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CATS vs. BIRDS: COUNTERING THE PREDATION ISSUE

RESOURCES

Addressing the Wisconsin Study

Ferals, Ferals Everywhere (see section “Countering the Predation Issue”)

Feral Cats on the Firing Line

How Much of an Impact Do Cats Make on Wildlife?

Living in the Grey Zone

Pennsylvania Animal Alliance Position Paper (see pages 5-10)

Understanding Cats and Predation

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PREDATION STUDIES

Wildlife biologist Roger Tabor, who is considered by his peers to be one of the world’s leading experts on cats and has studied feral cats for over 30 years, is quoted as saying, "The clear leading animal that’s really putting wildlife at risk is the human population. We just don’t like to acknowledge that it is our fault. It’s not a case of the cat being the worst offender. It isn’t even remotely the worst offender. It’s us." (Living in the Gray Zone, Estelle Munro, October 2003).  In The Wild Life of the Domestic Cat, (Arrow Books, 1983), Tabor states, “In biological systems it is insufficient merely to have found one animal will eat another, that after all is what predators do - [the more important question is whether it] is predation within normal limits”.  Researchers must ask (1) Does the species exhibit predatory behavior?, and (2) How much does the predatory behavior adversely impact prey population?

The two studies most-often quoted by bird conservation organizations, such as the American Bird Conservancy, as supporting the notion that cats are a threat to bird populations are Churcher and Lawton (1989) and Coleman and Temple (1993).  However the Churcher and Lawton study is extremely problematic, and “Churcher himself is quoted in the newsletter Catnip (published by the Tufts University School of Veterinary Medicine) sounding a note of caution. ‘I’d be very wary,’ says Churcher, ‘about extrapolating our results even for the rest of Britain, let alone America.  I don’t really go along with the idea of cats being a threat to wildlife.’” (TNR: Past Present and Future, Ellen Perry Berkeley, 2004)  Likewise, Stanley Temple admitted in an interview with Jeff Elliot of the Sonoma County Independent in 1994, that the figures used in Coleman and Temple were not scientifically-based, but merely guesswork as part of a proposal for a study. 

Read “Ferals, Ferals Everywhere - Countering the Predation Issue”, by Nathan Winograd to find out why there is little science behind these two studies.

Studies that found cats were NOT to blame for declining bird populations include:

Errington, Paul L., 1936
Notes on food habits of southern Wisconsin house cats. Journal of Mammalogy 17:64-65
“Preying upon a species is not necessarily synonymous with controlling it or even influencing its numbers to any perceptible degree.  Predation which merely removed an exposed prey surplus that is naturally doomed is entirely different from predation the weight of which is instrumental in forcing down prey populations or in holding them at given approximate levels”

Coman, Brian J., and Hans Brunner, 1972
Food Habits of the Feral House Cat in Victoria. Journal of Wildlife Management 36 (3): 848-853
“Most references to predation by feral cats are unsupported by factual data” (848); “The common belief that feral cats are serious predators of birds is apparently without basis” (852-3)

Fitzgerald, B. M., and B. J. Karl, 1979
Foods of feral house cats (felis catus L.) in forest of the Orongorongo Valley, Wellington.  New Zealand Journal of Zoology 6:107-126
"Cats suppress populations of more dangerous predators such as rats and thus allow denser populations of birds than would exist without them."

Mead, C.J., 1982
Biologist Chris Mead “found no evidence that cats are impacting overall bird populations”

Tabor, Roger, 1993
Tabor found that “cats have low success as bird hunters”, and “the bulk of a feral cat’s diet is garbage, plants, insects, and other scavenger material” and therefore cats are “not impacting bird populations on the continents”

Berg, Robert, 1993
San Francisco SPCA report regarding quail population in Golden Gate Park, San Francisco
Biologist Robert Berg found that cats are not impacting quail populations in Golden Gate Park in San Francisco even though the quail nest on the ground.  In fact, any feral cat predation in Golden Gate Park would actually occur on the rat population in the park, increasing quail strength by lowering nest predation of quail by rats.

Moller, Anders and Erritzoe, Johannes, 2000
Universite Pierre et Marie Curie in Paris, June, 2000
Moller & Erritzoe examined birds killed by cats vs. those that met accidental deaths by crashing into windows. They examined the birds for various factors, the most significant of which was the health of the bird. They found that while windows were non-discriminating and killed healthy and sickly birds equally, the birds cats killed were significantly sicklier than those who crashed into windows, with 70% of them being slow movers and fledglings.  The conclusion of the study was the cats appear to be strengthening the bird population by ensuring that the fittest birds survive. (see “Ferals, Ferals Everywhere - Countering the Predation Issue”)

LaBruna, Danielle, 2001
Introduced Species Summary Project Domestic Cat (Felis catus), Columbia University, January 29, 2001
The Columbia study found that "reducing cats' effect on the ecosystem may actually have a negative impact upon some native species due to the possibility of 'mesopredator release effect' “. The study also recommended that we confront the cat population problem with a combination of methods: "enlist the ‘trap-neuter-return’ style of feral management and combine it with incentives for owners to sterilize their pet cats."

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SCAPEGOATS FOR DECLINING BIRD POPULATIONS

Gary J. Patronek, VMD, Ph.D. Tufts University wrote in a Letter to Editor, Journal of the American Veterinary Medical Association, Vol. 209, No. 10, November 15, 1996:

"If the real objection to managed colonies is that it is unethical to put cats in a situation where they could potentially kill any wild creature, then the ethical issue should be debated on its own merits without burdening the discussion with highly speculative numerical estimates for either wildlife mortality or cat predation. Whittling down guesses or extrapolations from limited observations by a factor of 10 or even 100 does not make these estimates any more credible, and the fact that they are the best available data is not sufficient to justify their use when the consequences may be extermination for cats.”

"What I find inconsistent in an otherwise scientific debate about biodiversity is how indictment of cats has been pursued almost in spite of the evidence."

If cats are not to blame, what are the causes of the declining bird population in some bird species?

Stanford University, Center for Conservation Biology (1993): Found it was environmental loss

National Geographic (1993): Linked declines to poisons in environment, particularly lawn care products

Worldwatch Institute (1994): Found that birds are in decline due to drought, habitat loss, over-trapping, and water pollution.  Cats were noticeably absent as factors.

Colorado Wildlife Dept (1994): Found the cause to be drought

University of Georgia (1998): Blamed forest fragmentation across Southern U.S. for decimating songbird population