The red knot is a migratory shorebird about the size of a mourning dove. A bright salmon face and breast against a spangled black-and-white back give this shorebird an overall pinkish look from a distance.

Each spring, red knots migrate from wintering areas as far south as Tierra del Fuego, at the southern tip of South America, to breeding grounds in the Canadian Arctic – a 20,000 mile round trip. The red knot is one of our longest-distance migrants spending over 6½ months of the year migrating back and forth between wintering and breeding areas.

The Delaware Bay is the linchpin of the red knot’s spring migration because it is the center of the Western Hemisphere’s only population of horseshoe crabs. Horseshoe crab eggs, unlike any other food resource, are quickly metabolized into fat that allows red knots and other shorebirds to double their body weight in a brief period – about two to three weeks. 

This weight gain is critical for survival because Delaware Bay is the last stop before red knots reach still-frozen arctic breeding grounds, where it takes one to three weeks for insect food to become available.  The fat reserves, put on in Delaware Bay, allow red knots to survive and continue courtship, mating and egg laying until food becomes available.  Without a sufficient fat reserve, the consequence is loss of reproduction, or worse, mortality.

Although commercial horseshoe crab landings were poorly documented prior to the late 1990s, it is recognized that with the significant expansion of the conch pot fishery in the mid-Atlantic region, the demands for horseshoe crabs as bait further stressed the resource when added to the already existing bait demands for horseshoe crabs, particularly females, for the American eel fisheries.  New Jersey was one of the first Atlantic coastal states to implement a state-specific horseshoe crab-permitting and harvest-reporting system in 1993. New Jersey horseshoe crab reported landings increased tremendously from 1993-1997, when it became necessary to implement limited entry , a ban on mobile gear in harvesting horseshoe crabs, and additional area and seasonal closures to reverse the increasing exploitation of the horseshoe crab resource. The implementation of an Atlantic coast-wide fishery management plan by the Atlantic States Marine Fisheries Commission in 1999 was effective in documenting and reducing the horseshoe crab commercial harvest for all states from Maine through Florida over the last decade. While there is evidence of increasing numbers of juvenile horseshoe crabs within recent years, the harvesting pressure on the spawning stock had not only impacted the sexually mature segment of the horseshoe crab population but reduced the abundance of horseshoe crab eggs available to feed the migratory shorebirds utilizing Delaware Bay beaches during the spring.

As the number of horshoe crabs necessary to supply sufficient eggs to meet the needs of migratory shorebirds declined, so did the red knot population.

While the red knot is most imperiled, most studied shorebord on the Delaware Bay, there are five other species that rely on crab eggs and whose populations have declined on Delaware Bay by about 65 percent: Ruddy turnstone (Arenaria interpres), sanderling (Calidris alba), semipalmated sandpiper (Calidris pusilla), dunlin (Calidris alpina) and the short-billed dowitcher (Limnodromus griseus).

Gaining Weight for the Trip

There is a dramatic difference in weight from when a red knot arrives on the Delaware Bayshore and when it's ready to depart for the Arctic.

Red knot upon arrival - 90 grams

Red knot ready to depart - 200 grams