Marra [Pete Marra, animal ecologist with Smithsonian Conservation Biology Institute] and his colleagues are looking at human-related causes for bird and wildlife deaths in the country, from windmills and glass windows to pesticides.
But first, Marra and his team looked at the impact of the feline population, one of the biggest putative causes of bird demise in the country. [emphasis added]
While past studies had used critter cams or owner reports to estimate the number of birds killed by cats, those studies were usually small and not applicable to the entire country, Marra told LiveScience.
For this broader analysis, the team first looked at all prior studies on bird deaths and estimated that around 84 million owned-cats live in the country, many of which are allowed outdoors.
"A lot of these cats may go outside and go to 10 different houses, but they go back to their house and cuddle up on Mr. Smith's lap at night," Marra said.
Based on an analysis of past studies, the researchers estimated that each of those felines killed between four and 18 birds a year, and between eight and 21 small mammals per year.
But the major scourges for wildlife were not those free-ranging, owned-cats, but instead feral and un-owned cats that survive on the streets. Each of those kitties — and the team estimates between 30 million and 80 million of them live in the United States — kills between 23 and 46 birds a year, and between 129 and 338 small mammals, Marra said.
|The Florida Scrub Jay, only one species of bird whose numbers are dwindling.|