Wild Georgia: Migrating shorebirds feast on horseshoe crab eggs

Shorebirds known as red knots gorge on high-energy horseshoe crab eggs enroute to Arctic nesting grounds. An egg-laying horseshoe crab is in the foreground. 
(Courtesy of U.S. Fish and Wildlife Service)

Credit: Handout

Credit: Handout

Shorebirds known as red knots gorge on high-energy horseshoe crab eggs enroute to Arctic nesting grounds. An egg-laying horseshoe crab is in the foreground. (Courtesy of U.S. Fish and Wildlife Service)

A frenzied feast is taking place now on Georgia’s coast as tens of thousands of migrating shorebirds stop to refuel enroute to summer nesting grounds in the Arctic.

Most ot the birds -- dunlins, willets, sanderlings, sandpipers, red knots, ruddy turnstones, plovers, whimbrels -- face a dire timetable. They departed in February from winter grounds in Central and South America to head to the Arctic. There, they will have only a few weeks of favorable weather to mate, build nests and lay eggs. By July, they will start heading back south.

With its abundant food resources, Georgia’s coast is a vital stopover for the birds, whose intense feeding quickly restores body fat that provides energy for the rest of their trek north. On coastal salt marshes, mudflats and barrier beaches, the shorebirds gorge on countless horseshoe crab eggs, fiddler crabs, clams, crustaceans and other energy-rich food.

Of these foods, the most important by far are the billions of eggs laid by horseshoe crabs. Coinciding with the shorebirds’ migration, hundreds of thousands of prehistoric-looking horseshoe crabs are spawning and laying eggs now along Georgia’s coast and other coastal areas as far as New Jersey.

Many shorebirds feed almost exclusively on the eggs during their re-fueling stopovers. Horseshoe crab numbers, however, are plummeting, due largely to over-harvesting by people. The crabs are harvested by the hundreds of thousands for their blood, which is used by pharmaceutical and medical industries to test products for bacterial contamination. No other test for that purpose is as reliable. Untold numbers of horseshoe crabs also are caught annually for use as bait fish.

That all spells trouble for shorebirds as well as humans.

Georgia and other coastal states have put strict limits on horseshoe crab harvesting, and the pharmaceutical industry is trying to perfect a synthetic test to spare the need for horseshoe crab blood. The hope is that the measures will help save the crabs and the shorebirds as well.

IN THE SKY: From David Dundee, Tellus Science Museum astronomer: The moon will be first quarter Thursday night. Venus is in the west at dusk and will appear near the moon Monday night. Mars is in the southwest at dark and will appear near the moon Wednesday night. Jupiter and Saturn are low in the east just before dawn.

Charles Seabrook can be reached at charles.seabrook@yahoo.com.

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