New Jersey Field Office
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Rufa Red Knot (Calidris canutus rufa) [proposed threatened]

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Additional Information

Red knot

IN BRIEF

Habitat:
In the U.S., Atlantic and bay beaches and mudflats

Diet:
Clams, mussels, snails, horseshoe crab eggs, other invertebrates

Main Threats:
Shoreline development
Reduced food availability
Disturbance
Climate change

Fun Fact:
The red knot makes one of the longest distance migrations known in the animal kingdom.


Overview

Map of red knot distribution in the US
Red knot range in the U.S.

 

Map of red knot distribution in New Jersey by municipality
Red knot distribution in New Jersey

The red knot was added to the list of Federal candidate species in 2006. A proposed rule to list the rufa supbspecies as threatnened under the Endnagered Species Act was published on September 30, 2013. Red knots are federally protected under the Migratory Bird Treaty Act, and are State-listed as endangered.

At 9 to 10 inches long, the red knot is a large, bulky sandpiper with a short, straight, black bill. During the breeding season, the legs are dark brown to black, and the breast and belly are a characteristic russet color that ranges from salmon-red to brick-red. Males are generally brighter shades of red, with a more distinct line through the eye. When not breeding, both sexes look alike—plain gray above and dirty white below with faint, dark streaking. As with most shorebirds, the long-winged, strong-flying knots fly in groups, sometimes with other species. Red knots feed on invertebrates, especially small clams, mussels, and snails, but also crustaceans, marine worms, and horseshoe crab eggs. On the breeding grounds knots mainly eat insects.

Small numbers of red knots may occur in New Jersey year-round, while large numbers of birds rely on New Jersey's coastal stopover habitats during the spring (mid-May through early June) and fall (late-July through November) migration periods. Smaller numbers of knots may spend all or part of the winter in New Jersey.

The primary wintering areas for the rufa red knot include the southern tip of South America, northern Brazil, the Caribbean, and the southeastern and Gulf coasts of the U.S. The rufa red knot breeds in the tundra of the central Canadian Arctic. Some of these robin-sized shorebirds fly more than 9,300 miles from south to north every spring and reverse the trip every autumn, making the rufa red knot one of the longest-distance migrating animals. Migrating red knots can complete non-stop flights of 1,500 miles or more, converging on critical stopover areas to rest and refuel along the way. Large flocks of red knots arrive at stopover areas along the Delaware Bay and New Jersey's Atlantic coast each spring, with many of the birds having flown directly from northern Brazil. The spring migration is timed to coincide with the spawning season for the horseshoe crab (Limulus polyphemus). Horseshoe crab eggs provide a rich, easily digestible food source for migrating birds. Mussel beds on New Jersey's southern Atlantic coast are also an important food source for migrating knots. Birds arrive at stopover areas with depleted energy reserves and must quickly rebuild their body fat to complete their migration to Arctic breeding areas. During their brief 10 to 14-day spring stay in the mid-Atlantic, red knots can nearly double their body weight.

Threats to the red knot include sea level rise; coastal development; shoreline stabilization; dredging; reduced food availability at stopover areas; disturbance by vehicles, people, dogs, aircraft, and boats; and climate change.

Distribution

Species Range: Winter: Chile, Argentina, Brazil, Carribbean, U.S. coasts from Texas to North Carolina with smaller numbers north along the Atlantic as far as southern Canada. Breeding: central Canadian Arctic from northern Hudson Bay to the southern Queen Elizabeth Islands. Migration: Atlantic and Gulf coasts of South America, the U.S., and Canada; the Caribbean; interior flyways across South America; interior flyways across the U.S. and Canada west as far as Alberta (Canada), Montanna, Wyoming, Colorado, and Texas.

Distribution in New Jersey: Transient red knots may be found anywhere along New Jersey's coasts in nearly every month, and may move over inland areas during migration. Large numbers of migrating birds are known to use stopover habitats in Cumberland, Cape May, and Atlantic Counties.




Last updated: January 28, 2014
New Jersey Field Office
Northeast Region Ecological Services
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