An Estimate of Avian Mortality at Communication Towers in the United States and Canada

Authors

Travis Longcore, The Urban Wildlands GroupFollow
Catherine Rich, The Urban Wildlands GroupFollow
Pierre Mineau, National Wildlife Research CentreFollow
Beau MacDonald, The Urban Wildlands GroupFollow
Daniel G. Bert, Carleton UniversityFollow
Lauren M. Sullivan, University of California, Los Angeles
Erin Mutrie, National Wildlife Research CentreFollow
Sidney A. Gauthreaux Jr., Clemson UniversityFollow
Robert L. Crawford, United States Department of Agriculture/Wildlife ServicesFollow
Michael L. Avery, USDA/APHIS/WS National Wildlife Research CenterFollow
Albert M. Manville II, U.S. Fish and Wildlife ServiceFollow
Emilie R. Travis, University of WisconsinFollow
David Drake, University of WisconsinFollow

Date of this Version

4-2012

Citation

PLoS One 7(4) April 2012 e34025

Abstract

Avian mortality at communication towers in the continental United States and Canada is an issue of pressing conservation concern. Previous estimates of this mortality have been based on limited data and have not included Canada. We compiled a database of communication towers in the continental United States and Canada and estimated avian mortality by tower with a regression relating avian mortality to tower height. This equation was derived from 38 tower studies for which mortality data were available and corrected for sampling effort, search efficiency, and scavenging where appropriate. Although most studies document mortality at guyed towers with steady-burning lights, we accounted for lower mortality at towers without guy wires or steady-burning lights by adjusting estimates based on published studies. The resulting estimate of mortality at towers is 6.8 million birds per year in the United States and Canada. Bootstrapped subsampling indicated that the regression was robust to the choice of studies included and a comparison of multiple regression models showed that incorporating sampling, scavenging, and search efficiency adjustments improved model fit. Estimating total avian mortality is only a first step in developing an assessment of the biological significance of mortality at communication towers for individual species or groups of species. Nevertheless, our estimate can be used to evaluate this source of mortality, develop subsequent per-species mortality estimates, and motivate policy action.