Cell towers – and, yes, cats – are responsible for substantially more bird fatalities in North America than are wind turbines, according to a new study.

WEST Inc. and two scientists from the U.S. Geological Survey and Federal Communications Commission authored the report, which was sponsored by the nonprofit American Wind Wildlife Institute (AWWI).

The study details the impact of bird fatalities at North American wind farms, and the report authors claim it is the first to measure the relative impact of those fatalities on populations of small passerines, including songbirds.

The study says all bird fatalities from North American wind turbines range from 214,000 to 368,000 annually – a small fraction compared with the estimated 6.8 million fatalities from collisions with cell and radio towers, as well as the 1.4 billion to 3.7 billion fatalities from cats. Furthermore, the study finds that, of the more than 5 billion small passerines in North America, an estimated 134,000-230,000 – or less than 0.01% – collide annually with wind turbines.

"While total fatality numbers inform the scale of the issue, one of the most important scientific contributions from this research is our new understanding of the level of impact on individual songbird and other small passerine species," says West Inc.'s Wallace Erickson, lead author of the report.

Commenting on the study's release, Terry Root, a senior fellow at the Stanford Woods Institute for the Environment, says, "These findings come just a week after new reports on some of the truly major threats that all bird populations face today, including climate change, and provide a solid and useful perspective on the relatively minor impact that wind turbines have on populations of birds."

On Sept. 8, a report by the National Audubon Society for the U.S. Fish and Wildlife Service found that climate change threatens the survival of more than half of all species of birds in North America. On Sept. 9, State of the Birds 2014, a report prepared by a 23-member partnership of government agencies and bird conservation organizations, documented the decline of many bird species in North America, particularly from loss of habitat in the arid lands and grasslands of the U.S. due to conversion of wild lands to agriculture and suburban development, among other causes.

"With comprehensive measures to further minimize impacts on birds, wind power is a growing solution to some of the more serious threats that birds face, since wind energy emits no greenhouse gases that accelerate climate change and backs more and more of those and other pollutants out of our energy mix," says Root.

The AWWI-sponsored study is published in PLOS ONE and available here.