The Stilt Sandpiper breeds exclusively in low-arctic and subarctic areas of North America and winters mainly in the interior of central South America. This medium-sized wader was once considered the unique extant representative of the genus Micropalama, which was characterized by having exceptionally long legs, partly webbed toes, and a long bill with an expanded tip ( Baird et al. 1884 ). However, none of these characters is unique; all are found in other members of the large genus Calidris, where this species is currently classified ( Jehl 1973a , American Ornithologists' Union 1983 ).
The Stilt Sandpiper's breeding behavior is that of a typical monogamous calidridine sandpiper. Ecologically, however, it differs from most congeners in that it avoids tidal mudflats in favor of pools or lagoons, where it forages in belly-deep water.
Although described as distinctive early in the nineteenth century (“it cannot even at first sight be mistaken for any other Tringa"; Bonaparte 1826 : 57), the Stilt Sandpiper remained largely unknown to ornithologists or even to gunners, who called it the Bastard Yellowlegs because of its suspected intermediacy, or perhaps hybrid origin, between dowitchers (Limnodromus spp.) and yellowlegs (Tringa spp.). Other 19th-century gunning names included Stilted Sandpiper, Mongrel, Long-legged Sandpiper, and Frost Snipe.
Despite having a broad, though probably interrupted, breeding distribution, which extends westward and northward from James Bay (55°N) nearly to Barrow, AK (71°N), the Stilt Sandpiper is not a common species. Accordingly, its breeding biology has been studied in detail at only a few localities: Churchill, Manitoba ( Farley 1936 , Sutton 1961 , Jehl Jehl 1970b , Jehl 1973a ); Victoria Island, Northwest Territories ( Parmelee et al. 1967 ); and Prudhoe Bay, AK (JK). Except for studies by Alexander and Gratto-Trevor ( Alexander and Gratto-Trevor 1997 ) in Saskatechewan and by S. Skagen (unpubl.) in the Great Plains, information on its biology during migration and in winter is sparse.
In spring, this sandpiper's main migration route brings it northward through northern-central South America, across the Great Plains and western Prairie Provinces, to arctic Canada and Alaska. Its fall migration has several pulses, beginning in early July with adult females, followed later by adult males, and finally by juveniles. Its main southward route also passes through mid-continent, west of the Mississippi River. Quill Lakes in Saskatchewan ( Alexander and Gratto-Trevor 1997 ) and Cheyenne Bottoms in Kansas (International Shorebird Surveys [ISS]) are major concentration points both in spring and in fall. From there, in fall the species migrates over water to the Caribbean (Cuba, Puerto Rico: Wunderle et al. 1989 , Collazo et al. 1995 ) or northern South America (Suriname: Spaans 1978a ), where many birds interrupt their migration to molt flight-feathers before continuing to winter haunts in inland central South America. Small numbers migrate in fall along the mid-Atlantic Coast from Long Island, NY, to Virginia.