1. Department of Biological Sciences, Mount Holyoke College, South Hadley, Massachusetts, USA
2. Graduate program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, Massachusetts, USA
3. Livingston Ripley Waterfowl Conservancy, Litchfield, Connecticut, USA
4. Department of Statistics, Yale University, New Haven, Connecticut, USA
5. Department of Ecology and Evolutionary Biology and Peabody Museum of Natural History, Yale University, New Haven, Connecticut, USA