Animalia Life

Rissa tridactyla
SUBFAMILY
Larinae
TAXONOMY
Rissa tridactyla Linnaeus, 1758, Great Britain. Two subspecies are recognized.
OTHER COMMON NAMES
English: Kittiwake; French: Mouette tridactyle; German: Dreizehenmцwe; Spanish: Gaviota Tridactyle.
PHYSICAL CHARACTERISTICS
15–16 in (38–40 cm), 0.7–1.1 lb (305–512 g). Small whiteheaded gull with short legs, blue-gray mantle and upperwing coverts, outer wing slightly paler with sharply defined triangular all-black wingtip. Bill yellow and legs blackish. Nonbreeding adult has dusky gray crown band and nape, darker band across hindcrown, and dark mark around eye. Juvenile has black zigzag pattern across upperwings, black nuchal band, and black subterminal tail band.
DISTRIBUTION
R. t. tridactyla: North Atlantic from north-central Canada and northeastern United States through Greenland to western and northern Europe and on to the Taymyr Peninsula and Severnaya Zemlya; winters south to Sargasso Sea and western Africa. R. t. pollicaris: North Pacific from northeast Siberia, Kamchatka, Sea of Okhotsk and Kuril Islands through Bering Sea to Alaska; winters south to East China Sea and northwest Mexico.
HABITAT
Breeds on coasts as far north as open water allows, nesting on high and steep cliffs with very narrow ledges, and on window ledges of buildings or on piers. Remains in arctic and temperate waters during winter; highly pelagic, often far from land along the continental shelf.
BEHAVIOR
Diurnal; known for its cliff-nesting habitat to avoid avian and mammalian predation.
FEEDING ECOLOGY AND DIET
Feeds mainly on marine invertebrates and fish by dipping, surface seizing, and plunge-diving. Recently exploiting garbage, foraging behind fishing vessels and at sewage outfalls. Also will scavenge and eat earthworms, small mammals, and even vegetation (grain, aquatic plants, potatoes).
REPRODUCTIVE BIOLOGY
May occupy colonies as early as January or February, often waiting for snow to melt from its northern nesting cliff ledges. Nests in mixed-species colonies, and monospecifically, of 10,000 kittiwakes or more. Courtship occurs on the ledges. Lays two eggs. Both sexes incubate the eggs and care for the young. Incubation 24–28 days. Fledging period 35–40 days. First breeds at four years of age.
CONSERVATION STATUS
Not globally threatened. Abundant and has generally increased and expanded into new breeding and foraging locations. Colonies can be threatened by overexploitation of eggs and by oil spills on foraging grounds. Slaughtered for the millinery trade in the late 1800s. Meat eaten by some peoples.
SIGNIFICANCE TO HUMANS
Kittiwakes are still egged in many of their northern colonies. In some places, sections of colonies are “owned” by individuals who egg them for sustained yield over many years.

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