1. National Institute of Standards and Technology, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, South Carolina 29412, USA
2. Current address: Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, Florida 34211, USA
3. Department of Zoology, Michigan State University, 203 Natural Science Building, East Lansing, Michigan 48824, USA
4. The Avian Conservation Center and Center for Birds of Prey, PO Box 1247, Charleston, South Carolina 29402, USA