Biologists led by the New Jersey Department of Environmental Protection have been monitoring the bird for the last 23 years amid signs that it may soon join the dodo on the list of birds never to be seen again.

After a monthlong ground and air search of the beaches of Delaware Bay in New Jersey and Delaware, scientists this week concluded that the red knot's population is now even closer to the level where it may not survive. They consider the population would be sustainable at about 100,000.

The 10-inch-long bird with a rusty red breast and mottled gray back could be extinct by 2010 or shortly thereafter if its Arctic breeding is disrupted by bad weather or by attacks from predators, undermining the ability of the perilously small population to regenerate, said Larry Niles, former head of New Jersey's endangered species program and the leader of the annual red knot count.

"Because the population is so low, it's vulnerable to a lot of other things," Niles said.

The red knot's numbers have been decimated by overharvesting of horseshoe crabs, whose eggs are its staple diet. With enough food, the 4.7-ounce (135-gram) bird can put on sufficient weight to complete its 9,000-mile (14,500-km) migration from southern Argentina to Arctic Canada each spring, and will hopefully breed successfully when it gets there.

The crabs, used mostly as bait by conch fishermen, have been removed by the thousands from the bay beaches that are a crucial refueling stop on its epic migration. Despite a two-year moratorium on harvesting them on the New Jersey side of the bay, the number of crab eggs is down by a third from last year, Niles said.

Even if the crab harvest is banned indefinitely throughout Delaware Bay, it will take a decade or more for its population to recover to the point where it can feed increasing numbers of knot because the crabs take nine years to reach sexual maturity.

ENDANGERED SPECIES LIST?

The bright spot in this year's count was that captured birds were found to be of a healthy weight, suggesting that for now there are enough crab eggs to feed a dwindling population.

Niles urged New Jersey to extend the moratorium when it expires later this year and called on the federal government to add the bird to its endangered species list. In Delaware, officials have proposed banning the crab harvest but that is being challenged in court by fishing interests.

Concern over the bird's fate draws ornithologists to the annual count. This year they came from New Zealand, Australia, Canada, Britain and Mexico.

Clive Minton, a shorebird specialist from Melbourne, Australia, has been coming to the New Jersey beaches each year since 1996 to contribute his expertise.