1. Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, 100 Cheatham Hall, Blacksburg, Virginia 24061, Institute for Integrative Bird Behavior Studies, Department of Biology, College of William & Mary, Williamsburg, Virginia 23187, and Department of Biology, Virginia Polytechnic Institute and State University, 100 Cheatham Hall, Blacksburg, Virginia 24061