Kittiwakes
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The Kittiwakes (genus Rissa) are two closely related seabird species in the gull family Laridae.
The more common and widespread species, Rissa tridactyla, is known in North America as Black-legged Kittiwake (or more colloquially in some areas as Tickleass or Tickleace), but in Europe, where it is the only member of the genus, it is often known just as Kittiwake.
Adults are roughly 40 cm (16 in) in length with a wingspan of 90–100 cm. They have a white head and body, grey back, grey wings tipped solid black, and have black legs and a yellow bill. Occasional individuals have pinky-grey to reddish legs, inviting easy confusion with Red-legged Kittiwake. In winter, they acquire a dark grey smudge behind the eye and a grey hind-neck collar. The name is derived from its call, a shrill 'kittee-wa-aaake, kitte-wa-aaake'.
It is a coastal breeding bird around the north Pacific and north Atlantic oceans, found most commonly in North America and Europe. 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. Kittiwakes are capable of utilizing the very sheerest of vertical cliffs, as is evident in their nesting sites on Staple Island in the outer Farne Islands (Hogan, 2005). One to two buff spotted eggs are laid in the nest lined with moss or seaweed. The downy young of Kittiwakes are white, since they have no need of camouflage from predators, and do not wander from the nest like Larus gulls for obvious safety reasons.
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. The old fishermans' name of "tarrock" for juvenile Kittiwakes is still occasionally used.
They are fish feeders, and are more pelagic than Larus gulls outside the breeding season. They do not scavenge at tips like some other gull species.
There are two races of Black-legged Kittiwake:
- Rissa tridactyla tridactyla in the North Atlantic Ocean, which is unique among the Laridae in having only a very small or even no hind toe.
- Rissa tridactyla pollicaris in the North Pacific Ocean, which (as the name pollex, thumb, suggests) has a normally developed hind toe.
The Red-legged Kittiwake (Rissa brevirostris) is a very localised subarctic Pacific species. Apart from the distinguishing feature implicit in its name, it is very similar to its better known relative; other differences include the shorter bill and darker grey wings, and in the juveniles, which barely differ from the adults, lacking the black tail band and 'W' across the wings of juvenile Black-legged Kittiwakes.
Like the Pacific race of Black-legged Kittiwake, the Red-legged Kittiwake has a well-developed hind toe. As occasional individual Black-legged Kittiwakes have reddish legs, any reports of Red-legged away from the subarctic Pacific must record all of the other differences, not just the leg colour, for acceptance by bird recording authorities.
Copyright: Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia.org
- Black-legged Kittiwake: USGS ... New England Seabirds
- Red-legged Kittiwake: USGS
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