The Red Knot is a migratory shorebird that breeds on the elevated tundra of central Canada before migrating each fall to multiple wintering grounds on the coasts of North and South America. The Rufa Red Knot subspecies has been designated as federally threatened species under the ESA. The overwintering grounds for the Rufa subspecies include portions of the northwestern Texas Gulf Coast near the mouth of the Guadalupe River Basin and San Antonio Bay estuary (Newstead 2014). The USFWS has identified several threats to this species due to the destruction and modification of overwintering habitat as a result of climate change, shoreline stabilization, and coastal development as well diminished food supply on the Atlantic coast migratory pathway due to commercial harvesting of horseshoe crabs (USFWS 2014; Escudero 2012).
Calidris canutus rufa
USFWS Endangered Species Act Status:
TPWD Species Conservation Status:
Aransas, Calhoun, and Refugio counties
The Red Knot is a medium-sized shorebird with a brick red plumage on the face, breast, upper belly and on a stripe above the eye. The lower belly is colored white with dark flecks and the back and outer feathers are dark brown to black. The short legs are dark gray to black. Males and females have similar coloring, but the female coloring may be more muted (Harrington 2001).
The Red Knots lifespan is typically at least seven years long and they begin breeding at the age of two. The knots form groups of breeding pairs upon arrival at the High Arctic nesting grounds in late May or June, which stay together through the hatching of eggs (Niles 2008; Harrington 2001). The females begin migrating south in mid-July, soon after the eggs hatch, while the males provide care for the foraging before beginning their own migration (Niles 2008). The birds migrate through both the Atlantic and Pacific coasts of North and South America, with the Rufa subspecies primarily utilizing the Atlantic coast, before reaching wintering grounds on the coasts of the United States, Mexico, the Caribbean islands and South America. The Knots migrate back to the Canadian breeding grounds in February.
Habitat and Diet:
The Red Knot utilize the tundra shrubland of the Central Canadian High Arctic for their breeding and nesting grounds. The birds’ diet on nesting grounds consists mostly of insects (Niles 2008). Several resource dense, short-term staging locations, with large amounts of easily obtainable food sources such as horseshoe crab in Delaware bay, are utilized during long distance seasonal migrations. Preferred migratory habitats are tidal and marine coastal areas with large spans of intertidal sediments. Wintering habitats are generally in the sandy or muddy areas on tidal flats, tidal inlets and at the mouths of bays and estuaries (Niles 2008; Harrington 2001). Red knots primarily eat hard- and soft-shelled mollusks such as crabs and shrimp in their overwintering habitat.
Escudero, G., Navedo, J.G., Piersma, T., De Goeij, P., and P. Edelaar. (2012). Foraging conditions ‘at the end of the world’ in the context of long-distance migration and population declines in red knots. Austral Ecology 37:355-364.
Harrington, B.A. (2001). Red knot (Calidris canutus). The birds of North America, No. 563, The Birds of North America, Inc., Philadelphia, PA.
Niles, L.J., Sitters, H.P., Dey, A.D., Atkinson, P.W. Baker, A.J., Bennett, K.A. Carmona, R., Clark, K.E., Clark, N.A., Espoz, C., González, P.M., Harrington, B.A., Hernández, D.E., Kalasz, K.S., Lathrop, R.G., Matus, R.N., Minton, C.D.T., Morrison, R.I.G., Peck, M.K., Pitts, W., Robinson, R.A., and Serrano, I., (2008). Status of the red knot (Calidris canutus rufa) in the Western Hemisphere. Studies in Avian Biology 36, 1-185.
United States Fish and Wildlife Service. (2014). Rufa Red Knot Background Information and Threats Assessment. Pleasantville, New Jersey.
United States Fish and Wildlife Service. (2020). Species Status Assessment Report for the Rufa Red Knot (Calidris canutus rufa) Version 1.1. Galloway, New Jersey.