The Effects of Free-ranging Cats on Birds in Wisconsin:
Wisconsin Bird Conservation Initiative Issues and Guidelines
S. Diehl, K. Etter Hale, W. Mueller
Note: This WBCI Issues Paper is currently undergoing a major revision
Studies in Wisconsin and elsewhere indicate that free-ranging domestic cats (Felis catus) pose a threat to birds and other wildlife.
In Wisconsin, concern about free-ranging cats was first highlighted in the mid 1990s, when a study by Coleman and Temple attempted to study predation by free-ranging cats on birds in rural locations across the state. Extrapolating the results from this study indicated that millions of birds were being killed annually in Wisconsin by cats. Because of the difficulty in studying any species living outdoors across the entire state, the exact number of birds killed annually by free-ranging cats will never be fully enumerated. However, over the past decade additional studies in the Midwest and elsewhere have suggested similar problems with cat predation on birds and should alert us to the fact that free-ranging cats are killing large numbers of birds in Wisconsin each year. Moreover, other studies have shown that cats in some habitats may be directly competing with native avian predators, such as American Kestrels (Falco sparverius), Northern Harriers (Circus cyaneus) and Red-tailed Hawks (Buteo jamaicensis) for prey. Finally, in some habitats and locales even very low cat depredation could negatively impact the breeding success and survival of a species, especially if that species is rare or endangered.
Because of concerns raised by these and other studies, a number of nationwide efforts have been developed to encourage responsible cat ownership, most notably the American Bird Conservancy’s Cats Indoors! Program. In our effort to address this concern in Wisconsin and provide assistance to both WBCI partners and the general public, we have outlined a set of recommended conservation actions and research needs pertaining to outdoor cats.
The reduction of cat predation on native birds and other wildlife will be achieved through the involvement of cat owners, WBCI endorsers, state and federal agencies, and non-governmental conservation, animal welfare, and animal sheltering organizations. At the present time we recommend the following guidelines to reduce the negative impacts of free-ranging cats on birds in Wisconsin:
- For the welfare of both cats and birds, keep your cats indoors or under your supervision and control when outdoors, and encourage others to do the same. According to the Humane Society of the United States, cats that are not allowed to roam outdoors typically live substantially longer than free-roaming cats. Indoor-only cats are much less likely to get lost, get parasites, become exposed to serious diseases, get hit by a car, attacked by a predator, or get in fights with other cats. Moreover, lost cats often go unclaimed at local pounds and animal shelters. For instance, in Milwaukee, only about 4% of cats that enter that city’s animal control shelter are reclaimed by their owners. Help in “converting” your free-ranging cat to an indoor-only cat can be found on the Wisconsin Humane Society’s website [http://www.wihumane.org/behavior/ask-the-experts/cat-behavior/training-your-cat-to-stay-inside] . Overcoming attitudinal barriers among the general public to keeping owned cats indoors or under their control when outdoors is one of the keys to long-term solutions to predation by cats on birds and other wildlife and reducing suffering for cats in our communities.
- To help reduce the numbers of abandoned/unwanted cats, spay or neuter your cats and encourage other cat owners you know to do the same. Support low-cost or free cat spay and neuter programs at your local humane society or animal shelter and support efforts to spay or neuter all cats adopted from your local animal shelter. Many animal shelters and humane societies are poorly funded and the only way such efforts can be undertaken is through public donations and support.
- Have your veterinarian “microchip” your cats to aid in their being returned to you should they become lost, and promote voluntary identification of cats in your community. A microchip is a rice-grain-sized identification device that is quickly and easily inserted under the skin of a cat’s back and can be read electronically to determine the cat’s owner.
- Support ordinances and initiatives in your community designed to humanely and effectively reduce the numbers of unwanted cats, decrease the number of homeless stray cats, increase the return of lost cats to their homes, increase the number of cats adopted into permanent homes and reduce the number of cats surrendered to shelters.
- Treat stray cats on your property humanely. Contact your neighbors to find out if the cats frequenting your property are owned. If they are, explain to the owners the impact their cats have on wildlife, the risks cats allowed outdoors face, and ask them to keep their cats indoors or under their control. If a cat’s owner cannot be found, contact your local animal control agency for advice.
- Use “habitat modification” on your property to minimize the likelihood that free-ranging cats will cause problems for wildlife: avoid feeding birds on the ground where they may be more vulnerable to predation; place your birdfeeders at least several feet away from shrubs and other cover cats may use to stalk birds; utilize non-toxic commercial repellents designed for cats or humane scare devices such as the Scarecrow (http://shop.wihumane.org/store/product/scarecrow-motion-activated-sprinkler).
- Farmers and others in the agricultural community are urged to spay or neuter the cats on their properties to control their numbers and instead of depending on cats for rodent control, control rodents by the use of pest-proofing and environmentally safe rodent control methods. Avoid the use of rodenticides (i.e. poisons), especially outdoors, since birds-of-prey (hawks and owls) can become ill or die when they eat rodents that have consumed rodenticides.
- Bird and wildlife conservation agencies and organizations, and animal welfare and sheltering agencies and organizations, should work together to achieve common goals concerning cats and wildlife.
ONGOING RESEARCH AND ADDITIONAL RESEARCH NEEDS
While the overall impact of cat predation on specific bird species at the population level in Wisconsin has not been enumerated exactly, it is clear that many free-ranging cats prey on birds. Thus, there are legitimate concerns that free-ranging cats may be a significant cause of bird mortality. With bird populations under pressure from numerous other human-initiated or -controlled threats (e.g., habitat loss and fragmentation, tower and building collisions, climate change, pollution, etc.), we need to reduce as many of these threats as possible. We have identified a number of research needs to help us better understand the effect of cat predation on birds in Wisconsin:
- In 2004, Lepczyk, Mertig and Liu studied the effects of owned, free-ranging cats on birds across urban to rural landscapes in Michigan. Ideally, similar studies should be conducted across varying landscapes and communities here in Wisconsin.
- The level of bird predation by feral cats in managed colonies across varying landscapes in Wisconsin should also be studied. Nationwide, the animal welfare community is searching for humane and effective means of controlling feral cat populations, and the establishment of managed feral cat colonies is growing in popularity. It is not well understood what threat managed feral cat colonies might pose to native bird species across urban to rural landscapes.
- Conservation biologists lack data on how specific levels of cat predation depress wildlife populations and if there are thresholds at which cat densities become a biologically significant source of mortality.
- Relatively little information exists on the human rationale of allowing cats outdoors and what factors underlie this human behavior.
- Public education efforts on this issue need to be assessed over time to investigate if people’s attitudes and behaviors change.
- What role bird window collisions play in the numbers of birds recovered by free-ranging cats.
These six points represent specific next steps for conservation research on the free-ranging domestic cat in Wisconsin, but by no means is an exhaustive list.
EDUCATIONAL INFORMATION AND RESOURCES
- American Bird Conservancy’s Cats Indoors! program: Information, fact sheets, brochures.
- Wisconsin Humane Society:
- Keep Your Cat Inside -- http://www.wihumane.org/behavior/ask-the-experts/cat-behavior/keep-your-cat-inside
- Enrichment for Your Cat -- http://www.wihumane.org/behavior/ask-the-experts/cat-behavior/enrichment-for-your-cat
- Project Bay Cat. A cooperative effort between Sequoia Audubon Society , the Homeless Cat Network and Foster City municipal government to humanely manage feral cats along the scenic Bay Trail in California. This area includes habitat for the endangered California Clapper Rail. A “tool kit” for others who wish to take similar action can be obtained free from firstname.lastname@example.org.
LINKS TO ONLINE RESOURCES
National Audubon Society
Reducing Threats from Cats
- Ash, S.J., and C.E. Adams. 2003. Public preferences for free-ranging domestic cat (Felis catus) management options. Wildlife Society Bulletin 31:334-339.
- Castillo, D., and A. L. Clarke. 2003. Trap/neuter/release methods ineffective in controlling domestic cat “colonies” on public lands. Natural Areas Journal 23:247-253.
- Carss, D.N. 1995. Prey brought home by two domestic cats (Felis catus) in northern Scotland. Journal of Zoology, London 237:678-686.
- Churcher, P.B., and J.H. Lawton. 1987. Predation by domestic cats in an English village. Journal of Zoology 212:439-455.
- Clarke, A.L., and T. Pacin. 2002. Domestic cat “colonies” in natural areas: a growing exotic species threat. Natural Areas Journal22:154-159.
- Coleman, J.S., and S.A. Temple. 1993. Rural residents’ free-ranging domestic cats: a survey. Wildlife Society Bulletin 21:381-390.
- Dunn, E.H., and D.L. Tessaglia. 1994. Predation of birds at feeders in winter. Journal of Field Ornithology 65:8-16.
- Eberhard, T. 1954. Food habits of Pennsylvania house cats. Journal of Wildlife Management 18:284-286.
- George, W.G. 1974. Domestic cats as predators and factors in winter shortages of raptor prey. Wilson Bulletin 86:384-396.
- Hagood, S. 2000. Cats and Wildlife. Wildlife Tracks 6(2). (quarterly publication of the Humane Society of the United States).
- Lepczyk, C.A., A.G. Mertig, and J. Liu. 2004. Landowners and cat predation across rural-to-urban landscapes. Biological Conservation115:191-201.
- Mead, C.J. 1982. Ringed birds killed by cats. Mammal Review 12:183-186.
- Patronek, G.J. 1998. Free-roaming and feral cats–their impact on wildlife and human beings. Journal of the American Veterinary Medical Association 212:218-226.
- Pearre, S. Jr., and R. Maass. 1998. Trends in the prey size-based trophic niches of feral and House Cats (Felis catus) L. Mammal Review 28:125-139.
- Turner, D.C., and P. Bateson. 2000. The Domestic Cat: The Biology of its Behavior. Second Edition. Cambridge University Press.
- Woods, M., R. A. McDonald, and S. Harris. 2003. Predation of wildlife by domestic cats (Felis catus) in Great Britain. Mammal Review33:174-186.
The authors of this paper are members of the Wisconsin Bird Conservation Initiative Issues Committee:
Scott Diehl – Director, Wisconsin Humane Society Wildlife Rehabilitation Center; WBCI Issues Committee Co-Chair.
Karen Etter Hale - WBCI Chair; Director of Community Relations, Wisconsin Audubon Council.
William Mueller – Director, Western Great Lakes Bird & Bat Observatory; WBCI Issues Committee Co-Chair.
Undergoing revision, September 2015.