Common gull

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Common gull
Common Gull (Larus canus)

Common Gull ( Larus canus )

Systematics
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Laridae
Subfamily : Seagulls (larinae)
Genre : Larus
Type : Common gull
Scientific name
Larus canus
Linnaeus , 1758
Flying common gull with recognizable hand wing pattern
Adult common gull in winter plumage; here the American subspecies L. c. brachyrhynchus , which is sometimes viewed as a species of its own.
Common gull in youthful dress
Flying common gull in juvenile dress, here the American subspecies L. c. brachyrhynchus

The common gull ( Larus canus ) is a species of bird within the gulls (Larinae) and the smallest species of the genus Larus . Their distribution is mainly in the temperate latitudes and extends through all of Eurasia and across the Bering Strait in northwest North America from Alaska to central Canada . In the eastern part of North America the species is ecologically replaced by the very similar, somewhat larger and closely related ring-billed gull . The American subspecies is also viewed by some authors as a distinct species.

The common gull usually breeds in smaller colonies of up to 50 pairs, but there are also larger colonies with several thousand pairs on the coast. The nest is usually built on the ground, but can also be elevated and even tree nests occur. Like most seagulls, the species feeds on an omnivorous diet . The largest breeding populations are found in coastal areas, but river landscapes, bogs and swamps inland are also populated. While in Europe many birds only migrate short distances in winter or remain in the breeding areas, the birds in the rest of the range also migrate regularly. The birds of central Eurasia migrate southwest and partly overwinter in the area of ​​the eastern Mediterranean .

The common gull in Europe, like many other gulls, increased sharply during the twentieth century, but was in a slight decline towards the end of the same century. However, the species is not threatened.

description

With a body length of 40–45 cm and a wingspan of 100–130 cm, the common gull is somewhat larger than a black-headed gull and significantly smaller than a herring gull . It is, so to speak, a delicately built version of the larger Larus species. Compared to the herring gull, the head appears more rounded, the beak finer, the wings narrower. A sure distinguishing feature between adult animals is the completely different eye color. When seated, the common gull's chest appears arched and the abdomen slim. The flight seems leisurely with powerful wing beats; in gliding the wings are angled a little. The sexes do not differ. Young common gulls are fully colored from the third year on.

Adult dresses

The bill and legs of adult birds in breeding dress are yellow; the color varies between orange-yellow and greenish-yellow. The iris is brown, the eye is surrounded by a red orbital ring. The head, neck, underside, rump and tail are pure white. The top is bluish gray. As with all Larus species, the wing has a broad, white rear edge. The wing tip is black with a white subterminal mirror on the outer wings and white tips. The black coloring extends over the six outer hand wings and the expansion decreases towards the arm wing, so that it is only limited to a subterminal band on the fifth hand wing. When the bird is sitting, the white tips of the hand wings, which protrude 5–7 cm above the tail, appear as fine white dots. Also striking are the broad, white tips of the umbrella feathers in the sitting bird.

In the simple adult dress, the head is dashed gray-brown washed out. The dashed lines are condensed on the vertex and on the eye; it also becomes coarser in the neck and often looks streaky here. The beak is pale yellowish to light blue-gray and shows a narrow, black band on the front part, which is bent slightly towards the tip on the upper and lower beak so that it appears Z-shaped. The legs are greenish yellow.

Subadult dresses

When young, the beak is dark with a lighter base. The eye is dark. The top of the head, neck and sides of the neck are washed out, gray-brown, blotchy or dashed on a whitish background. The washed-out drawing condenses around the eye, on the ear covers and in the neck. It extends to the sides of the chest and flanks; the rest of the underside is dirty white. The front back is relatively monochrome gray-brown. The rest of the back, shoulder feathers, small and medium-sized arm covers appear to be scaled by brown feather centers and light hems. The gray-beige large arm covers, of which only the inner ones have a light lace border and a subterminal, brown center, stand out as a light band.

The dark brown arm wings show a wide, whitish border due to the light tips, which ends on the inner hand wings. The predominantly black-brown hand wing shows a bright field towards the arm wing due to the light bases of the inner hand wings. The lower wing shows a noticeable pattern due to dark lace hems. The rump is light gray-brown, the upper tail-coverts show dark, arrow-shaped drawings in the area of ​​the shaft on a whitish background. The whitish tail wears a broad, brown-black subterminal band. The legs are flesh-colored.

From September this year's birds moult into their first plain dress. The plumage on the head, chest and top is renewed. The head now resembles that of adult birds in winter, but the brown-gray dots often extend to the sides of the chest and flanks. The monochrome light gray coat and back stand out from the still juvenile wing plumage with brownish feather centers and light hems. This contrast increases in spring when the wing plumage is bleached and therefore looks very light. The feature can also be noticeable in flight. The rump is now mostly completely white and is sharply defined against the dark tail band. The base of the beak is visibly lighter than the youthful dress, the legs are still flesh-colored.

In the second winter, the dark beak bandage is usually wider and more conspicuous than in fully colored birds. The covers of the hands are partly still blackish in color, the white tips of the hand wings and the light mirror on the two outer hand wings are not yet as extensive as in adult birds and are therefore less conspicuous. Dark centers can also be found on the umbrella springs; Remnants of the tail band can still be indicated on individual control feathers.

voice

The common gull is especially happy to call during the breeding season and, like all seagulls, has a wide repertoire of calls. The main call (audio sample) is a bright, sometimes slightly squeaky and nasal kiä or kia , which is less powerful and higher than the corresponding call of the herring gull, and can be ranked when excited . The shouting ( long call , audio sample) is higher, in the middle part often more shrill and faster. The “ cat call ” ( mew call ) uttered as a voice and contact call is described as a soft, quiet, sometimes howling or sometimes vibrating oiiiie . A staccato-like, deep gä gä gä or wä wä wä is uttered as an alarm call . The female's begging cry at courtship is a high, fine kliä ; During the copulation that often follows, an increasing and decreasing, deep cackling can be heard (audio sample).

distribution

The nearly circumpolar breeding area of ​​the common gull comprises large parts of the Palearctic and a large part of the western Nearctic .

In Northern Europe, the species occurs in Iceland, the Faroe Islands and almost all of Fennoscandia . It inhabits the northern part of the British Isles and sporadically the southern part. In Western Europe there are also isolated breeding occurrences in France and Portugal. In Central Europe the species only seldom breeds in the North Sea; there are larger occurrences in the Baltic Sea in Denmark, Germany, Poland and the Baltic States. In the interior, individual occurrences reach into the Alpine foothills and Hungary.

Eastward, the distribution extends in a wide belt through all of Asia to Kamchatka , Anadyrgolf and the Kuril Islands . In the south, the area extends there through the Kyrgyz steppe , to Tuva and Lake Baikal , through Daurien and the Stanowoy Mountains . However, south of the Caucasus there are still breeding occurrences in Armenia and northwestern Iran .

In North America, the distribution extends north from Kotzebue Sound in Alaska eastwards through the valley of the Yukon River south of the Brooks Range and through the entire Yukon Territory . In the Northwest Territories, the area extends from the mouth of the Mackenzie River east to the Horton River and south to Great Slave Lake . In a spur it then extends southward into northeast Alberta and into northern Saskatchewan, where the species still occurs regularly as far as Lake Athabasca and Wollaston Lake . Breeding season observations are available from Reindeer Lake , and there were occasional broods as far as northeastern Manitoba . Another foothill runs along the Pacific coast, which also includes the northwest of British Columbia, but then extends in a rather narrow coastal area to Vancouver Island , although the species is missing as a breeding bird on Haida Gwaii .

Geographic variation

Four subspecies are generally recognized. In the Palearctic , plumage color and beak size vary clinically (gradually) from west to east, towards a darker top and more robust beaks. In terms of wing length, the populations of the Central Palearctic have the largest dimensions, the subspecies L. c. Kamchatschensis differs only slightly from this. The nearctic subspecies differs quite significantly, so that some authors regard them as a separate species. This is also supported by genetic findings, but so far has not been widely recognized. L. c. brachyrhynchus is much more delicate with a rounded head and finer beak. The upper side is similar in color to L. c. heinei , is a bit darker than the nominate form . The youth dress and the first winter dress differ significantly. The top is darker, the underside flat brown-gray. Upper and lower tail-coverts are broadly brownish banded so that the dark subterminal band of the tail hardly stands out.

hikes

While the western European common gull populations mostly remain in the area of ​​their breeding grounds or mostly only migrate short distances, the proportion of regular migratory birds and the length of the distances covered to the east increases.

East Siberian birds are pure migratory birds, whose wintering areas extend from the southern edge of the Sea of Okhotsk and Sakhalin southwest to Japan and Southeast Asia. The Central Palearctic populations, on the other hand, migrate south and west and overwinter in the Baltic States, the Black Sea, the Caspian Sea and the Middle East. Birds from Fennoscandia overwinter in an area between Denmark and Great Britain, other European birds mainly between the Baltic States and Great Britain and in France regularly up to the Loire estuary . Smaller numbers can also be found in the Mediterranean area; individual birds reach the coasts of the Iberian Peninsula or North Africa. There are also individual overwintering birds in the central European inland, most of which are Finnish or Russian birds. Also with the subspecies L. c. heinei is to be expected here. They can reach the edge of the Alpine region along the major rivers.

There has been little research into migratory behavior in North America, but it is believed that most birds migrate. They overwinter along the Pacific coast, where the species is found south to Baja California in winter .

The colonies will be cleared from July. Young birds initially disperse in all directions, adults move away more directed. In Europe this is done southwest, the Wadden Sea of ​​the North Sea is then used as a moulting site. In general, most of the adult birds have reached their winter quarters by October, younger birds by December. However, the train can continue into February. In southern Scandinavia, two waves can be felt during the autumn migration, the maximums of which are in late summer and between October and November. The former mainly includes adult, native birds, the latter mainly Russian populations. In between, the migration of subadult birds is much more stretched. The spring migration begins in Europe in mid-February and peaks between March and mid-May. It is mainly the adult birds that pass through until mid-April, the majority of the annuals from the end of April. The populations of North America and Asia show a similar migration phenology .

habitat

The common gull is very adaptable in terms of its habitat and breeds both on the coast and - mostly in smaller numbers - on inland waters or in swamps and raised bogs. Colony sites must be dry and relatively safe from soil enemies, have low to sparse vegetation and at least have suitable foraging grounds in the wider area. For the latter, considerable flight routes are sometimes accepted, but larger colonies are usually located near grassland or arable land.

In the near-natural habitats of Russia, the common gull bred around the turn of the 20th century, preferably on swampy lake shores or river arms, in steppe swamps, on sandbanks in rivers or on sand plains near the water. Something similar has been reported from North America, where the species occurs during the breeding season in the tundra, in swamps and in inland waters of all kinds.

In the Baltic Sea , the common gull is found as a breeding bird mainly on offshore islands, peninsulas and spits , in the North Sea in dunes , on salt marshes and Halligen , less often on flushing areas . A large breeding colony can be found on an island in the Lower Elbe . In the north of the British Isles , inland bogs , occasionally gravel banks in rivers and, very rarely, cliffs are accepted as breeding grounds. The elevation range here sometimes extends up to 900 m. In Scandinavia, the species sometimes breeds in the swampy tundra , for example in the Hardangervidda , where the highest breeding sites are at 1332 m. However, Felstundra is generally avoided.

In inland Central Europe, the common gull often shows itself as a follower of culture and breeds in gravel pits , in lignite mining areas , at fish ponds or quarry ponds .

Outside of the breeding season, the species is mainly found in the coastal area, and more rarely in inland areas. Usually the littoral , larger bodies of water and estuaries provide the sleeping places from which the feeding grounds are sought. In contrast to the black-headed gull, they prefer generally drier areas such as green or arable land. In the tidal flats, the common gull is found mainly on sandy or solid surfaces. It can also be observed in landfills , but less often in sewage treatment plants or sewers such as the black-headed gull.

nutrition

Like other gulls, the common gull is omnivorous and exhibits a wide range of foraging behaviors. Her main focus is between herring gull and black-headed gull. While the former uses more abundant sources of food, the common gull also often gathers small and widely distributed food, but is much less common than the black-headed gull swimming, shoving or searching for food in low flight; Shock diving is also rare. At landfills, it usually lags behind great gulls and is therefore often only found there in small numbers.

The food generally consists of earthworms , waders or ringworms , insects (especially beetles ), other aquatic or terrestrial invertebrates , smaller fish, grain or fruits. Birds, eggs and small mammals are also part of the prey spectrum. Food spectrum and composition can vary greatly depending on the season, but especially regionally.

In Europe, but partly also in North America, the species can often be found in cultivated land, where it searches for insects and their larvae while plowing in fields or on pastures. In the post-breeding season, food is often sought in the mudflats. In years when vole - gradations can provide much of the food these primarily for breeding season. In some bog areas, the population figures even depend heavily on the number of vole. The rodents are surprised by the shaking flight , killed by beak blows on the head, swung through the water and tumbled until they can be swallowed whole.

In British Columbia, signal crabs have been found to feed on inland lakes , on the coast the common gull catches fish species in tide pools such as the pygmy goby Lepidogobius lepidus or the northern boatswain fish , in the sea the Pacific herring or salmon . Up to 73% of fish was found to be food in the Baltic States, and fish seems to be the main food on the White Sea coast as well.

Especially in winter the kind lives from kleptoparasitism and garbage dumps; in Alaska, the latter sometimes provide the food staple for larger colonies.

Reproduction

Brooding Common Gull
The common gull clutch with three eggs
Common gulls with three young birds

The common gull usually breeds in smaller colonies of up to 50 pairs. There are also large colonies with over 1000 breeding pairs, but these are only found in very few locations in Central Europe. Single breeding pairs often join silver or black-headed gull colonies.

Young birds breed for the first time between two and four years of age, but most (about 60%) breed at three years of age. Common gulls lead a monogamous seasonal marriage, which often turns into a long-term marriage due to the high loyalty of the males to their breeding site and partner. However, the partners always spend the winter separately. New matings are also not uncommon; even if both partners are still alive.

The colony will be occupied from April. At first, this is done hesitantly and by smaller groups, then the majority of the brood population arrives within a few days. However, it can take until the end of May or the beginning of June until the colony is fully occupied. Initially, the birds do not usually spend the night in the colony, but return to their roosts. They only stay in the colony at night after they start building their nests.

Sometimes long-term pairs are paired before they arrive at the breeding site; in some cases, however, the partners only arrive there at a later date. Males then establish a territory, females behave non-territorial. New pairs can be found in the "club", a loose collection of unmated birds in the immediate vicinity of a colony.

  • Common gull breeding colony on an island in the Lower Elbe

  • Clutch with a newly hatched common gull chick; the second chick opens the eggshell.

  • Unlike other seagulls, the common gull also breeds in trees. Here is a breeding site in the crown of a pine

  • Due to its allomimetic gray coloring, the gull chick next to the adult bird is only noticeable through the reflection in the water.

The male chooses the nesting site and very often it is the one from the previous year. It must be as safe as possible from enemies of the soil, weather and flooding. Most of the time, the nest is in less overgrown locations on the ground, especially in the center of a colony, but also in elevated locations. Ground nests are located in inaccessible places such as islets, bushes, headlands, dams or vibrating lawns. Nests in elevated positions on boulders and tree stumps, in pollarded willows or poplars (more rarely in other deciduous trees), in bushes, low conifers or in dead trees. Tree nests are sometimes built by themselves, but old crow or magpie nests are more often used. These are often at heights between 6 and 7 m.

The nest is a flat structure made of plant material, which can vary in size depending on the availability of the nesting material. The diameter is between 20 and 30 cm, the trough is 12-20 cm wide and usually 2-5 cm deep. If unevenness in the ground has to be leveled out, the nest can also be very large. Fine, soft or at least flexible, often wet parts of plants such as grasses, rushes, herbs, roots, mosses, lichens or various fibers are used as nesting material; only rarely also bulky stalks. Only the female builds, the male creates the nesting material from the surrounding area. Often nests from the previous year are repaired.

The eggs are laid about fourteen days after the nest building has started. In Central Europe this is mostly between the last decade of April and the first decade of May. Further north and in mountainous regions later until June.

The clutch consists of two or three, more rarely one or four eggs, which are irregularly spotted black to light brown on a brown or olive ground and are about 57 × 41 mm in size.

After the last or penultimate egg has been deposited, the clutch is incubated by both partners for between 23 and 28 days. The young leave the nest from the age of 4 days and can fly after 28-33 days. They are fed by both parents.

Mortality and Age

Common gulls can reach a considerable age. The highest age of a common gull ringed in Denmark by ring recoveries was 33 years and eight months; in Germany two animals were demonstrably 21 years and eleven and 21 years and seven months old.

Inventory development

During the GDR era, Langenwerder was home to the largest colony of Common Gulls in Central Europe, with up to 10,500 breeding pairs. In 2011, around 1,900 pairs were breeding there.

The worldwide population of the common gull is estimated by the organization BirdLife International at 2,500,000 to 3,700,000 adult birds, according to other estimates it is over a million breeding pairs. The IUCN regards the species as not endangered (“least concern”).

In Europe, as in many species of gulls, populations increased sharply in the middle of the 20th century, which was due to the establishment of numerous sea bird sanctuaries after the Second World War , the increasingly milder climate and the improved food supply in winter. Especially in the British Isles the species was able to record area gains during this time; in addition, Iceland, Poland and Austria were settled for the first time. In Central and Western Europe, the peak was reached around the end of the 1970s, when winter populations were greater than ever before. Then there were declines until the 1990s. By 2000, stocks stabilized again at a much lower level in many places, while slight declines seem to continue in other places. The causes for this differ locally. In part, the pressure of competition from the herring gull is the cause, as in Denmark, where, contrary to the general trend, the decline already occurred in the 1940s. On the other hand, as in Norway, the feeding conditions and consequently the breeding successes have deteriorated. Further sources of danger are loss of habitat, disturbances during the breeding season due to tourist or other activities, the collection of eggs and, locally, the immigration of soil enemies such as foxes or minks on previously uninhabited islands.

There is no information on the population trend for North America. In Alaska, counts showed a breeding population of 1,700 pairs in 44 colonies along the coast. The inland population is estimated to be at least three times as large, and the total population is estimated to be around 10,000 breeding pairs. In Christmas censuses, a winter population of 50,000 birds was found along the Pacific coast. In Prince William Sound , the common gull was one of six breeding bird species whose populations did not recover after the Exxon Valdez disaster and the ensuing environmental disaster. Nothing more is known about the Asian population.

literature

Web links

Commons : Common Gull ( Larus canus )  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c Glutz v. Blotzheim, p. 440, see literature
  2. ↑ a b c Olsen / Larson (2003), pp. 83-92, see literature
  3. ↑ Olsen / Larson (2003), p. 65, see literature
  4. ↑ a b c d e Glutz von Blotzheim, p. 442 and Olsen / Larsson, p. 65f, see literature
  5. ↑ Niels Krabbe: XC25066 Common Gull Larus canus . xeno-canto.org. June 27, 1982. Retrieved November 10, 2019.
  6. ↑ Stuart Fisher: XC44726 Common Gull Larus canus canus . xeno-canto.org. February 14, 2010. Retrieved November 10, 2019.
  7. ↑ a b c Glutz von Blotzheim, p. 447f, see literature
  8. ↑ Olsen / Larsson (2003), p. 65, see literature
  9. ↑ Jarek Matusiak: XC72845 Common Gull Larus canus . xeno-canto.org. March 10, 2011. Retrieved November 10, 2019.
  10. ↑ a b c d BirdLife Species Factsheet, s. Web links
  11. ↑ a b Glutz v. Blotzheim pp. 440 and 450, see literature
  12. ↑ Moskoff / Bevier (2000), section Distribution , see literature
  13. ↑ Olsen / Larson (2003), pp. 73f and 76f, see literature
  14. ^ Robert M. Zink, Sievert Rohwer, Alexander V. Andreev, Donna L. Dittmann: Trans-Beringia Comparisons of Mitochondrial DNA Differentiation in Birds , The Condor 97/3 (1995), pp. 639-649
  15. ↑ a b Glutz von Blotzheim, p. 461, see literature
  16. ↑ a b c d Del Hoyo et al. (1996), see literature
  17. ↑ Glutz von Blotzheim, p. 490f, see literature
  18. ↑ a b Moskoff / Bevier (2000), section Migration , see literature
  19. ↑ Olsen / Larson (2003), p. 76, see literature
  20. ↑ a b c d e Glutz v. Blotzheim, p. 468f, see literature
  21. ↑ Menzbir (1895) quoted in Glutz v. Blotzheim, p. 467, see literature
  22. ↑ Moskoff / Bevier (2000), Habitat section , see literature
  23. ↑ a b c Glutz von Blotzheim, p. 477f, see literature
  24. ↑ Glutz von Blotzheim, p. 486f, see literature
  25. ↑ Glutz von Blotzheim, p. 459, see literature
  26. ↑ a b Moskoff / Bevier (2000), section Food Habits , see literature
  27. ↑ Del Hoyo et. al (1996), see literature
  28. ↑ Glutz von Blotzheim, p. 479, see literature
  29. ↑ a b c d e f g h Glutz von Blotzheim, p. 469f, see literature
  30. ↑ a b c Moskoff / Bevier (2000), section "Breeding", see literature
  31. ↑ Hüppop. K. & O. Hüppop: Atlas for bird ringing on Helgoland, Vogelwarte 47 (2009), page 214
  32. ↑ Glutz von Blotzheim, p. 451, see literature
  33. ↑ The Langenwerder in the statistics. Brutsaison 2011. langwerder.de, 2012, archived from the original on January 8, 2013 ; accessed on June 13, 2017 .
  34. ↑ a b Moskoff / Bevier (2000), section Demography and populations , see literature
  35. ↑ a b c d Glutz von Blotzheim, pp. 457f, see literature
  36. ^ RH Day et al .: Effects of the Exxon Valdez oil spill on habitat use by birds in Prince William Sound, Alaska . Ecological Applications Vol. 7, No. 2, 1997, pp. 593-613, cited in Moskoff / Bevier (2000), section Demography and populations , see literature