A feline creeps through the undergrowth, its yellow eyes fixed on the animal it is tracking, then pounces, leaping and ensnaring its prey with its claws. As the cat’s mouth closes on the unfortunate creature, it squeals and writhes, trying to escape, to no avail . . .

But this is no scene out of a nature documentary about a tiger or leopard. This is my backyard and the feline in question is a female cat that has been roaming the neighborhood and my yard for the past few months. When she first appeared, I thought for a moment that she was our resident groundhog, because she was seated just outside our veggie garden, as the groundhog was wont to do. Then I saw the black and tan strips. I tried to chase her, but she just flopped over and exposed her stomach, as if she wanted me to pet her. Then I went inside and grabbed a rolled-up camping mat to chase her with. I had no intention of hitting the cat, just scaring her, and it worked. She ran, and I chased her to the gate that leads out to the field behind our house. My feeling of relief was short lived, and I soon felt a twinge of guilt and worry, thinking, What if she can’t get back home or gets attacked by something out in the field, an off-leash dog or a fox?

I needn’t have worried. A few days later, there she was again, sunning and licking herself near the garden as if she owned the place. She did the same stomach roll, and thinking she likely wouldn’t scratch me, I picked her up and deposited her outside another gate, this one leading to the front of our property and out to the street. Then, figuring she was getting in from under our gates, I took some large pieces of firewood from our stash and placed them at the bottom of all three. That didn’t deter her at all. My husband, David, was first to witness her jumping up to the top of one of the gates and then jumping down into our yard. Now what?

Don’t get me wrong. I’m not a cat hater. Far from it. But I am a strong believer that cats should be kept indoors. In the U.S., outdoor cats are responsible for the deaths of between 1.4 and 3.7 billion birds, and between 6.9 and 20.7 billion small mammals, such as meadow voles and chipmunks. While I love all animals, if you asked me to choose between an outdoor cat and a bird, the bird would win out every time. While I can’t really claim to be a birder (no “life list,” and I can’t distinguish among all the sorts of sparrows that visit my yard—though, of course, I can identify the invasive house sparrow, the kudzu of the bird world), my love of birds has me feeding our backyard birdies and giving them water.

Back to the cat, whose name, according to a tag on her collar, is Luna. She gradually won us over, coming up to us while we sat on our back porch or in our gazebo, jumping up on our lap, or lying across newspapers we were reading, purring, stretching out, offering her tummy for a rub. I began to feel conflicted: Luna was turning out to be a very sweet cat, but she was still an outdoor cat. Despite myself, I started to look forward to seeing her in my yard, and when I was out there with her, I kept a careful eye to make sure she didn’t get anywhere near our bird feeder or bath.

Then came the day David and I were engaged in a major fall cleanup of our veggie garden. Luna turned up and after coming to us for some petting, settled near the garden, licked herself, then rolled up for a nap. She was still sleeping when we finished our work and went into the house. A little while later, I went back outside to collect some late-season raspberries from our bushes at the back. As I approached the bushes, I heard squealing, looked down, and caught sight of Luna with a vole in her mouth. The cat was under a shrub, but I managed to catch hold of her and tried to make her drop the vole. Luna held on to her prey and got away, but I grabbed her a second time and shook her, and she dropped the vole, which quickly scampered away. Luna then immediately started searching intently for the vole, and I could do nothing to deter her. I certainly tried, grabbing and depositing her outside the gate, but she immediately jumped up to its top and back into our yard and continued searching. I stayed out there for a while longer, following Luna around as she stalked beneath the shrubs and flowerbeds. I don’t know what became of the vole, as I eventually gave up and went back into the house.

Now when Luna comes, I ignore her or pick her up and place her outside the gate, hoping she’ll take her hunting elsewhere. But whenever I put out seeds or put water in the birdbath, I feel like I’m setting the table for Luna and luring birds to their deaths. I’ve witnessed her jumping up onto the baffle below the birdfeeder (maybe just trying it out; there were no birds around right then). I’ve also found some feathers around the feeder from time to time, and hope against hope that if a bird has died, that it died being a meal for a hawk and not being the plaything of a cat. For that’s what people who allow cats outdoors to stalk and catch birds or voles or chipmunks don’t understand: Their pets don’t kill because they’re hungry. They kill because it’s their instinct. And since domestic cats aren’t native to North America, maybe they should be considered an invasive species themselves—especially the outdoor variety.

I called the number I found on Luna’s tag and left a message asking that she be confined to her yard (there are ways!) or kept indoors, but so far, I haven’t heard back. If you own cats, please, please, please keep them indoors! Billions of birds and small mammals will thank you, and so will I.