7:30 AM EDT, March 15, 2013
In his recent letter ("Cats: Natural born killers," March 9), Kurt Schwarz of the Maryland Ornithological Society asserted that cats kill billions of birds in this country each year. He encouraged people to review the scientific literature on birds and their predation. A key study was the Smithsonian Institute's study on bird deaths published in 2011. The study investigated juvenile post-fledging survival for gray catbirds in three particular locations in the suburbs of Washington, D.C. This study included 69 birds, 42 of which died. Of these deaths, nine were attributed to cat predation, and the rest were attributed to other predators or other causes.
The study focused on a specific bird species at a specific age in a specific location, and included a very small sample size. Other studies of bird predation have similar characteristics. It is methodologically incorrect to use such findings to estimate national impacts on the bird population. Such samples are not representative of the national population and the small sample size makes national projections statistically meaningless.
Using statistics to demonize a particular animal such as cats is a fruitless exercise. It would behoove the Smithsonian Institute to work with other animal groups to seek practical, humane ways to protect birds.
Ron Lambert, Timonium
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