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365-988 million birds killed annually in U.S. window collisions

365-988 million birds are killed in the U.S. each year in collisions with buildings, estimates a review published last month in the journal The Condor: Ornithological Applications.

The research, based on some 92,869 records across 23 studies, finds that low-rise buildings (56 percent) and residences (44 percent) rather than skyscrapers (1 percent) are responsible for most of the toll.

The results suggest that building collisions are the second largest cause of death from anthropogenic sources in the United States after domesticated and feral cats, which kill 1.4 to 3.7 billion birds per year according to a study published last year.

The study also identified species that are most prone to building collisions — the White-throated Sparrow, Dark-eyed Junco, Ovenbird, and Song Sparrow — as well as birds that are most vulnerable relative to their population size: Ruby-throated Hummingbird, Brown Creeper, Ovenbird, Yellow-bellied Sapsucker, Gray Catbird, and Black-and-white Warbler.

“Our analysis indicates that building collisions are among the top anthropogenic threats to birds and, furthermore, that the several bird species that are disproportionately vulnerable to building collisions may be experiencing significant population impacts from this anthropogenic threat,” the authors — Scott R. Loss, Sara S. Loss, and Peter P. Marra of the Smithsonian Conservation Biology Institute and Tom Will of the U.S. Fish and Wildlife Service — write.

The analysis could help efforts to reduce collisions, according to Christine Sheppard, who runs the American Bird Conservancy’s collisions campaign.

“This study presents a significantly more robust estimate and a much-needed refinement of the data on building collision mortality,” she said. “The improved understanding and credibility it provides on the issue will help us better advance collision reduction efforts such as those we’ve already seen in places such as San Francisco, Oakland, Minnesota, and Toronto.”

The American Bird Conservancy says building-owners and residents can do their part by making window glass more apparent to birds.

“Affixing a pattern of tapes or other materials to windows can help make the glass visible to birds,” the group said. “Most birds will avoid windows with vertical stripes spaced four inches apart, or horizontal stripes spaced two inches apart.”

CITATION: Loss at al. Bird–building Collisions in the United States: Estimates of Annual Mortality and Species Vulnerability. The Condor: Ornithological Applications. January 2014.

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