Morphological changes in American kestrels (Falco sparverius) at continental migration sites

Authors

Teresa E. Ely, University of Nebraska-Lincoln & Golden Gate Raptor ObservatoryFollow
Christopher W. Briggs, Golden Gate Raptor Observatory
Shawn E. Hawks, HawkWatch International & Iowa Raptor Project
Gregory S. Kaltenecker, Boise State University
David L. Evans, Hawk Ridge Bird Observatory
Frank J. Nicoletti, Hawk Ridge Bird Observatory
Jean-François Therrien, Hawk Mountain Sanctuary
Olin Allen, Cape May Raptor Banding Project Inc.
John DeLong, Eagle Environmental, Inc. & University of Nebraska - LincolnFollow

Citation

Global Ecology and Conservation 15 (2018) e00400 1-8

Comments

2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Abstract

Many American kestrel (Falco sparverius) populations are declining across North America. Potential causes include mortality from reduction in food availability, a changing climate, habitat degradation, an increase in avian predators, disease, and toxins. We analyzed American kestrel count and banding data from seven raptor migration sites throughout North America with at least 20 years of migration data. We used count data to determine the year at which the kestrel population began a significant decline and then used banding records to determine whether body mass and wing chord declined after this point. We found reductions in kestrel body mass at three sites and reductions in kestrel wing chord at five sites. Our results indicate declines in body size at the majority of sites are consistent with the hypotheses that food availability, impacts of a changing climate, or predation risk may be contributing to population declines.