The robin-sized Red Knot is a miracle of migration, flying more than 9,000 miles from south to north, then back again.

Red Knot map, NatureServeIt's a long way from Argentina to the North American Arctic. But that's the journey the rufa Red Knot takes each year as it makes its way from wintering to breeding grounds. Of course, a journey of so many miles requires stops. This species is unique for its intimate ties to the Delaware Bay and the life cycle of the primeval-looking horseshoe crab.

Bay, Bird, and Crab

Red Knots and crabs_ Gregory Breese, USFWS

Exhausted Red Knots stop to fatten up on nutritious horseshoe crab eggs before continuing their flight. Photo by Gregory Breese, USFWS

As they fly north each spring, the knots stop along the Delaware Bay to refuel on horseshoe crab eggs—an ancient phenomena precisely timed to coincide with the crabs' annual egg-laying. The exhausted birds fatten up on the nutritious eggs before continuing their flight.

Unfortunately, horseshoe crabs also became popular with fisherman, who began to harvest the crabs for bait in the 1980s.

The Red Knot's Decline

The rufa Red Knot's population has taken a nosedive over the past two decades. Historically, more than 100,000 of the birds stopped at Delaware Bay each spring. By 2004, this number had dropped to little more than 13,000.

In 2011, a count of the main wintering population in South America found remaining numbers had declined by one-third.

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Climate Change: Another Knock

Its numbers are much reduced, and now another threat is growing: climate change. Sea-level rise associated with global warming could eliminate important migratory stopover sites for this species and other shorebirds, such as the Ruddy Turnstone and Semipalmated Sandpiper.

Even if critical habitats are not lost, a changing climate may alter the timing of the birds' arrival or the crabs' egg-laying date. The result: Knots without enough food to successfully complete their migration.

Results for the Red Knot

The rufa Red Knot has been a priority species almost since ABC's beginning. It is included on the 2014 Watch List, and finally, after many years of pushing, was listed by the federal government under the Endangered Species Act in 2014.

Although this listing was an important victory, we continue to press for more conservation action. In particular, we want the federal government to designate “critical habitat” for the species, which will enable better management practices for horseshoe crabs and benefit the bird.

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