About the Authors

Claudia Mettke-Hofmann

C.C.Mettke-Hofmann@ljmu.ac.uk

Affiliations School of Natural Sciences & Psychology, Liverpool John Moores University, Liverpool, United Kingdom, Smithsonian Migratory Bird Center, National Zoological Park, Washington, D. C., United States of America

Hans Winkler

Affiliation Konrad-Lorenz-Institut of Ethology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna, Austria

Paul B. Hamel

Affiliation Southern Hardwood Laboratory, U. S. Forest Service, Stoneville, Mississippi, United States of America

Russell Greenberg

Affiliation Smithsonian Migratory Bird Center, National Zoological Park, Washington, D. C., United States of America

Competing Interests

Claudia Mettke-Hofmann is a PLOS ONE Editorial Board member. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials.

Author Contributions

Conceived and designed the experiments: CMH RG. Performed the experiments: CMH. Analyzed the data: CMH. Contributed reagents/materials/analysis tools: RG PBH HW. Wrote the paper: CMH HW PBH RG.