“One flock of about 20 birds was found at Cold Bay. . . . They were found as usual huddled closely together on a slippery, spray-washed rock, apparently oblivious of everything, and showing no particular interest in life.”
Osgood 1904 : Biological reconnaissance of the base of the Alaska Peninsula, North American Fauna
Osgood's anthropomorphic view of Rock Sandpipers in Alaska in mid- October is typical of many who have experienced this species at that time of year. Whether observed foraging on surf-splashed shores, huddled together during a blizzard awaiting low tide, or residing for months on substrates that regularly freeze, the Rock Sandpiper defies most conceptions about shorebirds. Not only does it winter farther north than any North American shorebird, but its pagophilic adaptations are unique among all shorebirds during the nonbreeding season.
This small but stocky sandpiper is truly a bird of Beringia, where at least 4 recognized subspecies have evolved within the region. Each has a distinct breeding plumage, but only one a unique winter dress. The total population of the species likely does not exceed 100,000 individuals; some subspecific populations are limited to several thousand birds and confined to a few islands in the central Bering Sea. The Rock Sandpiper favors low-elevation heath tundra for breeding, but it can also be found nesting at higher elevations throughout coastal mountains of western Alaska. It has a territorial, socially monogamous mating system and, in noninsular populations, often occupies habitat with Black-bellied Plovers (Pluvialis squatarola), Western Sandpipers (Calidris mauri), Dunlin (C.alpina), Ruddy Turnstones (Arenariainterpres), and Bar-tailed Godwits (Limosalapponica). During the short breeding season, the Rock Sandpiper feeds primarily on adult and larval insects on the tundra; the remainder of the year, it resides on intertidal areas, where it subsists primarily on invertebrates, especially marine clams and snails. In autumn, it is not uncommon to find concentrations of tens of thousands of molting birds at single estuaries, especially along the coast of the Yukon Delta and Alaska Peninsula. The species' common name is somewhat of a misnomer, since almost the entire population of one subspecies and large segments of another have recently been found throughout the nonbreeding season on intertidal areas with soft substrates almost devoid of rocks. Migration strategies vary markedly among the various subspecies: one sedentary population engages in only local seasonal movements, whereas another embarks on annual round-trip flights of up to 9,000 kilometers between Russia and northern California.
For such a geographically restricted species, a fair-sized body of information exists, but it is weighted heavily toward subspecific characteristics, taxonomy, and distribution ( Ridgway 1919 , Conover 1944b , Gabrielson and Lincoln 1959 , Kozlova 1962b , Portenko 1981 , Kessel 1989 , Paulson 1993 ) and less toward aspects of reproductive ecology ( Hanna 1921 ; Kondratiev 1982 ; Tomkovich Tomkovich 1985b , Tomkovich 1994b ) and vocalizations ( Miller et al. 1988a , Miller 1996a ). Autumn staging ecology has been addressed by Gill and Jorgensen ( Gill and Jorgensen 1979 ) and Gill and Handel ( Gill and Handel 1990 ), winter ecology and habitat use by Gill ( Gill 1997b ) and Gill and Tibbitts ( Gill and Tibbitts 1999 ), foods and feeding ecology by Preble and McAtee ( Preble and McAtee 1923a ) and Smith ( Smith 1952b ), regional population status by Buchanan ( Buchanan 1999 ) and Gill and Tibbitts ( Gill and Tibbitts 1999 ), and conservation concerns by Gilland Handel ( Gill and Handel 1981a ), Gill et al. ( Gill et al. 1994 ), Gill ( Gill 1996 ), and Buchanan ( Buchanan 1999 ). Data gaps include much-needed information on population demographics, status and trends of subspecific populations, and movements of subspecific populations during the nonbreeding season.