The black-legged kittiwake (Rissa tridactyla) is a seabird species in the gull family Laridae. This species was first described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae as Larus tridactylus. The English name is derived from its call, a shrill 'kittee-wa-aaake, kitte-wa-aaake'. In North America, this species is known as the black-legged kittiwake to differentiate it from the red-legged kittiwake, but in Europe, where it is the only member of the genus, it is often known just as kittiwake.
Taxonomy The black-legged kittiwake was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae. He placed with the gulls in the genus Larus and coined the binomial name Larus tridactylus. Linnaeus specified the type location as northern Europe but this has been restricted to Great Britain. The black-legged kittiwake is now placed together with the red-legged kittiwake in the genus Rissa that was introduced in 1826 by the English naturalist James Stephens. The genus name is from the Icelandic word "rita" for a black-legged kittiwake. The specific tridactyla is from Ancient Greek tridaktulos meaning "three-toed". The English name "kittiwake" is derived from its call, a shrill 'kittee-wa-aaake, kitte-wa-aaake'.
Subspecies Two subspecies are recognised. These are listed below together with their breeding ranges. R. t. tridactyla (Linnaeus, 1758): North Atlantic Ocean, from high Arctic to temperate coasts, in Greenland, Iceland, west and northwest Europe, Svalbard and northwest New Siberian Islands, the Canadian high Arctic (northeast Canada), Gulf of St. Lawrence and Newfoundland (southeast Canada). Unique among the Laridae in having only a very small or even no hind toe. R. t. pollicaris Ridgway, 1884: North Pacific Ocean, from high Arctic to temperate north coasts, from the northeast New Siberian Islands to Sakhalin, Kamchatka Peninsula, Kuril and Commander Islands (east Russia), the Aleutian Islands and Bering Sea islands, and west and southwest Alaska mainland. Hind toe (as the name pollex, meaning thumb, suggests) present. Apart from the hind toe, the two subspecies are almost identical, R. tridactyla pollicaris is in general slightly larger than R. tridactyla tridactyla.
Distribution and habitat The black-legged kittiwake is a coastal bird of the arctic to subarctic regions of the world.del Hoyo, J; Elliott, A; Sargatal, J (1996). Handbook of the Birds of the World Vol. 3. Barcelona: Lynx Edicions. pp. 622–623. . It can be found all across the northern coasts of the Atlantic, from Canada to Greenland as well as on the Pacific side from Alaska to the coast of Siberia. Black-legged kittiwakes' wintering range extends further south from the St-Lawrence to the southern coast of New Jersey as well as in China, the Sargasso sea and off the coast of west Africa.Pearson, T. Gilbert (1936). Birds of America. New York: Garden City Publishing. pp. 39–40. There are two subspecies of black-legged kittiwake: R. t. tridactyla can be found on the Atlantic coast whereas R. t. pollicaris is found on the Pacific coast.
Out of all the gulls, the kittiwakes are the most pelagic ones, except for perhaps Sabine's gull. Kittiwakes are almost exclusively found at sea with the exception of the breeding period, from May to September, where they can be found nesting on the sheerest sea cliffs. They are rarely found inland, though occasional vagrants can turn up far inland, even in central Asia well over a thousand km from the sea. For the rest of the year, kittiwake spend most of their time on the wing out of sight from the coast.
Description Adult plumage The adult is in length with a wingspan of and a body mass of . It has a white head and body, grey back, grey wings tipped solid black, black legs and a yellow bill. Occasional individuals have pinky-grey to reddish legs, inviting confusion with red-legged kittiwake. The inside of their mouth is also a characteristic feature of the species due to its rich red colour. Such red pigmentation is due to carotenoids pigments and vitamin A which have to be acquired through their diet. Studies show that integument colour is associated with male's reproductive success.Leclaire, Sarah; White, Joël; Arnoux, Emilie; Faivre, Bruno; Vetter, Nathanaël; Hatch, Scott A.; Danchin, Étienne (2011-9). "Integument coloration signals reproductive success, heterozygosity, and antioxidant levels in chick-rearing black-legged kittiwakes". Naturwissenschaften. 98 (9): 773–782. This hypothesis would explain the behaviour of couples greeting each other by opening their mouth and flashing their bright mouth it to their partner while calling.Bent, A. C. (1963). Life histories of North American Gulls and Terns. London: Dover Publication Inc. pp. 36–48. As their Latin name suggests, they only possess three toes since their hind toe is either extremely reduced or completely absent. In winter, the species acquires a dark grey smudge behind the eye and a grey hind-neck collar. The bill also turns a dusky-olive colour.
Kittiwakes are similar to most other gulls in their moulting pattern with one full moult and one partial moult each year. The full moult from summer to winter plumage though is very protracted, beginning as early as late May or June, and continuing through summer until completed by October, or rarely as late as the end of the year. Then in early spring, there is a partial moult (head and body feathers, but not the wing or tail feathers) from winter plumage to summer plumage in March to early April.
Juvenile plumage At fledging, the juveniles differ from the adults in having a black 'W' band across the length of the wings and whiter secondary and primary feathers behind the black 'W', a black hind-neck collar and a black terminal band on the tail. They can also be identified due to their solid black bill. This plumage is a hatch-year plumage and will only remain for their first year. Kittiwakes obtain their mature plumage at 4 years old, but will gradually change their juvenile plumage over time until maturity is reached. A second-year juvenile resembles a hatch-year regarding the plumage, though the bill is no longer solid black but instead has a greenish colour. The black marking on the coverts and the tail is still visible. The black marking will only moult during their third year, where the black is no longer present on the coverts, but the grey smudge on the head remains. A third-year bird will also exhibit a small zone of bright yellow/orange at the base of its mostly greenish bill. It is only at four years old that the bill will reach an overall colour of bright yellow and complete its mature plumage.Pennington, M.G.; Bainbridge, I.P.; Fearon, P. (1994-04). "Biometrics and primary moult of non-breeding Kittiwakes Rissa tridactyla in Liverpool Bay, England". Ringing & Migration 15 (1): 33–39.
The old fisherman's name of "tarrock" for juvenile kittiwakes is still occasionally used. Standard measurements length weight wingspan wing tail culmen tarsus
Calls
The kittiwake is named after its call that resembles a long "kit-ti-wake". Apart from their typical call, kittiwakes have a wide array of calls. Their greeting call is used by the two members of a pair when meeting at the nest after an absence of one or both members. Before and during copulation, the female will often call by making a series of short high pitched "squeak". This call is also used by the female to beg for food from the male (courtship feeding). When predators are around, the kittiwake alarm call, an "oh oh oh oh" will be heard all across the colony.Hatch, S. A., G. J. Robertson, and P. H. Baird (2009). Black-legged Kittiwake (Rissa tridactyla), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. Kittiwake will call all day for various reasons and will only stop when the sun is down.
Similar species The red-legged kittiwake is the only other species in the genus Rissa and can be differentiated from its counterpart by its red legs, as the name suggests. The head of the red-legged kittiwake is slightly smaller and bears a shorter bill. The chicks of the Pacific black-legged kittiwake and red-legged kittiwake cannot be distinguished during their youngest downy phase.Bent, A. C. (1963). Life Histories of North American Gulls and Terns. London: Dover Publications Inc. pp. 49–51.
Juvenile black-legged kittiwakes can be confused with juvenile little gull and both juvenile and adult Sabine's gull, although the kittiwakes' plumage has broader black 'W' on the wing, the primaries and a different pattern going across the coverts.
Behaviour and ecology Flight Kittiwake are known for their graceful flight. Unlike larger gulls, their flight is light with the wings beating in fast strokes. When looking at them flying around the colony, kittiwakes often look as if they are playing in the wind with their agile flips and loops. Kittiwakes are highly gregarious and therefore are rarely seen flying alone far away from the colony.
Breeding
It is a coastal breeding bird around the north Pacific and north Atlantic oceans, found most commonly in North America and Europe. Kittiwakes are colonial nesters that form monogamous pairs and exhibit biparental care, meaning that both take part in nest building, incubation and chick rearing. They tend to nest in large numbers on cliffs by the sea side. It breeds in large colonies on cliffs and is very noisy on the breeding ground. Cliff nesting for gulls occurs only in the Rissa species, and the kittiwake is capable of utilizing the very sheerest of vertical cliffs, as is evident in their nesting sites on Staple Island in the outer Farne Islands.
Black-legged kittiwake gulls traditionally preferred nesting on natural cliffs and ledges, and there are historically few instances of kittiwakes nesting on man-made structures. The first nesting on buildings on the River Tyne in Northumberland, England, began in 1949 at North Shields and then colonised further upstream, with nesting on buildings in central Newcastle upon Tyne and Gateshead from the early 1960s; by 2020, 1,639 pairs were nesting on buildings along the Tyne (of which 879 pairs on the iconic Tyne Bridge in the heart of Newcastle), with the furthest inland 17 km upriver from the sea. In recent years, some have even been nesting successfully on top of street lights on Newcastle's Quayside. A shift in nesting behaviour has also been noted in the coastal areas of Northern Norway.
Nesting