in which the nestling is raised, however, only 5.4 kilometers.

During the dives, the guillemot moves underwater with twisting and flapping movements of the wings. The maximum diving depth is 180 meters, but the birds usually dive at significantly shallower depths. Together with the thick-billed mum, they are the species among the alken birds that can dive deepest. This is due to their body mass. Typical of the guillemot's hunting behavior is that at first it only sticks its head into the water up to its eyes and thus observes the fish. The average dive time is one minute per dive. However, dives of 2 to 3 minutes for this species have also been proven.

During the rearing of young guillemots adapt to changes in the food supply by adjusting their search behavior and their daily ration. Studies of breeding colonies on the Shetland Islands have shown that guillemots spend 178 minutes per flight for food in years with little food, more than twice as much time as in years with plenty of food. In these, food flights take an average of 76 minutes. In years with little food they also move six times as far from the breeding colony location as in years with plenty of food and then five times their diving time per feeding flight to 6 to 8 minutes. Even so, the guillemot is unable to fully compensate for a significant decrease in available food. The reproduction rate therefore decreases in years with little food.

Reproduction

Typical guillemot rock on the Orkney Islands

Guillemots reach sexual maturity at the earliest as four-year-old birds, but they are usually only ready to reproduce in the fifth year. Depending on the geographical latitude, they return to their breeding colonies between February and May. Breeding colonies, in which there is great intraspecific competition for nesting sites, are visited by guillemots every few days for a few hours, even in autumn and winter. They demonstrate their claim to ownership for next spring and thus strengthen their cohesion in the brood. Such behavior has been observed on the Isle of May , for example .

Guillemots lead a monogamous seasonal marriage with a high breeding place and thus also partner loyalty. They breed on the coast on ledges and ledges of cliffs as well as on the plateaus of freestanding pinnacles. Other sea birds are also tolerated in the colony. No other alcohol tolerates such close proximity to the nearest neighbor within the breeding colony. In the high season, up to 20 couples can share one square meter. In some cases, however, 50 breeding pairs per square meter were counted.

Clutch

Egg, Museum Wiesbaden collection

Guillemots raise one brood per year. The birds of the Atlantic population lay their eggs between May and July and the Pacific guillemots between March and July. A single egg weighs an average of 108 grams and is incubated by the parent birds on the tarsi. The egg is top-shaped, which has been interpreted in the literature to mean that it protects the egg from falling off the cliff. In various rolling tests it could be shown that the gyroscopic movement is larger than the width of the ledges on which guillemots breed. Especially at the beginning of the brood there is a risk that it will fall from the narrow rock ledge when changing partners. Guillemot eggs have cone-shaped nanostructures on the eggshells. On the one hand, this gives them a rougher surface and thus greater slip resistance. On the other hand, the nanostructure prevents the gas exchange from being reduced by salt deposits. Breeding pairs that have started breeding very early in the season lay in 88 to 90 percent of cases within the next fourteen days a new clutch. On the other hand, breeding pairs that start breeding later only have clutches in 40 percent of cases.

The eggs vary in color and pattern. Common colors are white, green, bluish, or greyish with dots or grains of black or purple. Both parents incubate the egg for 28 to 34 days, alternating about every twelve hours.

Young bird

The young birds are extreme poopers and seek contact with the rock face when they are not being huddled . They show what is known as negative phototaxis , as they instinctively turn away from the light. This behavior protects the young birds from falling. The parent birds also show this behavioral characteristic and breed and roam with their backs to the abyss.

Young guillemots also have a strong drive to maintain parental contact. In exceptional cases it has even been observed that young birds briefly slip into neighboring birds. The young birds are hovered by the parent birds for a very long time, although they can regulate their body temperature by themselves as early as nine to ten days. Even young birds that are already 20 days old are looked after by one of the parent birds for 75 percent of the day. Only young birds that are ready to jump show a greater tendency to move on the ledges.

Fish is always entered lengthways in the beak of the parent birds, so that the food remains invisible to the breeding neighbor. While feeding, spreading the wings prevents the neighbor from stealing food. Young birds are fed by their parent birds between three and five times a day, depending on their age and food availability.

When the young are around three weeks old, they jump off the cliffs, although they cannot yet fly actively with their mesoptile dress, as the flight feathers have not yet formed. With their short stubby wings spread out, they sail from the steep cliffs into the sea. In doing so, they let far-reaching, bright and drawn calls be heard, which serve to promote family cohesion. Young guillemots sometimes fall straight onto the stony beach from a height of 40 meters. Because of the layer of fat that the animals have previously eaten, most of them survive this fall so that they can follow the parent bird out to sea. However, numerous young birds die when they hit cliffs or are hurled against rocks with the waves. An adult parent bird, usually the male, usually flies with the jumping young bird. But it usually waits down on the beach and waits for the chicks there, who occasionally have to cross the stretch between the beach and the surf. Parents and young birds recognize each other by their calls. The jump takes place preferably at dusk. In the Arctic it takes place around midnight, when the light intensity is lowest. The jump is usually very synchronous, so that several thousand chicks leave the hatchery within a few hours. At sea, the young birds are cared for by the males for another 53 to 70 days. Only then are they independent.

More recently it has been observed that guillemots often breed near cormorants . It is believed that this gives them better protection from predators such as ravens and seagulls .

Breeding success and life expectancy

Guillemot Colony

In undisturbed breeding colonies there are 70 to 75 jumping young birds for every 100 breeding pairs that are laying. There is less breeding success in places where there is insufficient food. Around 60 to 80 of every 100 guillemots flown out die by the time they reach sexual maturity. The mortality of young birds is very high, especially in the first autumn, with guillemots flown out early have a significantly higher chance of survival than young birds that are hatched three weeks later. In order to keep the population at least constant, about 24 must reach sexual maturity for every 100 young birds flown out. According to investigations on ringed birds on Heligoland , of 100 young birds found dead, two fall victim to hunting, 42 to fishing and 24 perish due to oil-contaminated plumage. The ornithologist Renate Kostrzewa points out, however, that recoveries are not representative, as they also depend on the circumstances of the find. Birds that die of natural causes are relatively seldom found.

As with many other alken birds, the commercial use of the guillemot was the main source of danger in the past. Guillemots were hunted intensively and their eggs were collected, which in some areas led to a significant decline in populations. These traditional practices still exist today to a much lesser extent in Norway, the Faroe Islands and Great Britain. The most important risk factors recently include increasing and creeping oil pollution in the North Sea, which both immediately leads to significant direct losses due to oil-contaminated plumage and has indirect effects on breeding success. Even in cleaned birds, the mortality rate is very high. In the UK, 99.4 percent of cleaned birds died; in the US, the median life expectancy of cleaned birds was less than ten days. Even with adult birds there are high losses in gill nets as well as floating net remnants and other rubbish. Especially in winter, guillemots are at risk of getting caught in fishing nets and drowning. In 2002, 29.2 percent of the ring-marked guillemots in the Baltic Sea were killed in fishing nets. Regardless of this value, it is assumed that 1,500 guillemots per year in the Baltic Sea die from such nets. The intensive use of fish stocks also has an impact on stocks. In addition, a nesting site competition with the northern gannet also plays a role.

Guillemots can live to be over 30 years old. Individuals who reached 38 years or 42 years and 10 months were registered.

Subspecies

Guillemots in the Barents Sea

There are two subspecies in the Pacific. The Pacific subspecies are generally slightly larger than the Atlantic and have longer beaks and wings.

A different number of subspecies is described for the Atlantic area. Individual authors name up to five subspecies, three of which are generally recognized:

  • I.a. eel breeds in the eastern parts of North America, Greenland , Iceland , the Faroe Islands , Scotland , southern Norway and the Baltic Sea .
  • I.a. albionis is a slightly smaller bird that breeds on the coasts of Great Britain , Ireland , Brittany , Portugal, and northwestern Spain .
  • I.a. hyperborea is native to northern Norway, Svalbard and Novaya Zemlya
  • I.a. spiloptera occurs on the Faroe Islands and is characterized, among other things, by a pattern of spots on the lower wings. This subspecies is not recognized by all authors, as the feature of the spotted underwings is also found in birds, for example on the Shetland Islands.
  • I.a. intermedius is very similar in size and plumage to U. a. albionis . It is therefore also disputed whether the distinction between this subspecies is justified.

Atlantic stock

The total Atlantic population is estimated at 2 to 2.7 million breeding pairs and has shown a strong increase in recent years. Of these, between 0.7 and 1.4 million breeding pairs breed on Iceland and a total of one million breeding pairs in Great Britain, Ireland and the Channel Islands. The populations in south-western Europe are now considered endangered after some severe declines, while populations in large parts of Fennos Scandinavia , western Great Britain and Ireland continue to increase.

swell

literature

  • Jonathan Alderfer (Ed.): Complete Birds of Northamerica. National Geographic, Washington DC 2006, ISBN 0-7922-4175-4 .
  • Hans-Günther Bauer, Einhard Bezzel , 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 .
  • Anthony J. Gaston, Ian L. Jones: The Auks . Oxford University Press, Oxford 1998, ISBN 0-19-854032-9 .
  • Collin Harrison, Peter Castell: Fledglings, Eggs and Nests of Birds in Europe, North Africa and the Middle East. Aula Verlag, Wiebelsheim 2004, ISBN 3-89104-685-5 .
  • Renate Kostrzewa: The alks of the North Atlantic - Comparative breeding ecology of a group of sea birds. Aula-Verlag, Wiesbaden 1998, ISBN 3-89104-619-7 .

Individual evidence

  1. ↑ Alderfer: Complete Birds of Northamerica. 2006, p. 282.
  2. ↑ a b guillemot on Digitalefolien.de
  3. ↑ Gerald Jatzek : Song of a sad bird . In: Hans-Joachim Gelberg (ed.): Where do the words come from? Beltz & Gelberg, Weinheim 2011, p. 66.
  4. ↑ a b c d e f Bauer et al.: The compendium of birds in Central Europe. Volume 1, 2005, p. 566.
  5. ↑ Mystery of mass extinction off the American coast solved. In: faz.net . January 15, 2020, accessed January 21, 2020 .
  6. ↑ Netherlands: 20,000 dead birds washed ashore on the North Sea coast. In: faz.net . February 6, 2019, accessed February 7, 2019 .
  7. ↑ a b c d Kostrzewa: The Alken of the North Atlantic. 1998, p. 54.
  8. ^ Gaston et al: The Auks. 1998, p. 135.
  9. ↑ a b c d e f Kostrzewa: The Alken of the North Atlantic. 1998, p. 59.
  10. ^ Birds on the sea and coast . In: Birds of our region . A6 020 06-10 (2). Atlas Publishing House.
  11. ^ Gaston et al: The Auks. 1998, p. 136.
  12. ↑ a b Kostrzewa: The Alken of the North Atlantic. 1998, p. 60.
  13. ↑ a b c Kostrzewa: The Alken of the North Atlantic. 1998, p. 61.
  14. ↑ a b c Kostrzewa: The Alken of the North Atlantic. 1998, p. 62.
  15. ↑ a b c d e Kostrzewa: The Alken of the North Atlantic. 1998, p. 57.
  16. ^ Bauer et al.: The compendium of birds in Central Europe. Volume 1, 2005, p. 567.
  17. ^ Harrison et al .: Fledglings, Eggs and Nests. 2004, p. 173.
  18. ↑ a b Kostrzewa: The Alken of the North Atlantic. 1998, p. 58.
  19. ↑ SpOn
  20. ↑ Kostrzewa: The Alken of the North Atlantic. 1998, pp. 62 and 63.
  21. ↑ a b Kostrzewa: The Alken of the North Atlantic. 1998, p. 63.
  22. ↑ a b c Bauer among other things: The compendium of birds of Central Europe. Volume 1, 2005, p. 568.
  23. ↑ Kostrzewa: The Alken of the North Atlantic. 1998, p. 56.
  24. ↑ WWF ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Secondary catch in fishing nets (Swedish, PDF) @1@ 2Template: Webachiv / IABot / www.wwf.se
  25. ↑ Fåglar bli äldre än vad vi trott. In: Fågelvännen. No. 1, 2006 (Swedish)
  26. ↑ Information from the Swedish Natural History Museum (English) ( Memento of the original from October 23, 2008 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.nrm.se
  27. ^ Gaston et al: The Auks. 1998, p. 134.
  28. ^ Gaston et al: The Auks. 1998, pp. 134 and 135.

Web links

Commons : Guillemot ( Uria aalge )  - album with pictures, videos and audio files