Wednesday, March 31, 2010

Red Knots in New Jersey

Nearly four years after New Jersey banned horseshoe crab harvesting to protect a vanishing shorebird at the Delaware Bay, scientists say they are not optimistic about recent evidence showing the red knots may be on the rebound.

After journeying from the southern tip of South America, red
knots appear on the shores of Delaware Bay in May. They are generally so thin that they look like sparrows. There they will try to gorge themselves on the eggs of the horseshoe crab (Limulus polyphemus) and put on a layer of fat. If successful, they will look more like plump doves when they leave for the Arctic.

Ground surveys at Delaware Bay last spring found 24,000 red knots. That's an improvement from the 15,000 counted in 2008. Biologists also reported increased numbers of crab eggs on the bay estuaries. But neither the horseshoe crabs nor the red knots can be called a "recovered population" and the fate of the birds is linked to the crabs.

Horseshoe crabs are used as bait in the conch and eel industry. NJ fishermen contend that the cottage crab industry was unnecessarily hurt by by imposing a harvesting ban in 2006 that was extended indefinitely by law in 2008.

In an article, biologist Amanda Dey with the New Jersey Endangered and Non-Game Species Program said about last year, "We’ve seen a bump up in the numbers. ... It was a year that we had settled weather, so there were more crabs and more birds. We’d like to think we saw the bottom. But we don’t know."

Dey is part of the team of scientists studying both the crabs and the birds. They traveled to Tierra del Fuego, where they counted about 14,800 red knots in prime South American wintering grounds. The good news is that amount matches winter counts there over the past three years, which suggests that there has not been further declines. Unfortunately, the overall numbers are still at a potential crash level.

Our Delaware Bay spring count last year was still less than half the 50,000 birds recorded there in 1998.

New Jersey has the only moratorium among the 15 coastal states. Neighboring Delaware limits harvests to 100,000, male-only crabs annually.

It would probably surprise many New Jerseyeans that Delaware Bay is at the center of this dispute. It's because the Bay is where the world’s largest population of breeding horseshoe crabs emerges from winter waters each spring to lay eggs on the estuary shores.

Red knots are not the only birds that stop in NJ to bulk up on the eggs as they migrate. But red knots have one of the longest migrations flying from their South American wintering grounds to their Arctic breeding grounds.

More on red knows and NJ at

The Flight of the Red Knot: A Natural History Account of a Small Bird's Annual Migration from the Arctic Circle to the Tip of South America and Back

Red Knot: A Shorebird's Incredible Journey

Horseshoe Crabs and Shorebirds: The Story of a Food Web

Horseshoe Crabs

Horseshoe Crabs (Schaefer, Lola M., Musty-Crusty Animals.)
Crab Wars: A Tale of Horseshoe Crabs, Bioterrorism, and Human Health

Biology and Conservation of Horseshoe Crabs

The American Horseshoe Crab 

Thousands of Red Knots migrate through New Jersey

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