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Outdoor cats: single greatest source of human-caused mortality for birds

Posted on 8. April, 2013.

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A new study by scientists from the Smithsonian Conservation Biology Institute and the US Fish and Wildlife Service has found that bird and mammal mortality caused by outdoor cats in the United States is much higher than has been widely reported. The study which was based on a review of 90 previous studies, was published in the online research journal Nature Communications.

The study was authored by Dr Peter Marra and Scott Loss, research scientists at the Smithsonian Conservation Biology Institute and by Tom Will from the US Fish and Wildlife Service’s Division of Migratory Birds.

According to Dr George Fenwick, President of American Bird Conservancy, "This study demonstrates that the issue of cat predation on birds and mammals is an even bigger environmental and ecological threat than we thought. No estimates of any other anthropogenic mortality source approach the bird mortality this study calculated for cat predation.”

The study estimated that the median number of birds killed by cats annually is 2.4 billion. This may exceed all other direct sources of anthropogenic bird mortality combined such as collisions with windows, buildings, communication towers, vehicles, and pesticide poisoning.  About 69% of the bird mortality from cat was from un-owned cats, which includes farm/barn cats, strays that are fed but not granted access to human habitations, cats in subsidised colonies, and cats that are completely feral.

The paper “The impact of free-ranging domestic cats on wildlife of the United States” by Scott R. Loss, Tom Will and Peter P. Marra was published in Nature Communications 4, 1396, doi:10.1038/ncomms2380.

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