Catch-and-release may be great for fishing, but many wildlife biologists, veterinarians and environmentalists feel catching and releasing feral cats is a terrible idea. Local wildlife certainly finds the practice terrifying — and deadly.

Cats, not native to America, add an unnatural, lethal dimension of tooth and claw to the outdoors. The problem is convincing far-divorced-from-nature cat lovers that free-roaming cats are serious killers taking a staggering toll.

An estimated 80 million feral cats prowl the outdoors. Studies show that Wisconsin alone annually loses 17 million to 30 million songbirds to them. Minimally, feral and domestic cats annually kill 100 million to 300 million songbirds in America. Some estimates put the number closer to 1 billion.

As a bird-banding researcher working to contribute to their survival, I find those numbers appalling. With migratory songbird populations diminishing from habitat destruction both here and in the tropics, where they winter, this trend can’t continue without devastating results.

The slaughter is especially brutal now. In late May and early June, the first, still-flightless fledglings begin leaving their nests. Grounded for several days afterward, they beg to be fed by their frenetically foraging parents. Their cries are easily detected by cats instinctively programmed to hone in on those sounds. It’s like picking cherries for them, with studies revealing that some particularly proficient cats are capable of taking more than 20 fledglings in a day, despite parent birds’ attempts to distract and dissuade the hunters.

In my backyard — and many of yours, I’m sure — the heavy toll is being taken again. My family has observed two neighbors’ cats — one is orange and white, the other black and white — no doubt quite adorable at home, killing birds already this year.

Our neighbors who open their doors to let their cats prowl freely are oblivious to the carnage they’re responsible for. There’s little we can do to stop them. Wildlife lovers who are desperately tempted to kill a feral cat to save hundreds of wild animal lives risk severe penalties. Only the people who let cats out have the power to stop the killing.

Several states, including Massachusetts, have humane organizations (obviously not with wildlife priorities) that are trapping, neutering and releasing feral cats, often after efforts to make them healthier wind up unintentionally making them better killers. Neutering is a responsible first step, but if there is no plan to subsequently find feral cats an indoor home, they shouldn’t be returned to the wild to survive by randomly killing wildlife. At best, the practice appeases people who oppose euthanasia, but in total adds greatly to animal suffering.

The wandering cat is a vestige of our European roots and agricultural past when cats born in homes and barns had positive functions — controlling disease-ridden, crop-destroying rodents in an environment that was primarily farmland and agricultural fields. Those days are gone, and the birds that millions of outdoor cats are killing can’t continue to withstand the losses.

World bird authority Peter Alden wrote me recently underscoring the devastation. A suburban Baltimore study of 100-plus catbird nests showed that within days of leaving their nests, 70 percent of the fledglings were killed by cats.

A national educational effort would be needed to significantly change long-ingrained habits of pet owners who assume their right of ownership to let their cats roam free. They need to know they are killing with their permissive kindness.

Veterinarians know that housecats are far healthier when kept at home where they belong, and where they can’t devastate wildlife. As our most respected weapon for animal health, all veterinarians should have an awareness of wildlife welfare and help convince the public of this national problem — not contribute to it.

Concord recently tried to pass a cat law that would have restricted cats to their own yards or otherwise be under control. The effort failed. People with little wildlife experience or knowledge about birds have difficulty envisioning the vast scope of cat killings. How do we change a cultural tradition? It would take another Rachel Carson’s “Silent Spring” to awaken us.

But we can be locally effective and individually responsible, like Shrewsbury’s Joe Kavacian. Recognizing his own cat’s brutal impact on wildlife, Kavacian began keeping his cat inside. That’s not as easy as just opening the door and expediently letting one’s problem disappear. Kavacian has undoubtedly saved many songbirds through his efforts.

We can’t blame cats for killing. That’s what they’re genetically programmed to do. I personally love cats, having spent much of my life studying and filming magnificent wild ones making kills in Africa.

It’s people who are to blame here for adding an unnatural predator to our wild lands. If we own housecats, we should keep them in our houses. If we have an opportunity to remove them from the killing fields, we should ethically do so.