[order] Charadriiformes | [family] Laridae | [latin] Rissa tridactyla | [UK] Black-Legged Kittiwake | [FR] Mouette tridactyle | [DE] Dreizehenmöwe | [ES] Gaviota Tridáctila | [IT] Gabbiano tridattilo | [NL] Drieteenmeeuw

Drieteenmeeuw determination

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The Black-legged Kittiwake is a medium-sized gull, with the typical 'gull-like' appearance of white head and body, slate-gray back and wings, black wingtips, and a yellow bill. The legs are black. The juvenile has bold, black edgings on its wings and the nape of its neck, and a black bill. Black-legged Kittiwakes fly with stiffer wing-beats than other gulls.
Black-legged Kittiwakes are surface feeders, dropping from flight to take items off the surface of the water, or plunging into the water for prey just below the surface, but not diving deeply. They also forage while swimming.

A pelagic gull, this kittiwake spends most of the year at sea. The Black-legged Kittiwakes gather in areas of upwellings, sometimes over the edge of the continental shelf. They can be found from the coast to over a hundred miles offshore. They breed on narrow cliff ledges in the far north.

Rissa tridactyla is a widespread but patchily distributed breeder along the Atlantic coasts of western and northern Europe, which accounts for less than half of its global breeding range. Its European breeding population is very large (>2,100,000 pairs), and underwent a moderate increase between 1970-1990. Although the species declined in Greenland, Norway and the United Kingdom during 1990-2000, and underwent a moderate decline (>10%) overall, this decline is probably outweighed by the earlier increase.
Atlantic populations have experienced growth in recent years. Pacific populations of Black-legged Kittiwakes fluctuate dramatically. They are relatively insensitive to the direct effects of oil spills, but they are indirectly affected by a reduction in prey species. In years when food is scarce, their nesting success is significantly reduced. In addition to the obvious effects of lack of food, when prey is scarce, the adults range farther from the nest and are away for longer periods of time, leaving the eggs and the young exposed, and thus more vulnerable to predators. Years of near-total breeding failure for colonies have been observed in years when the diving birds in the same area do not experience a similar decline, indicating that surface feeders may be responding to different environmental disturbances than diving birds. For this reason, Black-legged Kittiwakes have been proposed as a good indicator species of marine health.

Small surface-schooling fish make up the majority of the Black-legged Kittiwake's diet. When these fish aren't available, the kittiwakes eat krill and other sea creatures. They occasionally feed on waste from ships. Black-legged Kittiwakes do not feed at garbage dumps as do many other gull species.

This species has a large range, with an estimated global Extent of Occurrence of 1,000,000-10,000,000 km². It has a large global population estimated to be 17,000,000-18,000,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]

Black-legged Kittiwakes are monogamous during the breeding season, but do not maintain their pair bonds during the non-breeding season. Many will, however, re-pair with the same mate in the following year. They first breed at 3-5 years of age. On a narrow cliff edge, both parents help build a nest of mud, seaweed, and grass with a shallow depression in the middle. The female lays 1-3 eggs, and both sexes help incubate for about 4 weeks. The young stay in the nest for 5-8 weeks, and both parents provide food. After fledging, the young may return to the nest for a few more weeks. The nest ledges are so narrow that the birds must face towards the cliff, with tails pointed out, to fit.

Not truly migratory; extensive movements by European birds involve dispersals into and even across North Atlantic, with immatures in particular reaching Canadian coasts. pelagic during immaturity and (when adult) outside period of colony attendance. Transects show presence all across North Atlantic in winter (October to March or April), though all age-classes virtually absent from mid-ocean in summer when concentrated off continental coasts and around colonies. In Britain, adults continue to visit colonies through the autumn, even into November; after short absence, begin reoccupation about February. In far north (e.g. Spitsbergen, Murmansk) adults absent September-October to March-April