http://catnet.stanford.edu/articles/understd_pred.html
Understanding Cats and Predation
From Alley Cat Allies website © 2000. Reprinted with permission.
While many studies have shown that cats do not have a detrimental impact on wildlife on continents, there are several who feel that cats are to blame for the depletion of songbirds and other animals. Two studies most often quoted are the Stanley Temple study and the Churcher /Lawton study. Some groups use these studies in misguided effort s to discredit our work to humanely control feral cats. Over sixty studies have been done on different continents all showing three very important points:
• Cats are opportunistic feeders, eating what is most easily available. Feral cats are scavengers, and many rely on garbage and hand-outs from people.
• Cats are rodent specialists. Birds make up a only small percentage of their diet when they rely solely on hunting for food.
• Cats may prey on a population without destroying it. If this weren't so, we would no longer have any mice around.
Even though some cats can become efficient hunters and do kill birds, many international biologists agree that only on small islands do cats possibly pose a severe threat to the wildlife populations. They agree with biologist C.J. Mead that "Any bird populations on the continents that could not withstand these levels of predation from cats and other predators would have disappeared long ago..."
And finally, while many concentrate their efforts on blaming cats, the real culprit homo sapiens, goes free; continuing the destruction of habitat, hunting and killing, and using pesticides that endanger entire populations of wildlife, including millions of birds. The following is a collection of opinions from experts who have studied predation and who do not lay the blame on cats.
The above is an excerpt from the link I posted.
There is nothing that is going to deplete a animal population like a lack of food/breeding spaces, so in other words their natural habitat. If you look at what is happening with our exploding human population of clear cutting for subdivisions where homes are put on lots that have no space for trees. In our cities, the rich are buying up residential lots, and expanding the current house so it is brimming to the edge of property lines. Manicured lawns and gardens that aren't growing plants that provide natural food for the birds (let that thistle grow, the finch love the seeds).
Some facts based on the Churcher and Lawton study:
"Studying the hunting trophies brought home by 78 cats in a single English village, Peter Churcher and John Lawton found birds were 35 percent of the kill-by far the highest estimate in any such study. In a 1989 condensation for Natural History magazine, they multiplied their results by the estimated number of cats in the entire nation. Rarely are projections made with such limited data, except in junior high science projects - which may be an appropriate comparison, considering Churcher teaches at a boys' school.
And on the Wisconsin statement:
'Researchers in Wisconsin cite cats for killing 19 million songbirds.'
"Doctor Stanley Temple, co-author of this frequently quoted work, seemed exasperated when asked again to rehash his findings. 'The media has had a field day with this since we started," he sighed. Those figures were from our proposal. They aren't actual data; that was just our projection to show how bad it might be.' No one interviewed has seen Temple's unpublished research.
"But the [Sonoma County] supervisors appeared to give special attention to a letter written by Drs. Peter Connors and Victor Chow, UC/Davis researchers working at the Bodega Marine Laboratory. By projecting the numbers cited from Wisconsin and Great Britain, they estimated 500,000 Sonoma County birds are killed by cats annually. In a telephone interview, Connors said he has read only the condensation of the British study and has seen only "extracted forms" of Temple's work-which, of course, were guesstimates for the proposal. He was surprised to learn this study was unpublished. 'Look, we're not cat researchers,' said Connors. 'I've never worked with cats at all; I'm an ornithologist.' Then what expertise does he have about cats? 'Vic (Chow) has been participating in a mentor program with Piner High School students on a project tracking feral cats,' he explained. 'We had (radio transmitter) collars on three animals. We didn't do a full study; it's just a program with high school students.'"
As Hazel stated, people are going to do what they want to do.