**Acknowledgements**

This work was supported by a grant from the US Fish and Wildlife Service. The participation of EMH in this project was supported in part by the Virginia Agricultural Experiment Station under the US Department of Agriculture Hatch Program. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the US Government. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the US Fish and Wildlife Service.
