Habitat

Uses different tundra habitats for nesting and foraging. Most breeding locations are near but not on arctic coasts (Cramp and Simmons 1983), especially on peninsulas or islands. Habitat selection may vary with snow or other conditions when individuals arrive in breeding areas. In most published accounts (Pleske 1928, Parmelee et al. 1967, Nettleship 1974, Portenko 1981), nests were found on dry, sunny, slightly elevated tundra locations, often on windswept ridges or slopes dominated by stunted willow (Salix spp.) and/or dryas (Dryas spp.). In Siberia, most nests are located within 30 km of arctic coast in gently sloped, hilly or low mountain landscapes where moss tundra and marshes of sedge grass are present at middle and lower parts of the slopes (Tomkovich and Soloviev 1996).

Before egg-laying, foraging is sometimes restricted to elevated habitats if lower elevations remain snow-covered. On w.-central Ellesmere I., by contrast, most nests are in wet habitats, sometimes on hummocks just a few centimeters above standing water; few nests are on more elevated slopes and ridges nearby (Parmelee and MacDonald 1960). In Greenland, nests are on high plateaus up to 300 m and rarely lower than 10 m above sea level (Salomonsen 1950).

Like many other kinds of shorebirds, this species uses strikingly different habitats during breeding and nonbreeding seasons. During its first migration a juvenile knot, which may have spent its entire life in nonmarine, arctic habitats, will fly to coastal habitats where it faces a whole new set of foraging options. Nevertheless, individuals must fatten rapidly in preparation for the next leg of the southward migration.

During migration, uses marine habitats in both South and North America, generally preferring sandy coastal habitats at or near tidal inlets or the mouths of bays and estuaries (BAH). All major staging sites of C. c. rufa south of the equator are associated with high wave-energy, ocean- or bay-front habitats (Harrington et al. 1986, Vooren and Chiaradia 1990, Blanco et al. 1992); the same generally holds true in North America, but may not hold true for other races (e.g., C. c. rogersi in the Australasian region). In some cases, beach habitats are preferred because of high densities of benthic bivalves (Harrington 1996), or at some locations specialized habitats such as peat banks or restinga are frequented because of high densities of epifaunal invertebrates such as mussels (Gonzalez et al. 1996). Red Knots also use tidal flats in more sheltered bays or lagoons, where they hunt for benthic invertebrates (Harrington et al. 1986) or for special foods such as horseshoe crab (Limulus) eggs (Harrington 1996, Tsipoura and Burger 1999). Although large numbers of individuals are sometimes recorded at nonmarine sites during migration (Strahlendorf 1980), in most cases these are isolated instances, as may occur when migrants are forced down by inclement weather (Mawby 1984, Jehl 1994).

During the boreal winter, frequents intertidal habitats, especially on coasts of oceans and large bays where relatively high wave or current action supplies sandy habitat (Fig. 2). Typical habitats are similar to those described above for migration (Piersma et al. 1993, Harrington 1996, Tabilo et al. 1996).