View From Sapsucker Woods: The Inescapable Toll of Outdoor Cats on Birds

Early in my life a stray cat that was roaming our family’s backyard became a cherished household pet, still spending lots of time outdoors but also basking indoors amid lots of love and food. My brothers and I got a great lesson in where babies come from when Patches bore kittens in my bedroom closet. Then the real show began. Nearly every morning we found sparrows, goldfinches, buntings, mice, shrews, moles, and even flying squirrels, sometimes delivered all the way to my closet. We kept a male from that first litter, and later adopted another stray. Even in college, my roommate and I illegally kept a cat in our dorm room.

I offer these pet-owner confessions because my outspoken convictions about the ecological impacts of domestic cats often get written off as the rants of a “cat hater,” which I am not. I love and admire cats as endlessly fascinating, independent personalities, playful companions, and even—on their terms—affectionate and loving members of the households they control.

Among the instinctive cat behaviors that fascinate us are stalking, pouncing, chasing, catching, and playing with objects. All domestic and feral cats practice these behaviors as kittens, and express them as adults throughout their lives, exactly as wild felines have throughout the 25-million-year evolution of this remarkable carnivore lineage. This tight link between domestic and wild cats carries one crucial step further, of course. Outdoors, the hunting behaviors described above culminate in a kill.

Many cat owners deny that their sweet tabby regularly kills birds and mammals while roaming outdoors, but these are wishful thoughts. Critter-cam videos reveal that even the most docile and adorable of our household kitties routinely dispatch small vertebrates when outdoors, and this brings us to the heart of the matter. Today, landscapes all over the world are crawling with domestic cats (household or feral), each one trying to kill something virtually every day.

A recent, landmark analysis estimated that every year in the United States alone, free-ranging domestic cats kill between 1.4 and 3.7 billion birds, and from 6.9 to 20.7 billion small mammals. (S. R. Loss, T. Will, and P. P. Marra. 2013. The impact of free-ranging domestic cats on wildlife of the United States. Nature Communications 4: 1396/ncomms 2380)

The authors conclude that predation by domestic cats likely constitutes the “single greatest source of anthropogenic mortality for U. S. birds and mammals.” Their study elevates to a new level the scale of the problem and the urgency of achieving solutions. Domestic cats roaming our yards, neighborhoods, pastures, and local parks constitute an enormous population of subsidized recreational killers.

Hats off to the many responsible cat owners who already keep their cats indoors. May your legions grow as this new study gets publicized. Even more important, we need concerted public efforts to reduce the abundance of unowned cats, because these execute the lion’s share of the killings. Continentwide, thousands of feral cats roam through wild spaces that otherwise could support healthy bird populations and balanced ecological communities. It is outrageous that feral cat colonies are encouraged in many communities, and even permitted by some public agencies. “Trap-neuter-release” (TNR) programs are utterly ineffective at controlling cat populations or cat predation, notwithstanding their advocacy by the many “animal rights” groups that openly ignore the rights of native animal populations.

It is time for a sweeping change in our tolerance of freeranging domestic cats. If you own a cat, please heed and spread the word: keep your cat indoors. More important, all of us must work to convince the managers of municipalities and public open spaces to curtail the practice of allowing feral cats to persist on our lands. Citizens across the country can amplify the call for banning this ecologically intolerable practice. Nobody should blame the cats for this unsustainable killing, because it is their nature. Rather, this is a pervasive human mistake, and even we cat lovers must grasp the enormity of the problem it has caused.