Black-legged kittiwake (Rissa tridactyla)
|Also known as:||kittiwake|
|Size||Length: 38 - 41 cm (2) (3)|
Wingspan: 91 - 97 cm (2)
|Weight||305 - 525 g (2) (4)|
The black-legged kittiwake is classified as Least Concern (LC) on the IUCN Red List (1).
The black-legged kittiwake (Rissa tridactyla) is a small, graceful, cliff-nesting gull, named for its loud, nasal ‘kitti-wake’ call (3) (5) (6). As its common name suggests, its short legs are usually black, helping to distinguish this species from the red-legged kittiwake, Rissa brevirostris. However, in a few rare individuals the legs may be orange or reddish (2) (3) (7). The hind toe of each foot is reduced to a mere bump, meaning there are only three functional toes instead of four, giving the black-legged kittiwake its scientific name, tridactyla, which means ‘three-toed’ (3) (4) (7).
The head and underparts of the black-legged kittiwake are white, while the upperparts and wings are blue-grey. The tips of the wings are black, giving the appearance of having been dipped in ink (2) (3) (4) (5) (7), and the tail is slightly forked (3) (5). The black-legged kittiwake’s bill is yellow, the inside of the mouth is a striking orange-red, and breeding adults have a narrow ring of red around the eye (2) (3) (4) (7). Outside of the breeding season, the adult black-legged kittiwake has darker grey marks around the crown and the back of the neck, and a dark mark behind the eye (2) (5) (7).
The male and female black-legged kittiwake are similar in appearance, but the female may be slightly smaller than the male (3). Juveniles are recognised by a distinctive black zig-zag pattern across the wings, forming a partial ‘M’ shape, as well as by a black collar around the back of the neck, dark patches on the neck and behind the eyes, a black tip to the tail, and a dark to pale yellow beak (2) (3) (4) (5).
The black-legged kittiwake is divided into two subspecies, Rissa tridactyla tridactyla and the slightly larger Rissa tridactyla pollicaris, which is also distinguished by its blacker wing tips and more developed hind toe (2) (3).
This species nests on coastlines and islands across much of the North Pacific and North Atlantic Oceans, as well as on islands off the northern coasts of Russia and Norway (2) (3) (8). R. t. tridactyla breeds in the North Atlantic, from northern Canada and the northern United States, through Greenland, western and northern Europe, and east as far as the northern Taymyr Peninsula and Severnaya Zemlya in Russia. R. t. pollicaris breeds in the North Pacific, from north-eastern Siberia, Kamchatka, the Sea of Okhotsk and Kuril Island, through the Bering Sea and east to Alaska (2) (3) (7).
Outside of the breeding season, the black-legged kittiwake moves from the coast to the open ocean. It winters across most of the northern Atlantic and Pacific Oceans, as far south as Mexico, West Africa and the East China Sea (2) (3) (8).
Unlike most other gulls, the black-legged kittiwake spends most of the year far out at sea, usually out of sight of land (2) (3) (5) (6). It is commonly found over continental shelves and at areas of upwelling, where cool, nutrient-rich waters rise to the surface and result in an abundance of prey (2) (3) (6) (8).
Breeding usually takes place on steep coastal cliffs with narrow ledges, although the black-legged kittiwake will also nest on buildings and other man-made structures (2) (3) (4) (5) (6) (8). It prefers areas with easy access to freshwater (2), but is rarely seen far inland (5). This species sometimes nests unsuccessfully on glaciers or snow where these have covered its traditional nesting sites (2) (3). During the breeding season, the black-legged kittiwake mainly forages near to the coast (3).
The black-legged kittiwake feeds by snatching food from the surface of water or by plunge-diving to take food items just below the surface (2) (3) (4) (6). It usually forages in flocks, often in association with other seabirds, and may occasionally steal food from other species (2) (3). The diet of the black-legged kittiwake consists primarily of fish and marine invertebrates, including squid and shrimps, although it may also take earthworms, birds’ eggs and even small mammals (2) (3) (6) (8). Many different fish species may be eaten, but it often concentrates on one or two locally abundant species, such as sandeels (Ammodytes species), capelin (Mallotus villosus) or herring (Clupea harengus) (2) (3) (6) (9). The black-legged kittiwake also eats some plant matter, including aquatic plants, potatoes and grain, and will sometimes scavenge for offal around fishing vessels (2) (3) (8) (9).
Adult black-legged kittiwakes return to the breeding grounds from January, but breeding does not take place until May and June. More southerly colonies tend to breed earlier, and breeding activity may be delayed by periods of cold weather. The black-legged kittiwake typically nests in huge colonies, which may occasionally number over 100,000 pairs (2) (3) (8). The nests are tightly packed, sometimes even touching (3) (7) (8), and are constructed by both the male and female from compacted mud, feathers, vegetation and seaweed (2) (3) (4) (7) (8). The black-legged kittiwake usually builds its nests on such narrow ledges that the adults and chicks barely fit, and often have to face toward the cliff with their tails hanging over the edge (3) (6) (7).
The female black-legged kittiwake lays 1 to 3 eggs, which are incubated by both adults for 24 to 28 days (2) (3) (6). The chicks fledge at about 34 to 58 days old (3) (6). After breeding, the birds leave the breeding ground from July to August, and the young remain at sea for the first few years of life, not returning to breed until they are three to five years old (2) (3) (6). Black-legged kittiwake chicks are vulnerable to avian predators such as skuas, peregrines, crows and gulls, and the adults are also sometimes killed by great black-backed gulls (Larus marinus) (2) (3) (7). However, surviving individuals may live for up to 13 years (3).
Reported to be the most abundant gull species (2) (9), the black-legged kittiwake also has a widespread distribution and is not currently considered at risk of extinction (8). However, significant population declines have been recorded in some parts of its range, such as in the United Kingdom (8).
The main threats to the black-legged kittiwake include oil pollution and the depletion of its food resources due to over-fishing (3) (7) (8). It is also hunted and its eggs collected in Greenland and parts of North America (2), but this is not thought to be having a severe impact on the species (3) (7). Potential future threats may come from outbreaks of avian influenza and from the possible effects of global climate change on its habitats and prey (8).
The black-legged kittiwake has been the subject of a number of long-term studies and is considered a good indicator of the fluctuating conditions of marine ecosystems (3). Many breeding colonies are monitored and many of the larger colonies are also protected, although most of the smaller ones receive no formal protection (3). This species is listed under the African-Eurasian Waterbird Agreement (AEWA), which calls on parties to undertake conservation action for bird species which rely on wetland habitats for at least part of their annual cycle (10).
Further recommended conservation measures for the black-legged kittiwake include investigating its movements, diet and habitat use outside of the breeding season (3), as well as monitoring hunting and supporting efforts to reduce the risk of oil spills (7).
Find out more about the black-legged kittiwake and its conservation:
BBC Wildlife Finder - Kittiwake (Rissa tridactyla):
The Cornell Lab of Ornithology - All About Birds: Black-legged Kittiwake:
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- Avian influenza: also known as “bird flu”, a contagious disease caused by any strain of influenza virus that is carried by and primarily affects birds.
- Continental shelf: a region of relatively shallow water, not usually deeper than 200 metres, surrounding each of the continents.
- Incubate: to keep eggs warm so that development is possible.
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
- Subspecies: a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
IUCN Red List (February, 2011)
- del Hoyo, J., Elliott, A. and Sargatal, J. (1996) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
Hatch, S.A., Robertson, G.J. and Baird, P.H. (2009) Black-legged kittiwake (Rissa tridactyla). In: Poole, A. (Ed.) The Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
The Cornell Lab of Ornithology - All About Birds: Black-legged Kittiwake (February, 2011)
- Peterson, R.T., Mountfort, G. and Hollom, P.A.D. (1993) Collins Field Guide: Birds of Britain and Europe. HarperCollins Publishers, London.
- Kaufman, K. (2001) Lives of North American Birds. Houghton Mifflin Harcourt, Boston, Massachusetts.
U.S.Fish & Wildlife Service: Alaska Seabird Information Series - Black-legged Kittiwake Rissa tridactyla (February, 2011)
BirdLife International (February, 2011)
Joint Nature Conservation Committee (JNCC) - Black-legged kittiwake Rissa tridactyla (February, 2011)
Agreement on the Conservation of African-Eurasian Migratory Waterbirds (February, 2011)