Two subspecies (possibly representing distinct species, see discussion below):
Rissa tridactyla tridactyla
- Atlantic Black-legged Kittiwake
Rissa tridactyla pollicaris - Pacific Black-legged Kittiwake
Between Common Black-headed Gull and Mew Gull in size. The tail shows a slight fork but this is often difficult to discern in the field. Very short legged and stands with an awkward upright posture. Most similar to the closely-related Red-legged Kittiwake and to Sabine's Gull. Has three major age groups; juvenile, 1st year and adult, although 2nd year birds are identifiable at close range. Peter Grant (1993) provides an excellent plumage account together with representative photographs of all ages. Unfortunately, he focuses exclusively on the Atlantic form (see below).
Juvenile: (July to September) Have a very striking black 'W' pattern that offsets the white inner primaries and outer secondaries. Neat black band across the tips of the tail feathers. Has a strongly marked black half-collar on the lower hindneck, a crescent-like smudge over the ear coverts and discrete black spot above the rear half of the eye. The bill is black.
Rissa tridactyla pollicaris. The Aleutians, Alaska in June. Photograph copyright of Angus Wilson©.
First Year: (August to April) Similar to juvenile plumage, except that it develops a pale gray wash over the rear crown and hindneck, creating a weak hooded effect. The black half-collar is reduced and become dark gray rather than black. Carpal bar also fades but is still obvious. Very rarely (0.1% or less) shows no visible carpal bar separating the white and gray areas of the upperwing, thus resembling Sabine's Gull. Bill develops some green-yellow coloration. By first summer, patterning becomes very worn and faded. Molts head and body feathers as well as some of the inner wing coverts. The black terminal tail band becomes very worn by abrasion. Bill now extensively yellow or greenish-yellow.
Rissa tridactyla pollicaris. Honshu, Japan in January. Photograph copyright of Angus Wilson©.
Adult: Solid black wings tips lacking mirrors or white primary tips. Uppersurface of the inner wing and the mantle are a dark neutral gray. The outer wing (particularly the bases of the primaries) is slightly lighter creating a two-toned effect that is very useful in identifying birds at a distance. The bill is relatively slender and a dull lemon yellow, generally without additional markings. The legs are dark brown or black (occasionally other colors). In alternate plumage, the head is immaculate white whereas in basic plumage the develops a dark gray smudge across the hind collar and an even darker spot over the ear coverts. There is also variable smudging above the eye. Birds in breeding condition develop a orange-red or red orbital ring which offsets the beautiful dark brown iris. Some birds have a whitish tip to the bill. The mouth and gape is orange.
Second year: Resemble adults but retain dark fringing to the outermost primaries and primary coverts, some uneven black markings on the bill and the dark head/neck smudging during the summer months. Very rarely shows some dark marks on the tail.
Flies with leisurely wing beats in calm weather switching to more powerful strokes in higher winds. Under such conditions the wings are pulled back and are more bent at the carpal. In very winds will shear much like a fulmar. Kittiwakes are adept marine scavengers, picking fishing debris and galley scraps from the surface of the water.
Separation of Pacific and Atlantic
Black-legged Kittiwakes: Although the modern gull literature tends
to view Black-legged Kittiwake as a relatively uniform and easy to identify
species, it has long been recognized (e.g. Chapman, 1899) that Kittiwakes
come in two flavours; the Atlantic and Pacific Black-legged Kittiwake.
Writing in 1925, Jonathan Dwight, the founding father of gull identification,
described a number of useful distinctions: Pacific birds are larger (especially
the bill) and have a slightly darker mantle. Differences in the patterning
of black in the adult primaries is probably the most useful feature for
subspecific identification in the field (or photographs, see examples below).
In most Atlantic Kittiwakes, only the five longest primaries (P10-P6) show
black tips, whereas in birds from the Pacific P5 is frequently also black
tipped. The extent of black on each feather is also greater on Pacific
birds. Measuring the extent of black along the feather shaft, Dwight records
an average of 64.3 mm (n=23, range 54-75 mm) for Atlantic birds and 72.9
mm (n=28, range 64-92) for Pacific birds. In addition, Dwight noted that
the presence of a hindtoe was more frequent in specimens from the Pacific
(about 50% of individuals) compared to those from the Atlantic (about 9%).
Clearly the presence or absence of a hindtoe is of limited use in the identification
of individual birds, but does support the existance of separate populations.
Where and When
Black-legged Kittiwakes have a circumpolar breeding distribution reaching as far north as open water permits. Prefers high and steep cliffs with narrow ledges. Occasionally nests on snowbanks and glaciers. In Europe has begun to nests on buildings and other man made structures with increasing frequency.
Atlantic Black-legged Kittiwakes (R. t. tridactyla) breed along the coasts of northern and central arctic Canada, Greenland, Iceland, western and northern Europe and the Russian arctic as far east as the Taimyr Peninsula and Severnaya Zemlya. Non-breeders wander widely in the North Atlantic reaching the coasts of west Africa.
Pacific Black-legged Kittiwakes (R. t. pollicaris) breed along the coasts of northeastern Siberia, Kamchatka, the Sea of Okhotsk, the Kurile Islands, and throughout the Bering Sea as far as mainland Alaska. Non-breeders wandering south through the Japanese archipelago to the East China Sea and Baja California.
Rissa tridactyla tridactyla. Adult in alternate plumage, gliding on an updraft at a breeding site. Notice the number of black tipped primaries. Photographed in Scotland. Image copyright of Jeremy Barker©.
Photographs on the web
Pacific Black-legged Kittiwake:
Basic-plumaged adult Pacific Black-legged Kittiwake in flight Taken in Alaska. Photo by Monte Taylor.
Pacific Black-legged Kittiwake in flight Taken off California. Photo
by Monte Taylor.
Atlantic Black-legged Kittiwake:
Superb photo of an adult-basic Atlantic Black-legged Kittiwake in flight. Notice the distribution of black on the primary tips. Taken by Brian Patteson in February.
Another superb flight shot of an adult-basic Atlantic Black-legged Kittiwake. Taken by Brian Patteson in December.
Ventral view of an adult-basic Atlantic Black-legged Kittiwake. Taken by Brian Patteson in Feb.
nesting adult Atlantic Black-legged Kittiwakes? Photo on the Birds
of Foula web site, and thus presumably from the North Atlantic.
Chapman, F.M. (1899) Report on birds recieved through the Peary expeditions to Greenland. Bulletin American Museum of Natural History. Vol 13: p225-229.
Dwight, J. (1925) The Gulls (Laridae) of the World; their plumages, moults, variations, relationships and distribution. Bulletin American Museum of Natural History. Vol 52: p63-408.
Grant, P.J. (1986) Gulls: A guide to identification. 2nd edition. Academic Press.
Szantyr, M. (1998) Black-legged Kittiwake at a distance. Connecticut Warbler 18: 146-147