A denizen of the far north, the Eskimo Curlew is known to have bred in at least two locations within Canada's northwest territories. A more widespread breeding range, including a vast swath of northern Alaska and a portion of eastern Siberia, is suspected. The Eskimo Curlew also bred on the Arctic tundra. Prior to its decline, it was probably the most common Arctic summer bird.
The Eskimo Curlew utilizes a variety of habitats throughout the year. In spring, it settles mainly on tallgrass prairies from Texas north across the Midwest. Its summer, its Arctic breeding habitat is a vast region of soggy, treeless tundra, nearly inaccessible to humans. This complicates the search for possible remaining populations, which must be done either by air, or on marginally accessible areas. During fall migration, the Eskimo Curlew relies upon the North Atlantic coast, where it was formerly found in great numbers, foraging in marshes, meadows, fields, sand dunes, and tidal areas. From here, the Eskimo Curlew makes its way to its wintering grounds on wide open, flat, wet, grassy areas in Argentina, similar to its Arctic breeding grounds.
Historic accounts indicate that the Eskimo Curlew has a varied diet throughout its annual cycle. In spring, large flocks gorged on grasshoppers, crickets, and other prairie insects. During fall migration, the species reportedly relied heavily upon coastal berries, particularly crowberry patches along the Labrador coast. The birds also consumed prey such as insects, crabs, and other aquatic invertebrates.
Breeding, since it occurs within North America's least accessible regions, has rarely been observed closely. The Eskimo Curlew's nest sites were described by early ornithologists as crude shallow scrapes lined with down and other nesting material, similar to nests constructed by other curlews. Historic descriptions of the species' breeding behavior are also consistent with the behavior of related species. Both parents brood and care for the chicks, which are able to follow the parents and find their own food soon after hatching. In most curlew species, parental care decreases quickly once the young birds fledge.
The annual migration undertaken by the Eskimo Curlew was known to involve a 20,000-mile round trip. After wintering in southern Argentina and Uruguay, Eskimo Curlews began to move slowly north in February or early March. Most birds crossed the formidable Andes, then flew up the Pacific coast of South America, arriving at staging areas along the Gulf Coast and southern Midwest by May. Moving northward across the prairies in huge flocks, they fed heavily on insects such as the now-extinct Rocky Mountain grasshopper. By June, the birds arrived on the northern tundra.
Following the relatively short breeding season, Eskimo Curlews moved east to the north Atlantic coast, particularly Labrador, where they gorged on crowberries, crabs, and insects in preparation for the long flight back to South America. Once properly fattened, large flocks of Eskimo Curlews embarked on a nonstop, two- to three-day flight over the Atlantic Ocean. Once out over the ocean, most would not see land again until they arrived, weak and starving, on the northern coasts of South America. Here the Eskimo Curlews gorged once again, then worked their way 2,000 miles further south, to wintering grounds at the end of the continent.