Calidris canutus rufa

Nests in Arctic, winters mainly in southern South America; drastic decline in recent decades; population size now in the low 10,000s; overharvest and population declines of horseshoe crabs (the eggs of which are a critical food resource) probably major reason for red knot decline.

Nesting range evidently centers in Canada north of the Arctic Circle in the northern district of Keewatin and in middle-arctic islands of southern district of Franklin, mostly west of 85º and east of 110ºW, including Southampton Island (Godfrey 1992, Harrington 2001). Range during the boreal winter primarily is in southern South America, where the species appears to be most abundant south of 40°S, especially in northeastern Tierra del Fuego, but also numbering in low thousands near equatorial coastlines of Brazil (unclear whether these are subspecies rufa or roselaari) (Morrison and Ross 1989, Harrington 2001). January surveys by Morrison and Ross (1989) indicate that a high proportion of the rufa population spends the boreal winter season concentrated in a single bay, Bahía Lomas in Chile, near eastern end of Strait of Magellan (52º30'S; 69º00'W).

From the perspective of migration, this subspecies could be regarded as having only one or few major occurrences, since most of the population migrates through Delaware Bay (Morrison et al. 2004) and most of the population spends the boreal winter in a small area of Tierra del Fuego (Niles et al. 2007).

Increased commercial harvest of horseshoe crabs (for use as bait in eel and conch fisheries; especially in the Delaware Bay region in the 1990s; Walls et al. 2002, Morrison et al. 2004, Niles et al. 2007), a reduction in horseshoe crab populations, and a consequent reduction in red knot food resources (horseshoe crab eggs), body condition during spring migration, and annual survival (Baker et al. 2004) are the major threats (Gonz lez et al. 2006, Niles et al. 2007). Most of the rufa population migrates through Delaware Bay during northward migration (Morrsion et al. 2004).

Actions to conserve horseshoe crabs have included reduced harvest quotas, more efficient use of crabs as bait, closure of the harvest in certain seasons and places, and the designation of a sanctuary off the mouth of Delaware Bay (Niles et al. 2007). The latest information is that the crab population may have stabilized, but there is no evidence of recovery (Niles et al. 2007).

It is likely that there are other threats to rufa and that these are the cause of some birds arriving in Delaware Bay late and/or in poor condition (Niles et al. 2007). Possibly the threats involve Bahia Lomas, the main wintering site in Tierra del Fuego; the largest reduction in recent years has occurred there, and northward migration from Bahia Lomas along the Atlantic coast of Argentina has taken place 1-2 weeks later since 2000 (Niles et al. 2007).

Additional threats to flocks in winter habitat or migration stops include oil pollution, disturbance by humans, and habitat loss through reclamation for development (Niles et al. 2007).