Glaucous gull

Glaucous gull
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Laridae
Genus: Larus
Species: L. hyperboreus
Binomial name
Larus hyperboreus
Gunnerus, 1767

The glaucous gull (Larus hyperboreus) is a large gull, the second largest gull in the world which breeds in the Arctic regions of the Northern Hemisphere and the Atlantic coasts of Europe. It is migratory, wintering from in the North Atlantic and North Pacific oceans as far south as the British Isles and northernmost states of the USA, also on the Great Lakes. A few birds sometimes reach the southern USA and northern Mexico.

Description

Adult plumage
Immature plumage

This is a large and powerful gull, very pale in all plumages, with no black on either of the wings or the tail. The term glaucous describes its colouration. Adults are pale grey above, with a thick yellow bill. Immatures are very pale grey with a pink and black bill. This species is considerably larger, bulkier and thicker-billed than the similar Iceland gull, and can sometimes equal the size of the great black-backed gull, the largest gull species. They can weigh anywhere from 960 to 2,700 g (2.12 to 5.95 lb), averaging 1.55 kg (3.4 lb) in males and 1.35 kg (3.0 lb) in females.[2][3] At the colony on Coats Island in Canada, the gulls are nearly 15% heavier than other known populations, with a mean weight 1.86 kg (4.1 lb) in males and 1.49 kg (3.3 lb) in females. Thus, Coats Island glaucous gulls are about the same weight as great black-backed gulls or even marginally heavier and their maximum weight is greater.[4] These gulls range from 55 to 77 cm (22 to 30 in) in length and can span 132 to 170 cm (52 to 67 in) across the wings.[3][5][6] Among standard measurements, the wing chord is 40.8 to 50.1 cm (16.1 to 19.7 in), the bill is 4.9 to 6.9 cm (1.9 to 2.7 in) and the tarsus is 6 to 7.7 cm (2.4 to 3.0 in).[3] They take four years to reach maturity.

The call is a "laughing" cry similar to that of the herring gull but deeper.

Subspecies

There are four subspecies:

Ecology

This species breeds colonially or singly on coasts and cliffs, making a lined nest on the ground or cliff. Normally 2–4 light brown eggs with dark chocolate splotches are laid.

These are omnivores like most Larus gulls, and they will eat fish, insects, molluscs, starfish, offal, scraps, eggs, small birds, small mammals and carrion as well as seeds, berries and grains.

References

  1. ↑ BirdLife International (2015). "Larus hyperboreus". IUCN Red List of Threatened Species (IUCN) 2015: e.T22694343A85048979. Retrieved 4 May 2016.
  2. ↑ Dunning Jr., John B., ed. (1992). CRC Handbook of Avian Body Masses. CRC Press. ISBN 978-0-8493-4258-5.
  3. 1 2 3 Olsen, Klaus Malling; Larsson, Hans (2004). Gulls of North America, Europe, and Asia. Princeton University Press. ISBN 978-0691119977.
  4. ↑ Dunning Jr., John B., ed. (2008). CRC Handbook of Avian Body Masses (2nd ed.). CRC Press. ISBN 978-1-4200-6444-5.
  5. ↑ "Glaucous Gull". All About Birds. Cornell Lab of Ornithology. (2011)
  6. ↑ Harrison, Peter (1991). Seabirds: An Identification Guide. Houghton Mifflin Harcourt. ISBN 978-0-395-60291-1.
  • Harrison, Peter (1996). Seabirds of the World. Princeton: Princeton University Press. ISBN 0-691-01551-1. 
  • Bull, John; Farrand, Jr., John (April 1984). The Audubon Society Field Guide to North American Birds, Eastern Region. New York: Alfred A. Knopf. ISBN 0-394-41405-5. 

External links

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