Black-legged Kittiwakes are small, pelagic gulls with a circumpolar distribution in the northern hemisphere. They feed at the ocean surface on fish and macrozooplankton, mostly in daylight, but also at night when foraging over deep ocean waters, where key prey approach the surface in darkness. They breed in colonies numbering from a few to many tens of thousands of pairs.
Kittiwakes are widely studied in both the Atlantic and Pacific portions of their range. The attention stems from their ubiquity and the ease with which they can be observed in their open, sea-cliff nesting habitats. The species figures prominently in seabird monitoring programs mounted since the 1970s in Europe, eastern Canada, Alaska, and Russia.
Even in advance of such latter-day efforts, however, kittiwakes assumed a special place in the annals of ornithology. In 1949 a few pairs began nesting on the window ledges of an abandoned warehouse near the mouth of the river Tyne in North Shields, England. There they attracted the attention of John Coulson, then a graduate student in animal ecology at the University of Durham. Coulson's papers on kittiwake demography, ecology, and behavior, spanning about 40 years of observations from 1950 through 1991, are now classics of animal ecology, and a compelling testament to the importance of long-term studies in avian research (for reviews see Coulson and Thomas Coulson and Thomas 1985a , Wooller et al. 1992 ). The warehouse kittiwakes were evicted eventually to make room for human tenents, but a European tradition of long-term studies continues at the Isle of May in Scotland ( Hatch 1987c , Wanless and Harris 1992 , Daunt et al. 2002 , Frederiksen et al. 2004 ), in Shetland ( Furness 1979 , Heubeck et al. 1987 , Hamer et al. 1993 , Heubeck and Mellor 1994 , Heubeck 2006 ), at Cap Sizun in Brittany, France ( Danchin and Monnat 1992 , Danchin et al. 1998 , Cam et al. 2005 , Naves et al. 2006 ), in Norway and Svalbard ( Barrett and Runde 1980 , Gabrielson et al. 1987 , Bech et al. 1999 , Jacobsen et al. 1995 , Barrett and Bakken 1997 , Moe et al. 2002 ), and indeed at surviving colonies in North Shields ( Coulson and Strowger 1999 , Fairweather and Coulson 1995b ).
In North America, the works of Swartz ( Swartz 1966 ) in Alaska and Maunder and Threlfall ( Maunder and Threlfall 1972 ) in Newfoundland were notable pioneering efforts. The1970s brought environmental threats posed by offshore oil drilling in Canada and Alaska, prompting national governments to undertake extensive biological studies in their respective marine economic zones. Early effort in Canada focused on the Arctic ( Nettleship 1977b , Bradstreet 1982a ); more recently, kittiwake research has occurred mainly in Newfoundland and Labrador ( Regehr and Montevecchi 1997 , Hipfner et al. 2000a , Massaro et al. 2000 , Massaro et al. 2001 ). In Alaska, a broad program of studies in the 1970s (Outer Continental Shelf Environmental Assessment Program, or OCSEAP) established many locations where kittiwakes are still monitored today in the Bering and Chukchi seas and Gulf of Alaska. In addition to routine monitoring of productivity and numbers, in-depth studies of kittiwake ecology continue in a few places including Shoup Bay in Prince William Sound ( Irons 1998 , Suryan and Irons 2001 , Ainley et al. 2003 , Golet et al. 2004 ), Middleton Island in the north-central Gulf of Alaska ( Hatch and Hatch 1990b , Roberts and Hatch 1993 , Gill and Hatch 2002 , Jodice et al. 2002 , Lanctot et al. 2003 , Gasparini et al. 2006c , Kempenaers et al. 2007 ), and St. George Island in the Bering Sea ( Hunt et al. 1981e , Braun and Hunt 1983 , Kildaw 1999 , Lance and Roby 1998 , Lance and Roby 2000 ).
A major finding from the Alaska work is that life history traits of Pacific kittiwakes differ strikingly from those reported from the northeast Atlantic (Table 1 ). As a rule, the Atlantic birds are more productive, but have much shorter lives, than Pacific kittiwakes. This situation calls for research into genetic, ecological, and physiological factors responsible for such plasticity ( Hatch et al. 1993b ).
Black-legged Kittiwakes are considered prime indicators of fluctuating conditions in marine systems—both short term, as reflected by annual variation in breeding success, and long term, as indicated by life-history patterns. Fortunately, breeding kittiwakes are remarkably tolerant of disturbance from those who would meddle in their affairs. Accordingly, Black-legged Kittiwakes are affectionately regarded by many ornithologists as the “white rats” of the seabird world.