1. Illinois Natural History Survey, Forbes Biological Station - Bellrose Waterfowl Research Center, Univ. of Illinois at Urbana-Champaign; Havana IL 62644 USA
2. US Geological Survey, Dept of Natural Resource Management, South Dakota Cooperative Fish and Wildlife Research Unit, South Dakota State Univ.; Brookings SD USA
3. Illinois Dept of Natural Resources; Springfield IL USA
4. Dept of Biological Sciences; Univ. of Illinois at Chicago; Chicago IL USA