Ice gull

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Ice gull
Adult ice gull (Larus hyperboreus) in splendor

Adult ice gull ( Larus hyperboreus ) in splendor

Systematics
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Laridae
Subfamily : Seagulls (larinae)
Genre : Larus
Type : Ice gull
Scientific name
Larus hyperboreus
Gunnerus , 1767
Ice gull in flight. A black hand swing pattern like most other great gulls is missing.
Ice gulls in their youthful dress. Note the detached two-colored beak.
Ice gull in the second winter. Towards spring the young birds are almost white in their worn plumage.
Ice gulls towards the end of the breeding season - moulting still in their breeding plumage, in their third plumage and in plumage (from left to right)

The ice gull ( Larus hyperboreus ) is a large bird within the seagulls that inhabit the coasts of the subpolar zone and the polar regions of the Arctic . It winters in ice-free waters in the south of its range, but can also be found in smaller numbers south of it and - especially on weather-related flights - as an occasional guest in the temperate zone.

The ice gull breeds on cliffs and islands, and more rarely on tundra lakes or beaches. It is often found in the vicinity of breeding colonies of other arctic bird species, on whose eggs and young birds it then mostly feeds. The food spectrum also includes fish and marine animals as well as carrion and waste, especially outside the breeding season.

description

With a body length of 62–70 cm and a wingspan of 140–160 cm, the ice gull is somewhere between the silver and the black-headed gull . She is a strongly built great gull with a "grim" facial expression and a sloping forehead. When the bird is sitting, the umbrella feathers form a distinct step and the hand-swing projection is relatively short. In flight, the body looks strong and the wings are shorter than those of a herring gull, with long arm and rather short hand wings. The flight seems a bit sluggish. The translucent wings of the hand - viewed from below - are striking. A black hand swing pattern is missing, as is a black tail band in the youth clothing. A sexual dimorphism does not exist with regard to the plumage. However, females are often significantly smaller and lighter than males. While males of the nominate form weigh between 1 and 2.2 kg, the weight of females is between 0.9 and 1.8 kg. Young ice gulls are fully colored after the fourth winter.

The ice gull resembles the polar gull in all clothes . However, this is smaller with a more rounded head. The flight seems easier and the flight pattern is clearly different.

Adult birds

In its splendid dress, the ice-gull shows a yellow beak with a red gony spot . The iris is light yellowish, the eye is surrounded by a yellow or orange orbital ring. The head, neck, front back, underside and control feathers are pure white. The top is light gray. In contrast to most large gulls, the wing lacks a black hand-wing pattern. The trailing edge of the wing shows a wide, white hem that extends to the tip. Legs and feet are dark pink. In the plain dress, the head and neck are relatively dense and have a dashed gray-brown pattern, except for the front breast.

Youth dresses

A striking feature of young ice gulls, which also distinguishes them from young polar gulls, is the detached two-colored beak with a pink-flesh-colored base and black tip or subterminal band. The legs are also flesh-colored in all clothes. In contrast to other large gulls, there is no dark tail band and a black wing tip.

Young birds are predominantly light gray-brown to "milk coffee brown". The head and underside have a very fine gray-brown pattern. The dark eye is framed by light lids and the area behind the beak is slightly brightened. The shoulder and back feathers appear scaly patterned due to light hems and subterminal dark bands; the beige-gray wing feathers and tail feathers are whitish lined and dark banded or bespitzt. The rump and tail-coverts are banded dark.

Birds in the first winter are similar to those in their youthful plumage, but are lighter. Some specimens - especially in spring with their worn plumage - appear almost whitish with only rudimentary markings. They can be distinguished from older birds by the completely black tip of their beak.

Birds in the second plain dress have a more irregular pattern than birds in the first winter. They look a bit piebald. The head drawing is often clearly dashed, as is typical for the simple dress of the great gulls. The eye and the tip of the beak are already lightened. Towards summer or, for some birds, only at the beginning of the third winter, the light gray feathers of the adult dress mix in the back and shoulder plumage.

In the third plain dress, the back and shoulder feathers are already predominantly light gray. However, some beige-gray feathers with light borders are often retained. The umbrella feathers are even more narrowly lined with white than in the adult dress. Underside, rump and control feathers still show gray-brown spots or feather centers. The black tip of the beak is now reduced to a narrow, subterminal band. The face often looks lighter than in the second winter.

voice

The vocal expressions of the ice gull are much higher than those of the similarly sized jacketed gull and sometimes also higher than those of the herring gull.

The main call is described as üe or two-syllable k-li . The " shouting " ( long call ) is higher and slower than in the herring. Because of the excessive, shrill sounds in the middle section, it is reminiscent of the reverse calls of a donkey ( ai instead of ia ). The "cat call" is described as high, drawn out and whistling. The "staccator call" used as an alarm call is a shrill ga-ga-gak , kek-kek-kek or go-go-gok .

distribution

The breeding distribution of the ice gull extends over the subpolar zone and the polar regions of the Arctic . In Europe it is limited to the northwest and southeast of Iceland , Jan Mayen , Svalbard and Bear Island . In northern Russia and Siberia, it ranges from the Murmansk coast eastwards to the Gulf of Anadyr and includes Franz Josef Land , Novaya Zemlya , Severnaya Zemlya , the New Siberian Islands , the Bennett and the Wrangel Island and the St. Lawrence Island .

In the Nearctic , the ice gull inhabits the northern coasts of Alaska southwards to Bristol Bay . It is absent on the Aleutians and the Pribilof Islands . Inland deposits are found in the foreshore of the Brooks Range and in the Colville River area . It is a common breeding bird on the coasts of the Canadian Arctic Archipelago . The area extends south from Nansen Sound , Greely Fjord and Lady Franklin Bay in northern Ellesmere Island . The ice gull is only missing here in the west of Baffin Island . On the mainland it occurs on the northern coast of Yukon including Herschel Island , on the Adelaide Peninsula and on Boothia , but is absent there in the Rasmussen Lowlands . In Kivalliq there are inland deposits on tundra lakes. It populates the east coast of the Hudson Bay up to the level of the Belcher Islands , where it also breeds. At James Bay it appears only scattered. It also breeds in the far north of the Labrador Peninsula - especially at Ungava Bay , but also southeast to 55 ° N.

In Greenland, the species is a widespread breeding bird on the west coast of Nunarsuit at around 60.4 ° N to Washington Land , but is absent in the area of ​​the Humboldt Glacier and on coastal sections that are densely populated by the black-headed gull. On the east coast, the distribution extends from Cape Farvel to the Germanialand peninsula . Northwards the species is then only found scattered up to about the Jørgen-Brønlund-Fjord .

Geographical variation and hybrids

Up to four subspecies are recognized, whereby L. h. leuceretes is controversial and is often used in the nominate form :

  • L. h. hyperboreus Gunnerus 1767 - Jan Mayen and Spitzbergen, eastward to the eastern Taimyr peninsula
  • L. h. pallidissimus Portenko 1939 - Eastern Siberia between the Taimyr Peninsula and the Bering Sea
  • L. h. barrovianus Ridgway 1886 - Alaska to Western Canada
  • L. h. leuceretes Schleep 1819 - Eastern Mackenzie District , Canadian Arctic Archipelago, Greenland and Iceland.

The geographical variation is relatively weak, so that some authors also consider the species as monotypical . In 1986 Richard C. Banks subjected the fine systematics of this kind to a closer examination. According to him, the birds of the western Nearctic are relatively small, dark on the top and have quite small beaks ( barrovianus ). The populations from the eastern MacKenzie eastward to the Taimyr peninsula (previously listed as nominate form) are larger and more large-beaked , while the birds east of the Taimyr peninsula are largest and brightest, with the strongest beaks ( palidissimus ). So in terms of size there is an increase from west to east with a clear border on the Bering Sea .

In addition, according to Banks, the nominate form could be broken down into the birds of the eastern Nearctic, Greenland and Iceland, which are quite light on the top, and a darker population from Jan Mayen and Spitsbergen to the east. As a subspecies name he suggests leuceretes , based on Bernhard Christian Schleep's description of a Greenland bird from 1819 from a collection in Schleswig . Other authors don't follow suit. In their opinion, the populations of the previous nominate form do not differ. In contrast to European birds, East American birds are often lighter in the first winter, but this is not necessarily the rule.

The ice gull hybridizes not infrequently with the herring gull or the American herring gull . The latter hybrids are also known as "Nelson's Gull" and occur particularly in the Mackenzie Delta and northeastern Canada, the former especially in southwest Iceland and the Kola Peninsula . In western Alaska, hybrids with the bering gull are common and locally account for up to 50% of the population. They also occur in the east of the Bering Sea. In Greenland there are regular hybrids with the black-headed gull.

hikes

Two ice gulls (top right and bottom left) in an Ontario winter flock of seagulls
Ice gull nesting rocks, like here in West Greenland, are often characterized by orange-yellow lichen growth.
Ice gulls in the wake of a polar bear family

The glaucous gull is a partial migrant , who mostly spends the winter in the southern part of the breeding distribution in ice-free waters. In smaller numbers, the species is also a regular winter visitor in parts of the cold-temperate zone . Especially on weather-related flights, it also reaches further south.

West Greenland birds are largely resident birds , the birds of the east coast overwinter largely in Iceland, in smaller numbers also on the British Isles and in the North Sea area . The birds of the Western Palearctic are short-range migrants that often overwinter in Northern Norway . East Siberian birds overwinter on the East Asian Pacific coast south to Japan or, more rarely, East China . In severe winters, several hundred specimens gather in the fishing ports of Hokkaidō . The species reaches Hong Kong as an odd visitor .

There are two migration routes in the Nearctic. The populations on the Beaufort Sea and to the west of it move south on the Pacific coast, overwinter mostly in the Aleutian region and in smaller numbers south to California . The breeding birds of northeastern Canada migrate along the coast of Labrador. There are large winter populations here in Newfoundland with over 1000 specimens. Immature birds in particular seem to be more frequent than previously assumed in the pelagic area in the area of ​​the Labrador Current and the Newfoundland Bank. The species is less common southwards to Long Island, with some moving to the Great Lakes area . As a stray visitor she reaches Bermuda , Mexico or Hawaii .

The breeding grounds are cleared between September and mid-October. This year's birds often only migrate when the sea freezes over. Sometimes even dismigrations to the north take place in the post-breeding season. They move home between February and April. From April to May (in high Arctic regions until the end of May) the colonies are reoccupied in spring.

habitat

The ice gull breeds in steep walls and cliffs as well as on rock islands or pinnacles, which are mostly located on the coast, more rarely a few kilometers inland. Protected areas in fjords are preferred to exposed areas facing the open sea. Where the nesting sites are safe from soil enemies, the species also breeds on flat islands, on beaches, inland lakes or river banks. The proximity of the breeding sites to important food sources is striking. The breeding grounds of the ice gull in the high Arctic are often in colonies of sea birds , geese or eider ducks as well as in the vicinity of human settlements. The highest colonies are found at 1000 m above sea level.

The habitat requirements of the ice gull are very similar to those of the black-backed gull, which apparently often competes for nesting sites. In West Greenland, therefore, the ice gull is absent on coastal sections densely populated with black-headed gulls. In West Iceland she prefers seaward facing cliffs with strips of grass as a nesting place - possibly an adaptation to competition with black-headed gulls. Where it is socialized with other cliff breeders such as guillemots , three toed gulls , polar or Thay gulls, the ice gull often occupies the highest nesting places, with a little distance above the other breeding birds. Colony sites are often characterized by a conspicuous vegetation with orange-yellow lichens of the genera Caloplaca or Xanthoria . In addition, grasses and nitrophilic flowering plants often grow particularly lush below the colonies .

Outside the breeding season, the ice gull can be found in the area of ​​the ice-free coasts and rarely only inland. In contrast to the breeding season, it then also extends its activities into the shelf zone . It can also be found at landfill sites, fishing ports, in settlement areas or in fields, and more rarely on large inland waters.

nutrition

Like many gulls, the ice gull feeds on an omnivorous and opportunistic diet . The focus is clearly on animal food. The choice of breeding site and daily activity are particularly clearly based on the food available in this species. Depending on the occasion, it feeds fishing, collecting, predatory, as a kleptoparasite or as a scavenger.

In the intertidal zone and in the pelagic it collects or prey on marine invertebrates and fish. These include triangular crabs such as the Nordic spider crab ( Hyas araneus ), mussels , periwinkles , echinoderms and sand eels . In contrast to the black-headed gull, it hardly catches large fish, but uses even the smallest remains of fish. Since it cannot dive deeper than 1 m, it usually catches marine animals from the surface of the water. Occasionally, disintegrating or overturned icebergs reveal a rich supply of food, which then attracts entire swarms.

Particularly during the breeding season and in high Arctic areas, the ice gull lives on colonies of sea birds, geese or ducks. Eggs and young birds play a role as food. The range of crab divers or guillemots flying out is used extensively. In the Yukon, Canadian chicks , emperor goose and white-fronted geese made up a large proportion of the gastric contents examined. But adult birds from the size of a snow bunting to black guillemots are caught and devoured whole. Mammals such as lemmings , brown rats or newborn ringed seals are also part of the food spectrum and are generally killed by beak blows.

If the seabird colonies are cleared at the end of the breeding season, this can lead to increased mortality among the remaining ice gulls. On the other hand, the species uses even the smallest food sources quite efficiently, especially outside the breeding season. It leaves only skin and bones on carcasses and also consumes afterbirth or the feces of arctic foxes , polar bears or seals. Plant foods such as intoxicants or crowberries are also eaten. Several thousand birds can gather at abundant food sources within a few days. Above all in the south of the distribution area, rubbish dumps, waste in settlements or fish scraps in ports or industrial areas are used extensively. The species is often found in the wake of fishing trawlers.

Reproduction

Egg, Museum Wiesbaden collection

Ice gulls reach sexual maturity at four to five years of age and have a monogamous seasonal marriage. Annual breeding takes place, with some pairs not breeding in years with poor feeding conditions.

The ice gull arrives in the breeding areas in April or early May. The pairing takes place at the nesting sites and can drag on for some birds until the beginning of June. Nest building and egg laying can be delayed by unfavorable weather and late snowmelt. However, the former usually takes place in the course of May and the latter in late May or early June, on Svalbard but also sometimes in the first May decade and in the Lower Arctic from mid-May.

The ice gull breeds in single pairs or colonies of usually up to 150, rarely up to 1000 pairs. Couples who specialize in eggs and young birds from other colony breeders as food during the breeding season often defend a food territory with a radius of 30 to over 100 m in addition to the vicinity of the nest. Their breeding places are often above those of the other breeding birds. Pairs with a less specialized diet often breed in denser colonies.

The nest location can be very different, but should be safe from soil enemies and is often facing south, as such locations are free of snow earlier. Where the species is followed by humans, the nesting sites are often over 200 m above the ground. Relatively wide ledges are preferred in steep walls or cliffs. Sometimes the species also breeds on hut roofs. If the brood was successful at a nesting site, it will usually be stocked again in the next year.

The nest is built by both partners and, depending on the availability of material, is a more or less extensive construction of around 30–50 cm in diameter. It consists of grasses, tufts of grass, moss, branches of flowering plants, algae, seaweed and feathers. The nesting trough is often not lined. Often only a hollow with a little seaweed is created on gravel banks. In years with late snowmelt, the nest is built by a few couples in the snow and slowly sinks. When the snow thaws and the nest becomes soggy, the clutch is abandoned.

The clutch usually consists of three, more rarely one or two eggs, 76 × 53 mm in size, which are mottled gray or dark brown on mostly light gray, light blue-green or light olive-colored ground. In the event of a loss of clutch, there are laggards, which are usually smaller with two eggs. They are incubated by both partners for about 27-28 days.

The boys are up to the age of 10 days brooded , later sheltered only precipitations in the wings. Feed both parents. After 45–50 days, the young fly out and are given food for a few more days.

Systematics

The ice gull was first described by Morten Thrane Brünnich as Larus glaucus in 1764 . This name lasted until 1908, when the American Ornithologists' Union established that Larus glaucus had been used by Erik Pontoppidan as early as 1763 and was a synonym for the common gull ( Larus canus ) described by Linnaeus in 1758 . The next valid name was now Larus hyperboreus Gunnerus , 1767 and has been used since then. The epithet hyperboreus refers to the high Nordic " Hyperborea " of the Greeks.

Duration

Information on the global population of the ice gull is not very reliable, in some cases contradicting itself and is mostly only based on very rough projections. According to more recent sources (2006), the values ​​are between 340,000 and 2,400,000 individuals, and according to older estimates, more than 100,000 breeding pairs.

For eastern Canada, the population around the turn of the millennium is given as roughly 70,000 individuals in over 1,000 colonies. Here previously unknown colonies are repeatedly discovered during explorations. In Alaska, the total population with a rough estimate of breeding birds in the interior is put at over 100,000 individuals. Estimates for the Western Palearctic are over 20,000 breeding pairs, and for the Eastern Palearctic between 10,000 and 1,000,000 breeding pairs. 30,000–100,000 pairs are said to breed on Greenland.

No data is available on inventory trends. Apart from local or regional decreases or increases, the stock appears stable. The species is classified by the IUCN as Least Concern (not endangered).

literature

Individual evidence

  1. ↑ a b c d Olsen / Larsson (2003), p. 187, see literature
  2. ↑ Olsen / Larsson (2003), p. 197, see literature
  3. ↑ a b c d Olsen / Larsson (2003), pp. 188–191 and pp. 192f, see literature
  4. ↑ a b c d e Glutz von Blotzheim (p. 663, see literature), after Friedrich Goethe: The calls of the ice gull and the herring gull, a comparison . Extended German version of a lecture from July 1972 to the Brit. Orn. Union in Reykjavík. Ornithological station 31, 1982
  5. ↑ Olsen / Larson (2003), p. 192, see literature
  6. ↑ a b Gilchrist (2001), section Sounds , see literature
  7. ↑ a b Glutz von Blotzheim
  8. ↑ Gilchrist (2001), section Distribution , see literature
  9. ↑ a b Banks (1986), p. 153f, see literature
  10. ↑ Mactavish et al. (letter), cited in Olsen / Larsson (2003), p. 195
  11. ↑ Olsen / Larsson (2003), pp. 135, 158 and 193f
  12. ↑ a b Glutz von Blotzheim, p. 664f, see literature
  13. ↑ a b c d e f g h Olsen / Larson (2003), p. 165f, see literature
  14. ↑ Gilchrist (2001), section Migrations , see literature
  15. ↑ a b c d Glutz von Blotzheim, p. 670f, see literature
  16. ↑ a b c d e f Del Hoyo et al. (1996), see literature
  17. ↑ a b Gilchrist (2001), Habitat section , see literature
  18. ↑ Friedrich Goethe: On biology, especially the ethography of the polar gull (Larus glaucoides Meyer, 1822) , Ann. Naturhist. Mus. Vienna. 88/89 (Ser. B), 1986, pp. 116f
  19. ↑ Glutz von Blotzheim, p. 671, see literature
  20. ↑ a b c d e f g Glutz von Blotzheim, p. 672f and p. 674, see literature
  21. ↑ a b Gilchrist (2001), section Food Habits , see literature
  22. ↑ a b Gilchrist (2001), section Demography and Populations , see literature
  23. ↑ a b c d Gilchrist (2001), section Breeding , see literature
  24. ↑ a b c d Glutz von Blotzheim, p. 670f, see literature
  25. ↑ Gilchrist (2001), section Behavior / Spacing , see literature
  26. ↑ Banks (1986), pp. 149f, see literature
  27. ↑ a b BirdLife Species Factsheet, see web links

Web links

Commons : Ice Gull  - Album with pictures, videos and audio files
Wiktionary: Eismöwe  - explanations of meanings, word origins, synonyms, translations