Species at Risk

The Red Knot: An Intercontinental Traveler in Decline
by Annette Macek Scherer, U.S. Fish and Wildlife Service

Each May, over 1 million shorebirds stop within the Delaware Bay Region of Delaware and New Jersey to rest and refuel before continuing their annual migration from wintering areas to breeding grounds. The timing of this stopover is no accident. For millennia, the red knot and other migrant bird species have been drawn to the Delaware Bay by the abundance of eggs laid each May by spawning horseshoe crabs.

For the red knot, a small russet-colored shorebird about the size of a robin, the Delaware Bay is a crucial stopover on its 10,000-mile journey from the southern tip of South America to the Canadian Arctic. No other area in the Western Hemisphere harbors as large a horseshoe crab breeding population as the Delaware Bay. Feeding on horseshoe crab eggs provides red knots with a fat-rich food source, allowing the birds to double their body weight in as little as 2 to 3 weeks. This weight gain is critical if the birds are to complete migration and successfully breed in the Arctic. With the Arctic winter barely over when red knots arrive, availability of food resources depends on the degree of snowmelt, and knots may have to live off fat reserves for the first week or so of the short Arctic-nesting season.

Over the past 10 years, heavy commercial harvest of horseshoe crabs for conch and eel bait has caused a rapid decline in the crab’s breeding population in Delaware Bay, reducing the number of eggs available to shorebirds. During this same period, the red knot population has suffered severe decline, from over 90,000 birds counted on Delaware Bay in 1989 to 32,000 in 2002. Population estimates of red knots on South American wintering grounds show similar declines, from 67,500 birds recorded during the early 1980s to just over 27,000 red knots counted in 2002.

While the decline in horseshoe crabs is likely a major factor in the decline of red knots, biologists must also look at threats that may affect the species on breeding and wintering grounds. Until recently, little was known about red knots at their remote Arctic breeding grounds. In July 2000, using radio telemetry, an international team of scientists successfully tracked red knots from Delaware Bay to Arctic nesting areas. Since then, studies have been underway to learn more about the species’ breeding biology and habitat, filling in information gaps about breeding density, nest-site characteristics, and productivity. Scientists also are learning more about the impacts of predation and weather on red knot nesting success. In South American wintering areas, researchers are continuing aerial surveys to assess the size of wintering populations and trapping efforts to estimate the proportion of adults to young in the wintering population.

Through international partnerships, biologists are slowly piecing together the life history of this diminutive intercontinental traveler. Without a better understanding of its survival needs, the red knot population could continue to decline—but we are not going to let that happen on our watch.

For more information, contact Annette Macek Scherer, U.S. Fish and Wildlife Service, New Jersey Field Office, 927 N. Main Street, Pleasantville, New Jersey 08232, (609) 646-9310, annette_scherer@fws.gov, or Larry Niles, New Jersey Division of Fish and Wildlife, Endangered and Nongame Species Program, P.O. Box 400, Trenton, New Jersey 08625-0400, (609) 292-9400, larry.niles@dep.state.nj.us.