Photo by Rick Geary

One well-fed house cat in a Michigan study killed 1600 small animals (including birds) in 18 months.

Dear Matthew Alice: For two summers, mourning doves attempted to nest in our backyard. In both instances, a nest was built, eggs laid, and our family took care not to disturb the incubation process. To our great disappointment, however, neighborhood cats disturbed the parent birds to the point that the nest and eggs were abandoned. I recently read a newspaper article on the effect of loose neighborhood domestic cats on native bird populations in Wisconsin. The study found that domestic cats caused a loss of some 19 million songbirds per year in that state alone. Are these observations equally applicable to loose domestic cats here in San Diego? If so, do you think a program of public education on the problem is needed, or should the community require cats to be contained, limited in the number that may be kept, licensed, or destroyed? I find it unfortunate that those who would “save the rainforest” may be unable to see the effect of their own behavior (and that of their cats) at home, where perhaps they can be of even greater effect. — Bill Trausch, University City

From what I’ve seen around the old homestead, mourning doves are incredibly casual nest-builders and among the densest of our feathered friends. They’re cousins of the common city pigeon. They don’t do much to conceal their flat, flimsy nests, which might make them easier targets for all predators, including other birds. The ubiquitous mourning dove is officially classified as a game bird, and some 30 million a year are killed by hunters. Human-type. But there’s no doubt your broader point about house cat predation is well taken.

The average doting owner shoos cuddly, harmless Snookums out the door, waddling and burping from that feast of sirloin tips in gravy. Most likely, Snookums immediately looks for something to stalk. Even the mildest lap-cat’s brain is “wired to hunt, even when its belly’s full,” as one ecologist put it. It has nothing to do with hunger. It has everything to do with instinct. One well-fed house cat in a Michigan study killed 1600 small animals (including birds) in 18 months. The strength of the instinct varies from individual to individual. But it’s there in all of them.

Consider this depressing data from the experts (Worldwatch, Nature Conservancy, Audubon, universities, fish and game departments): Of 9000-plus bird species, 6000 are in decline, 1000 heading for extinction. Urban Wisconsin has 1295 free-roaming cats per square mile. Cats kill 1 to 3 million birds each day in the U.S. Every free-roaming cat kills 50 to 100 birds annually, and urban cats kill more than rural cats. Birds make up 20 percent of all the small animals killed by cats; the remaining 80 percent includes rabbits (47 million a year), small rodents, and lizards, which are staples in the diets of hawks, falcons, owls, and other predatory birds.

The general findings in most studies of house cat predation are consistent enough that there’s no reason to assume San Diego would be any different from Wisconsin, except in the greater number of cats allowed to roam free in our milder climate. Habitat modification and destruction are larger dangers to the world’s beleaguered songbirds, but cats are a threat, though theoretically more controllable.

Cornell University’s Project FeederWatch provides a few additional clues. FeederWatch is an annual study of bird activity at back yard feeders around the country. Cats, they say, are opportunistic predators, stalking whatever they come across first, be it bird or mammal. In urban areas, with large sparrow and other ground-feeder populations and low numbers of field mice and lizards, this might make birds more frequent cat prey. (Hawks, on the other hand, seem attracted by flocks of birds and noisy bird activity. There’s some indication, though, that feeder sites may stimulate a cat’s hunting instincts.) Feeding sites with elevated feeder platforms and ground-feeding sites far away from shrubbery gave added safety from cats.

You may not be happy to hear there are organizations around the U.S. that are dedicated to feeding and neutering some of the country’s estimated 60 million abandoned cats. There is at least one such group in San Diego. Neutering may reduce feral populations, but that’s the only benefit of the programs to the area’s birds and small wildlife.

One ecologist told me, basically, there’s little difference between a feral cat and one that has a home and an owner but is allowed to roam at will. Longevity statistics support that idea. A cat confined to a house can expect to live as long as 15 or 17 years. Free-roaming and feral cats average 3 or 4 years. They’re particularly vulnerable to parasites and illnesses acquired from their prey, including birds.

Why can’t something be done about cat control? Everyone agrees — the logistics are hair-raising, and the issue’s way too emotional for any legislator (read “politician”) to deal with. Cities have tried. Few have accomplished much. Cats have lobbyists. Cats are now the U.S.’s most popular house pet (though as many as 6 million are euthanized each year). Cat food outsells baby food. Can an appeal be made to individual owners’ consciences to be responsible and confine their cuddly killers? It’s apparently an uphill battle, even when they know it will afford Snookums a longer and much more comfortable life.