|
Red Knot Calidris canutus Playero Gordo
|
 |
|
Breeding plumage - Photo:
G. Beaton
|
|
Red Knot Calidris canutus Playero Gordo
|
|
|
Breeding plumage - Photo:
G. Beaton
|
|
IDENTIFICATION: In breeding plumage this species has bright, chestnut-colored undersides. In non-breeding plumage it has gray upperparts, and is white below. It has a white rump with gray barring that is visible in flight and has a "chunky" appearance, hence the Spanish name. Length: 23-25 cm.; weight: 85-220 g. VOICE: Usually silent on migration except for faint contact notes. Audio (M. Oberle). HABITAT: Beaches and wetlands. HABITS: The Red Knot has a complicated foraging strategy that works best in wet sand and shallow pools. As the Knot probes the sand, its bill generates mechanical waves in the wet sand or mud. Sensitive nerve organs called Herbst corpuscles---located in pits at the tip of the bill---pick up reflections and pressure changes in the wet sand and can detect the presence of tiny, buried molluscs and crustaceans. Thus the bird does not have to physically touch a food item to detect potential prey. On the breeding grounds in North America it builds a nest on a grass mound near water. Both sexes incubate the 4 eggs for 21-23 days. The chicks leave the nest soon after hatching and both sexes lead the chicks to foraging areas. But the female abandons the chicks before the young fledge at 18-20 days after hatching. Does not breed until 2-3 years old. STATUS AND CONSERVATION: An uncommon migrant in Puerto Rico in the fall and spring. It was once the commonest North American sandpiper, but populations were decimated by hunting. About 80% of the North American breeding population stops at Delaware Bay to fatten up during spring migration. There they depend on eggs laid by horseshoe crabs (Limulus polyphemus), but the crab population is now threatened by overharvesting for bait. RANGE: Breeds in the Old World and on the Arctic tundra of Alaska, Canada and Greenland. In the autumn migration, most birds fly non-stop from North America to winter grounds in coastal South America. TAXONOMY: CHARADRIIFORMES; SCOLOPACIDAE; Scolopacinae |
 |
|
Non-breeding plumage - Photo: G. Beaton
|
 |
|
Horseshoe Crab (Limulus polyphemus) |
|
References Bent, A.C. 1927. Life histories of North American shore birds, part 1. Smithsonian Instit. U.S. National Museum Bull. 142. (Reprinted by Dover Press, NY, 1962). Borowik, O. A. and D. A. McLennan. 1999. Phylogenetic patterns of parental care in calidridine sandpipers. Auk 116(4):1107-1117. del Hoyo, J., A. Elliott, and J. Sargatal, eds. 1996. Handbook of Birds of the World, Vol. 3. Hoatzin to Auks. Lynx Edicions, Barcelona. Harrington, B. A. 2001. Red Knot (Calidris canutus). No. 563 in The birds of North America (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. Hayman, P., J. Marchant, and T. Prater. 1986. Shorebirds: an identification guide. Houghton Mifflin, Boston. Paulson, D. 1993. Shorebirds of the Pacific Northwest. Univ Washington, Seattle. http://www.state.nj.us/dep/fgw/ensp/about2k.htm Next related species in taxonomic order Previous related species in taxonomic order |