Birds & Cats: Keep Cats Indoors
There are 60 to 90 million pet cats in the United States today , and it is estimated that 25 to 66% of cat owners allow their cats outdoors . Add to that the tens of millions of strays and feral cats and there is certainly a sizable population of free-ranging cats in our country. Studies  have indicated that 60 to 70% of a cat’s prey is small mammals, 20 to 30% birds, and 10% other animals including reptiles, amphibians, and insects.
Free-roaming cats clearly have an impact on wildlife! If each outdoor cat only killed one bird per year, it would equal over 60 million birds annually. Here are some references:
- The University of Wisconsin’s Dr. Stanley Temple estimates that rural cats kill 39 million birds every year in Wisconsin alone.
- Another well-reasoned calculation, by one of Audubon’s senior scientists, puts the estimate at over a billion birds per year.
- This January 2003 paper to the U.S. Fish and Wildlife Service offers detailed discussion on the impact of free-roaming cats in Florida (pdf).
- The abstract of a 2003 paper  by Michigan State University researchers in the scientific journal Biological Conservation (used with permission):
Fluctuations of bird abundances have been attributed to such factors as supplemental feeding, landscape change, and habitat fragmentation. Notably absent from consideration, however, is the role of private landowners and their actions, such as owning free-ranging domestic cats (Felis catus; cats allowed free access to the outdoors). To understand the impacts of cat predation on birds, we surveyed all 1694 private landowners living on three breeding bird survey (BBS) routes (~120 km) that represent a continuum of rural-to-urban landscapes in Southeastern Michigan, where the majority (>90%) of land is privately owned. Our data indicate that among the 58.5% of landowners that responded, one quarter of them owned outdoor cats. On average a cat depredated between 0.7 and 1.4 birds per week. A total of 23+ species (12.5% of breeding species) were on the list of being killed, including two species of conservation concern (Eastern Bluebirds and Ruby-throated Hummingbirds). Across the three landscapes there were ~800 to ~3100 cats, which kill between ~16,000 and ~47,000 birds during the breeding season, resulting in a minimum of ~1 bird killed/km/day. While the number and density (no./ha) of free-ranging cats per landowner differed across the rural to urban landscapes, depredation rates were similar. Landowner participation in bird feeding showed no relationship with the number of free-ranging cats owned. Similarly, selected demographic characteristics of landowners were not significantly related to the number of free-ranging cats owned. Our results, even taken conservatively, indicate that cat predation most likely plays an important role in fluctuations of bird populations and should receive more attention in wildlife conservation and landscape studies.
The Wildlife Society notes in its position statement on feral cats , “Extensive popular debate over absolute numbers or types of prey taken is not productive. The number of cats is undeniably large. Even if conservative estimates of prey taken are considered, the number of prey animals killed is immense.”
Sandy Beck, a journalist with the Tallahassee Democrat, asked an Internet wildlife rehabilitation chat group: “What percentage of your wildlife patients are victims of outdoor cats?” Responses from professional rehabbers around the country ranged from 14 to 30 percent.
This article from the Vermont Center for Ecostudies summarizes several more recent studies.
The American Bird Conservancy has launched a national campaign to educate cat owners and encourage them to keep their cats indoors. Not only does wildlife benefit, so do the cats: While outdoor cats commonly have a life expectancy of fewer than 5 years, indoor cats can live for up to 17 years. With less exposure to disease, other cats and animals, and fewer opportunities to have accidents (1.5 million cats are killed by autos annually), vet bills are less and cats live healthier lives!
Q and A
Some pet owners are quite resistant to keeping their cats indoors. Here are some common misconceptions, adapted from Sandy Beck’s article in the Tallahassee Democrat, a Peterson Online discussion with representatives from the ABC, an article from Bird Conservation (the ABC magazine), and the U.S. Fish and Wildlife Service.
Q: If I keep my cat well-fed, won’t that stop her from killing birds?
No. “The (cat’s) urge to hunt is independent of the urge to eat,” explains Desmond Morris, author of the book Catwatching. “Cats hunt for the sake of hunting.” And your outdoor cat is likely killing birds even if you don’t know it.
Q: So isn’t my cat’s hunting instinct natural?
A: Yes, but house cats are not natural in the environment. They have been introduced in vast numbers and at high densities. Our local wildlife have evolved specific adaptations to deal with other predators — raccoons, opossums and hawks — but not house cats.
Opening the back door to allow kitty out to do what’s natural for her disrupts the delicate balance with potentially disastrous effects on wildlife and the entire ecosystem.
A: Cat’s can be perfectly content indoors. A great exercise solution: Get two cats! Cats enjoy chasing each other around the house, which is just as entertaining for us. A sunny window sill or screened porch, preferably with a view of the bird feeders (kitty TV), will provide all the vitamin D they need (have you ever known a cat not to find a sunny spot to sit in?). You will also appreciate keeping the ticks and fleas on the other side of the screen. The book 101 Cool Games for Cool Cats was written with keeping indoor cats happy and engaged should you be short on ideas.
Q: Don’t cats help control rats and mice?
A: Cats do kill rodents, many of which are native, non-pest species that are important prey items for other wildlife. As for rats, cats don’t tend to tackle rats over 6 ounces (adult rats weigh 7-12 oz). Hey: do you really want your cat tangling with rats anyway?
What You Can Do
- Keep your cat indoors and encourage cat-owning neighbors to do the same
- Spay or neuter your cat. In this country, 35,000 kittens are born each day, and one female and her kittens can produce 420,000 cats in seven years.
- Never abandon cats outside. This is cruel and inhumane to both the cat and local wildlife. Take the cat to an animal shelter where it has a much better chance of being adopted into a loving home and living a long and healthy life.
- Support cat licensing laws, leash laws, and higher licensing fees for cats that aren’t spayed or neutered.
- Don’t feed stray cats. Subsidizing outdoor cats is not a solution, and “trap-neuter-release” policies do not work to reduce feral cat numbers. A very thorough web site on this topic is TNR Reality Check; it lists many conservation organizations, government agencies, and veterinary groups that oppose TNR.
 60 million based on 1990 U.S. Census (people responding that they own cats); over 68 million according to the American Veterinary Medical Association (AVMA) 2001 U.S. Pet Ownership & Demographics Sourcebook: 90 million based on the American Pet Products Manufacturer’s Association’s 2005/2006 National Pet Owners Survey.
 National People and Pets Survey, 1995; see also .
 Figures and citations within Impacts of feral and free-ranging domestic cats on wildlife in Florida; see also literature above.
 Lepczyk, C.A., A. G. Mertig, and J. Liu. 2003. Landowners and cat predation across rural-to-urban landscapes. Biological Conservation 155:191-201.
 Position Statement on Feral and Free-Ranging Domestic Cats, The Wildlife Society (pdf). The Wildlife Society also maintains an excellent blog and devotes an entire category to the problems with feral cats.