1. Smithsonian Tropical Research Institute , WF89+C43, Amador Causeway, Panamá , Panama
2. Department of Integrative Biology, University of Texas , Austin, TX 78712 , USA
3. Lab of Ornithology, Cornell University , Ithaca, NY 14850 , USA
4. Department of Biology, University of Washington , Seattle, WA 98195 , USA