Despite its ubiquitous appearance as a curio in gift shops, the Horned Puffin is a poorly studied member of the auk family. Distributed throughout subarctic waters of the North Pacific, its large breeding colonies are isolated and difficult to access. Unlike its close relatives, the Atlantic Puffin (Fratercula arctica), Tufted Puffin (F. cirrhata), and Rhinoceros Auklet (Cerorhinca monocerata)—which typically nest in burrows dug into soft soil—the Horned Puffin generally nests in rock crevices and on cliffs, making it difficult to access chicks or adults for routine studies of breeding biology.
Horned Puffins are known for carrying beakfuls of small fish to their young during the breeding season, and one might rightly conclude that they are well suited to living in coastal habitats that teem with abundant forage fish such as sand lance (Ammodytes hexapterus) and capelin (Mallotus villosus). However, this image belies their pelagic diet and ecology. While adults feed mostly fish to their chicks, they themselves consume a substantial proportion of squid and other inverte-brates. During the non-breeding season, adults migrate far south to oceanic waters of the central North Pacific, where diets consist largely of bathypelagic lanternfishes and squid. Juveniles migrate south to the central North Pacific immediately after fledging and may not return to coastal breeding areas for several years. Thus, the Horned Puffin is truly a pelagic species, spending most of its life at great distances from land in the company of species we more typically consider oceanic, such as albatrosses and shearwaters.
Only a handful of studies have focused on Horned Puffins, although much incidental information is available from general seabird field investigations ( Petersen 1983a , Byrd et al. 1993 ). Sealy ( Sealy 1973b ) provided the earliest review of the biology of this species in the North Pacific, with details of breeding ecology on St. Lawrence Island. Soon after, Wehle ( Wehle 1976 , Wehle 1980 ) and Amaral ( Amaral 1977 ) conducted graduate studies on Horned and Tufted puffins, adding a wealth of new information on breeding biology, behavior, chick growth, diets, and habitat use in the Gulf of Alaska and the Aleutians Islands. Since then, only a few studies have added substantially to our knowledge of Horned Puffins (Hatch and Hatch Hatch and Hatch 1990a , Hatch and Hatch 1990b ; Kitaysky 1996 ; Harding 2001 ). For the future, studies of colony attendance behavior would be useful for establishing population monitoring protocols. More data on feeding ecology and breeding biology would be useful for assessing temporal and spatial variability in population biology.