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Dr. Hager's bird-window research published

January  16, 2013

Dr. Stephen Hager

Dr. Stephen B. Hager, professor of biology at Augustana, has published research about the factors that cause birds to be killed by flying into windows.

“Window Area and Development Drive Spatial Variation in Bird-Window Collisions in an Urban Landscape” was published by PLOS ONE, an international, online scientific journal.

Dr. Hager, along with a small team of researchers and undergraduate students from Augustana, studied patterns of bird-window collisions (BWCs) from 20 buildings in a mix of habitats in Moline and Rock Island, Ill.

“We found that the number of collision mortalities was highly variable across the landscape, and the driving factors that influenced BWCs were the amount of windows in a building and proportion of development in which a building was found,” Dr. Hager said.

“For example, BWCs were highest at buildings, such as offices, with lots of windows — about 50 fatalities in a year — and no fatalities were found at small houses. Also, BWCs were highest at buildings in green space and non-existent in highly developed areas.”

Previously published reports suggested that BWCs occur wherever birds and windows co-exist, and that more birds die from window collisions than any other human-related threat. The most widely cited estimate asserts that 1-10 fatalities occur each year at every building in the United States, which estimates more than 1 billion birds die annually.

Dr. Hager said the new research points out that BWCs may not be as widespread and common as is currently believed — that only a small number of vulnerable species are affected in high-risk areas, and the results call into question the utility of broad-scale estimates of BWCs, e.g., 1-10 collision fatalities per building per year.

“Applying an overall mortality estimate for one large city or the entire United States distracts us from understanding the complex nature of this issue, that is the driving factors that create patches of hot spot areas for collisions,” said Dr. Hager.

“Despite these findings, we are obligated to reduce the impacts of windows on wild bird populations, and knowing of the driving factors of BWCs allows one to predict the magnitude of mortality for each building across the landscape. This is beneficial to bird conservationists because it allows them to focus conservation efforts in hot-spot areas and ignore buildings that that pose little risk of BWCs.”

Dr. Hager believes urban planners could minimize future collision mortality by constructing buildings in areas away from green space, and architects could design buildings with windows and BWCs in mind.

Working with Dr. Hager on the research team was Dr. Bradley Cosentino, a 2004 Augustana graduate who now is a biology professor at Hobart and William Smith Colleges, Geneva, N.Y. Dr. Cosentino helped design the study and analyze the data.

Augustana students, including Kirsten Bjornson ’11, now in graduate school for neuropharmacology, worked as field technicians who surveyed the study buildings for carcasses resulting from window collisions.

Other contributors include Kelly J. McKay, Cathleen Monson, Walt Auurdeeg and Brian Blevins, local bird enthusiasts and experts who collaborated with Dr. Hager to design the experiment and complete the field work.

Published by PLOS, a nonprofit organization, PLOS ONE is a peer-reviewed journal that publishes reports on primary research from any scientific discipline. PLOS ONE is freely accessible online, offering fast publication times and community-based dialogue on articles.

Sam Schlouch
Senior Communication Director
(309) 794-7833