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Fall 1998

Research Magazine > ARCHIVE > Fall 98 > Article

Feathering Their Tests
by Steven N. Koppes

UGA researchers can tell from a single feather of a wood stork nestling where the bird lives and what it eats. How do they come to these Sherlock Holmesian conclusions? It's elemental, my dear Watson.

Geochemist Christopher Romanek of UGA's Savannah River Ecology Laboratory (SREL) can determine the telltale composition of elements he finds in a feather through stable isotope analysis.

"He can analyze a feather and tell us if that bird came from either a coastal colony or an inland colony by the carbon, because the salt marsh ecosystems utilize a different carbon than do the inland systems," said Larry Bryan, research coordinator of SREL's wood stork program.

The type of nitrogen Romanek finds indicates whether a wood stork is eating top-level wetland predators, such as large bullheads and catfish, or creatures farther down the food chain, including minnows, bluegill, crayfish and tadpoles.

"That's interesting because the higher you get up the food chain, typically, the higher mercury concentrations you're going to have in these aquatic organisms," Bryan said.

For more than 15 years now, SREL researchers have studied the endangered wood stork (Research Reporter, Winter/Spring 1996). During the past three years, Bryan has recorded mercury concentrations in wood stork nestlings. The concentrations amount to less than a millionth of a gram, but they are high enough for the U.S. Fish and Wildlife Service to consider them potentially harmful. "Some of the nestlings could be at risk," Bryan said.

The SREL studies, funded by Fish and Wildlife and the U.S. Department of Energy, have documented a regional difference in mercury uptake: Coastal nestlings have less mercury than inland nestlings. "This is due to coastal saltmarsh fish generally having less mercury than freshwater fish," Bryan said.

e-mail Larry Bryan at bryan@srel.edu.


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Wood Stork