During their annual northward migration, red knots stop on the Delaware coast where they feed primarily on the eggs of the horseshoe crab, Limulus polyphemus (Niles et al. 2008). This food resource provides fats and protein essential for the birds' long journey to their arctic breeding grounds. In recent years, Delaware horseshoe crab populations have declined from increased bait fishing pressure, leading to negative impacts on the red knot. See 'Special Status' below. On beaches, the red knot uses its bill to probe the sand for molluscan prey, including periwinkles and coquina clams of the genus Donax (Terres 1980). Birds inhabiting tidal flat and salt marsh ecosystems feed on a variety of items, including: small fishes, marine worms, seeds from seagrasses and marsh plants, and a host of insects (Terres 1980). Predators: Little information is available concerning predators of the red knot. However, it is likely that the small size of the species allows it to be preyed upon by a variety of large organisms, including mammals, alligators and birds of prey.Parasites: Like many other bird species, the red knot acts as a terminal or final host for several parasites acquired from a variety of prey items, including the parasitic worms, Bartolius pierrei (Cremonte 2004), Skrjabinocerca canutus, Viktorocara capillaries, and V. limosae (Diaz et al. 2005).
- Cremonte, F. 2004. Life cycle and geographic distribution of the gymnophallid Bartolius pierrei (Digenea) on the Patagonian coast, Argentina. J. Nat. Hist. 38: 1591-1604.
- Diaz, JI, Cremonte, F, Navone, GT & S Laurenti. 2005. Adults and larvae of Skrjabinocerca canutus n. sp. (Nematoda: Acuariidae) from Calidris canutus rufa (Aves: Scolopacidae) on the southern Southwest Atlantic coast of South America. Syst. Parasitol. 60: 113-123.
- Farrand Jr., J (Ed.). 1983. The Audubon Society Master Guide to Birding Volume 1: Loons to Sandpipers. Alfred A. Knopf. New York. USA. 447 pp.
- Harrington, BA, Hagan, JM & LE Leddy. 1988. Site fidelity and survival differences between two groups of new world red knots (Calidris canutus). The Auk 105: 439-445.
- Kale II, HW & DS Maehr. 1990. Florida's Birds. Pineapple Press. Sarasota, FL. USA. 288 pp.
- Niles, LJ, Sitters, HP, Dey, AD, Atkinson, PW, Baker, AJ, and 17 others. 2008. Status of the Red Knot (Calidris canutus rufa) in the Western Hemisphere. Studies in Avian Biology No. 36. Cooper Ornithological Society. 185 pp.
- Paulson, D. 2005. Shorebirds of North America: A Photographic Guide. Princeton Univ. Press. Princeton, NJ. USA. 361 pp.
- Peterson, RT. 1980. A Field Guide to the Birds: A Completely New Guide to All the Birds of Eastern and Central North America. Houghton Mifflin. Boston, MA. USA. 384 pp.
- Terres, JK. 1980. The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf. New York. USA. 1109 pp.
- USFWS. 2010. The red knot (Calidris canutus rufa). U.S. Fish & Wildlife Service. Online at http://www.fws.gov/northeast/redknot/ (Date accessed 08/12/2010).
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