Dear Umbra,

I have three cats, and live in a close-in suburb of Boston. I love the cats dearly, and let them outside during the day to wander about, and generally not have to live an indoor, sedentary, boring life. My question concerns their hunting instincts: I haven’t had any luck with any particular way of preventing them from killing birds, mice, etc. I worry most about the birds, having read repeatedly that the millions of pet cats we have in this country really do a number on songbirds and other birds. I’ve put bells on them (more than one per cat), I feed them well and regularly, and don’t feed them anything approaching a recognizable animal. I keep them in at night, after reading that’s when they do the most damage, but I still get at least a bird a month, and often more. I read about a gizmo in Australia that does inertial sensing of when the cat leaps and makes sound and light, but it was very expensive, and I’m not even confident it’d work. Any suggestions?

Richard Soenneker
Malden, Mass.

Dearest Richard,

Grist thanks its sponsors. Become one.

I am answering your question at the request of a dear friend. She believes that if cat owners only knew the impact their cats have on songbirds, they would keep their cats indoors. We will see.

The cat that swallowed the canary.

Photo: iStockphoto

Grist thanks its sponsors. Become one.

You’ve read all the reasoning behind the indoor cat recommendation, I’m sure, so let us see if we can shock others into compliance. Here are the accepted facts about domestic cats and their decimation of the songbird population.

Cats are natural hunters, and no matter how well satiated you keep them, they still want to practice their hereditary skills. I suppose if you spooned Meow Mix into a cat until it was comatose it wouldn’t hunt, but a regular old self-regulating cat probably finds a good meal fuel for a nice prowl about the neighborhood. It is not a natural predator-prey relationship: Household cats have an unfair advantage over other bird predators (and their prey) in that their food source is constant, and their own populations will not fluctuate if their prey’s population declines.

Several oft-cited studies form the basis for an estimate of 100 million to 1 billion U.S. songbirds killed annually by domestic cats. One study, from the University of Wisconsin, finds that a reasonable estimate is 39 million birds killed by cats each year — in Wisconsin alone. Here’s a dramatic quote from the same study: “Worldwide, cats may have been involved in the extinction of more bird species than any other cause, except habitat destruction.” The University of Florida Conservation Clinic, in a report to the Fish and Wildlife Service, estimated that a free-roaming cat kills 100 mammals and birds per year.

These and other studies are the driving force behind various campaigns to keep cats indoors, so one might tend to be skeptical — perhaps they do not cite the studies finding that cats prefer to lovingly hug birds and are misunderstood. Then one remembers that one learned math in elementary school. You say you have three cats and see more than one killed bird per month. You live in a city, where bird populations are lower than in the country, so let’s assume each of your cats actually kills two birds per month. I think that sounds reasonable. Over a year, then, your pack of pets kills 72 birds. That is the low-balled price of having your cats outdoors: 72 birds per year, not including various small (perhaps endangered) mammals.

I don’t have a cat these days (and no, I did not keep my childhood best friend inside), so I have no firsthand knowledge of the bells that purportedly warn prey of death’s approach. All we can go on is the general bird powers-that-be report of failure: Cats are smart enough to learn to stalk quietly wearing the bell, or, if the bell jingles at the last moment, it is already too late. Plus the prey may not have gotten that memo about running away when it heard the bell ring. Even if the bell were effective half the time (as has been reported in one study), you’re still looking at 36 dead birds per year (to keep using you as an example). The American Bird Conservancy, which runs the Cats Indoors! Campaign, mentions two other products. One is CatAlert, a sonic cat collar from Britain, which reduced but did not eliminate bird kills, and did nothing to reduce small mammal murder. The other is the CatBib. Hee hee. It’s a neoprene bib that physically interferes with the predator’s killing stroke.

I don’t think it’s an exaggeration to say that if you value a diverse and numerous wild bird population, you should keep your cat indoors. The Cats Indoors! Campaign also highlights various benefits indoor-only life brings to cats, particularly a much longer life span. But no one thinks their own special pet kills lots of birds, or they believe living indoors causes the cat to suffer (who can say, really?), and certainly no one thinks their cat is going to be the one whose life expectancy is cut to five years instead of 17. There’s always a reason to postpone removal of culpability. We all take unnecessary small car trips that could be postponed and clumped with other errands or avoided altogether (special clause in my contract: relate everything to the automobile).

Probably the best that birds can hope for is to host bird flu in a form that is deadly to cats. Cat owners, in denial about the impact their cute pet has on cute wild animals, will come to their senses as they see increasing numbers of dead cats with birds in their mouths. Will this happen before the rising oceans cause us to stop driving? I’m on tenterhooks. By the way, before I get any angry letters — did I mention I loved my cat? And this column has been approved by a certified crazy cat lady. I’m just giving you the facts, everyone.