The researchers are from the Wetlands Institute and Richard Stockton College of New Jersey.
During a two-week expedition to Tierra del Fuego that ended January 18th, they counted fewer than 1,000 red knots.
The robin-sized birds feed on horseshoe crab eggs in the Delaware Bay during their annual springtime migration from the Arctic to South America, a 10,000-mile journey.
New Jersey lists the bird as threatened.
The Department of Environmental Protection recently moved to extend a 2006 moratorium on horseshoe-crab harvesting indefinitely.
Some fishermen argue there is no proof a lack of eggs is causing the red knot population decline.
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Information from: The Press of Atlantic City, http://www.pressofatlanticcity.com