Great Black-backed Gull (Larus marinus)

[order] CHARADRIIFORMES | [family] Laridae | [latin] Larus marinus | [UK] Great Black-backed Gull | [FR] Goeland marin | [DE] Mantelmowe | [ES] Gavion Atlantico | [NL] Grote Mantelmeeuw

Subspecies

Physical charateristics

Largest gull in the Western Paleartic, with large wings, massive head and bill. White head, underbody and tail, with slaty black back and upperwings. Bill yellow, with red gonydeal spot. Legs pink, iris yellow, with red orbital ring. Juvenile heavily mottled white and pale brown, with all dark bill.

Listen to the sound of Great Black-backed Gull

[audio:http://www.aviflevoland.nl/sounddb/G/Great Black-backed Gull.mp3]

Copyright remark: Most sounds derived from xeno-canto

Range

North America, Eurasia : coastal East North America and West Europe

Habitat

Sandy or rocky coasts, estuaries and open sea. Locally larger inland waters, fields and moorland.
Breeds on vegetated islands, dunes, flat-topped stacks, sometimes salt-marsh islands among bushes.

Reproduction

Breeding period from April to May. Small colonies, near or intermingled with Herring Gull, and often solitary pairs among other species. Chick mortality increases with number of neighbouring territories and frequency of agonistic encounters. Prefers ridges, pinnacles and rock outcrops, but some nest on roofs. Normally uses open sandy, grassy or rocky substrate.
Bulky nest of dry grass, moss and seaweed, often next to rock or vegetation. Clutch size 3 eggs, incubation 27 days. Chick pale grey with large black spots. First breeding at 4 years.

Feeding habits

Omnivorous and opportunistic. Fish, birds and their chicks and eggs, mammals, invertebrates, insects, carrion, rubbish, offal and sometimes berries.
Aggressive predator, particularly on eggs and chicks of Hring Gull and Black-legged Gull. Can kill adult birds. Cracks molluscs and goose eggs by dropping them on hard surfaces, Kills young birds in same way.
Scavenges on shore, also at rubbish dumps.

Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Migration

Shows continuum from completely migratory north of Arctic Circle to merely dispersive in southern parts of breeding range. Essentially a North Atlantic and west European species at all seasons; main European winter range extends south to Bay of Biscay, while smaller numbers occur along coasts south to Morocco. Generally scarce inland, especially so in landlocked countries, but will occur locally in numbers in River valleys of maritime countries where these hold favoured feeding or roosting sites.

Distribution map