Cats and Birds: an Increasing Problem

 

(This 700th column was first published in the August 29, 2004 issue of The Buffalo Sunday News.)

 

I have occasionally expressed concern in these columns about the effects of both pet and feral or free roaming housecats on other wildlife. In response I received the following letter from a reader who asked not to be identified:

 

"A while back one of your articles listed cats as the worst predators of birds. I found the enclosed bit of information in a book by Walter Chandoha in 1963 [evidently Walter Chandoha's Book of Kittens and Cats]:

 

"Cats: They are everywhere efficient rodent exterminators as required. They catch mice and rats for man -- man feeds them. It's a good relationship. Admittedly, they catch some birds too. But actually cats are not nearly as proficient at catching birds as is generally believed. The Audubon Society once printed a list of enemies of birds in this order:

 

1.       Disease

 

2.      Automobiles

 

3.      Weasels

 

4.      Humans

 

5.      Parasites

 

6.      Hawks

 

7.      Starvation

 

8.      Cats

 

"So, if cats are to help man by hunting for rodents, we must expect also to lose some birds. When I hear people complain of the way birds are bothered by cats, I feel compelled to remind them that man is not without fault in this respect either. I am reminded of a piece of dialogue I once read somewhere: 'That horrible cat caught another sparrow today,' said the duchess to the duke as she sat down to her quail and he to his pheasant.'"

 

I find no reference in my writing to cats as "the worst predators of birds" but I have recently read Ellen Perry Berkeley's well-written Maverick Cats: Encounters with Feral Cats which makes a better case for my correspondent than does Chandoha.

 

My correspondent quotes old data. Here are the best current estimates I find of birds killed annually through non-natural causes:(Curry and Kerlinger; Drennan; Holmstrom 1998; Sagrillo 2003; USFWS; Winter)

 

  1. glass windows in homes and commercial buildings:   97 to 976 million

 

  1. electric power lines: 130 to 174 million

 

  1. hunting:  over 100 million

 

  1. cars and trucks:  60 to 80 million

 

  1. agriculture (harvesting and pesticides):  67 million

 

  1. lighted communication towers:   4 to 10 million

 

I find no data on health-related causes of avian death, but I suspect that those numbers would head the list. Weasels make no list of which I am aware.

 

This leaves us with the question: How high on the list should birds killed by housecats appear?

 

The Audubon Society now estimates 100 million bird kills per year by cats(Drennan) which would place them fourth, but a variety of resources suggest that its estimate is far too low.

 

University of Wisconsin Professor Stanley Temple's careful analysis provides a best estimate of 39 million birds killed by cats each year in Wisconsin alone.(Coleman and Temple) If we consider Wisconsin representative of this country, we can extrapolate from those figures on the basis of area to give 2.5 billion birds killed by cats annually in the United States.

 

Too high? Perhaps but some suggest that Temple's data would even underestimate the rest of the nation because his is weighted toward rural communities while city cats are far more common today. Still, even 40 percent of that estimate would place cats at the top of the list of contributors to bird fatalities. And we have another carefully designed study that also indicates how serious is the toll of birds killed by cats.

 

Christopher Lepczyk and his colleagues at Michigan State University surveyed property owners along 75 miles of southeastern Michigan highways.(Lepczyk, Mertig, and Liu 2003) The responses indicate that there were between 800 and 3100 cats along those roads and that they killed between 16,000 and 47,000 birds there during a single breeding season. If you extrapolate those figures over Michigan's 120,000 miles of highway, you find that between 25 million and 75 million birds are killed by cats in Michigan during the summer months alone. Lepczyk's study clearly supports Temple's findings.

 

Whether or not you agree with those findings, I hope that you will see that cats pose a serious problem for birds.

 

Now let me restate my position. I consider myself a reasonably serious birder, but I also like cats. I admire both their grace and their independence; however, I believe that, other than barn cats, they should be kept indoors. My position is in agreement with that of the National Audubon Society(Drennan) and American Bird Conservancy.(Winter)

 

Pet cats kept indoors are healthier, they avoid the traffic accidents that claim 1.5 million cats each year and they live longer.

 

Whenever a cat steps outside it reverts to its inborn compulsion to hunt. It is far better to have it make passes at birds through your windowpane than from your bushes.

 

I will address the trap/neuter/release program in an upcoming column.-- Gerry Rising

 

Literature Cited

 

Coleman, John S., and Stanley A. Temple. 2004. On the prowl. Wisconsin Natural Resources Magazine [cited 2004]. Available from www.wnrmag.com/stories/1996/dec96/cats.htm.

Curry, Dick, and Paul Kerlinger. 2004. What kills birds? [cited 2004]. Available from www.currykerlinger.com/birds.htm.

Drennan, Susan Roney. 2004. Cats. National Audubon Society [cited 2004]. Available from www.audubon.org/local/cn/98march/cats.html.

Holmstrom, David. 1998. Fur flies over rising feline population. Christian Science Monitor, June 3, 1998.

Lepczyk, Christopher A., Angela G. Mertig, and Jianguo Liu. 2003. Landowners and cat predation across rural-to-urban landscapes. Biological Conservation 115:191-201.

Sagrillo, Mick. 2004. Putting wind power's effect on birds in perspective 2003 [cited 2004]. Available from www.awea.org/faq/sagrillo/swbirds.html.

USFWS. 2004. Cats and birds: a deadly combination [cited 2004]. Available from migratorybirds.fws.gov/issues/cats/catlinks.html.

Winter, Linda. 2004. Cats indoors. American Bird Conservancy [cited 2004]. Available from www.abcbirds.org/cats/.

-----. 2004. Domestic cat predation on birds and other wildlife [cited 2004]. Available from www.abcbirds.org/cats/predation.pdf.

 



In organizing this column I sought information from a number of sources. Here are some of the e-mail messages I received. I think that they all make interesting reading:

Liz Day:

Something I have often thought about the cat thing is that it seems to be about people's sympathies.

I gather (?) that many of the feral cat colony people have worked at shelters where they have seen hundreds of cats euthanized and their bodies disposed of. This has sensitized them to the suffering of unwanted cats. So when bird people tell them that more cats are bad for birds, even if they believe this is true, they don't feel it's as important, because their sympathies are with the cats. They had to pet these animals and then watch them die.

People don't keep wild birds as pets, so they don't know them personally the way they do cats, and they aren't really aware of what's going on in their lives so they can empathize (to know this, you would have to recognize an individual bird and be able to see what it does all day). They certainly don't see them die. Hardly any of the birds killed by cats are ever seen. If, instead, there were a pile of bird bodies to match the pile of cat bodies, this would have a huge impact on people's perception of the situation. All the heart-rending stories -- fledglings that are killed just as they leave the nest after weeks of work by the parents.... exhausted migrants who made it through a hundred perils only to be nailed by a cat when they stop to rest.... etc.... are things most people never observe. Everyone has seen stray cats.

I guess you could say this about a lot of things that go on in nature, but this seems to me like one of the more cogent examples.

Separately:

Also, I like the angle in the last paragraph of the cat entry of the rec.birds newsgroup FAQ, which I append below.

Are domestic cats Satan? -- A Non-judgmental Attempt at Consensus.

Many human activities lead to environmental damage in one degree or another. We clear, farm, flood, drain, divide, and build upon our surroundings with alacrity. We have also begun to realize that we can take steps to minimize the damage we do........

One way human beings damage the environment is by breeding animals to suit their own purposes. An example of such an "artificial animal" is the domestic cat, which provides affection and companionship for its owner and sometimes reduces domestic pests; unfortunately, it also hunts wild birds with little regard to its own food needs. Some domestic cats probably do little damage to wild birds. Others have single-handedly sent entire species into extinction.

If you own a cat, you can take steps to diminish its take. You can keep it indoors... Perhaps those steps will have little impact; perhaps your cat will only kill one fewer bird during its lifetime than it would have otherwise. Remember that there are billions of cats in the world, and, for example, only a few hundred Kirtland's Warblers.

Invocations of "the survival of the fittest" are not relevant here. Perhaps many birds are not competent to compete with housecats, or DDT, or highway construction programs. Nevertheless, we wish to preserve those birds because they pre-date their human-assisted competitors, because they represent irreplaceable parts of our world, and because they are beautiful.

Separately:

Joe: I read your email about the article you wrote about the effects of cats on bird population. I happen to own a cat and I feel strongly that cats should not be allowed to roam outside the home. Besides the effects on the wildlife, these cats suffer greatly from disease, illness and injuries that significantly reduces their life span. I can't tell you how many cats I have seen on the road side, evidently the result of being hit by a car. If cat owners were really concerned about their pets, they would not allow them out. This will save both wildlife and their pets. Maybe those who own cats would respond more positively if they understood the effects of their actions on their own pets.


Lance Laviolette, Montreal, Quebec:

An excellent starting reference is the University of Wisconsin Cooperative Extension Service web page: "Cats and Wildlife: A Conservation Dilemma," by John S. Coleman, Stanley A. Temple, and Scott R. Craven. The URL is wildlife.wisc.edu/extension/catfly3.htm. There are plenty of references to follow up on at the site.

The study that is most used as a benchmark is by P. B. Churcher and J. H. Lawton. Both biologists at the University of York in England, they studied this problem and reported their findings in 1987 in the Journal of Zoology. They carefully monitored all the prey caught by cats in an English town for a period of a year. At the end of that time they extrapolated from their findings to estimate that the approximately 6 million cats in Britain (about 2/3 domestic and 1/3 feral) kill approximately 100 million small mammals & birds annually. Of these approximately 36% were birds & 64% mammals. The figure I have estimates the U.S. cat population at approximately 60 million.

General bird mortality estimates from human activity in the U.S can be found at birds.fws.gov/mortality-fact-sheet.pdf. The ranges are rather broad and are derived from a number of different studies. To summarize the maximum numbers in decreasing order:

Window collisions: as high as 976 million
Cats: as high as hundreds of millions
Powerline collisions: as high as 174 million
Poisoning: at least 72 million
Automobile collisions: as high as 60 million
Communication tower collisions: as high as 50 million
Oil and wastewater pits: as high as 2 million
Fisheries bycatch: as high as hundreds of thousands

They do indicate that habitat loss and/or degredation is the greatest threat to birds and other wildlife.

Two more studies of cats impacting birds:

* In the United States in a year-long study published in Nature, (Crooks, K.R. & M. E. Soule (1999) Mesopredator release and avifaunal extinctions in a fragmented system. Nature 400: 563-566), Crooks & Soule found an annual kill rate of 24 rodents, 15 birds and 17 lizards per cat (i.e. 56 animals/year).

* In a study in California (1998, Texas A & M University) comparing two parks with similar grassland habitats (one with cats present, and another with cats absent) C.C. Hawkins found that there were twice as many birds present in the park with no cats compared to the one with cats. Moreover ground-nesting species such as Thrashers and Quail, which were common in the non-cat areas, were completely absent from areas where cats were present.

Separately:

Where did this guy come up with weasels? Beats me but you know how the 'dreaded' cat thread goes. The last time this thread really heated up on BIRDCHAT was 1997. At that time Ellen Paul, University of Maryland, sent a long email which was comprised of a report by John S. Coleman, Stanley A. Temple and Scott R. Craven entitled A Conservation Dilemma. I can send you the email if you haven't seen it or picked it out of the BIRDCHAT achieves. Also, below I've listed a few more cases of cats impacting bird populations, basically island situations where they were introduced. Details are found on the web:

* On the islands around New Zealand such as Little Barrier Island
* Marion Island in the South Indian Ocean
* Jarvis Island
* MacQuarie Island
* Ile aux Cochons in the Crozet Islands
* Kerguelen Island in the South Indian Ocean

Another interesting web reference, dealing with the impact of feral cats in Australia, can be found at www.deh.gov.au/biodiversity/invasive/ferals/cat/impacts/pubs/impacts-feral-cats.pdf


Laura Erickson, Duluth, MN:

That list was put together in 1963. Weasels are the number 3 killer of birds? If they ever were, they certainly aren't now. The current numbers are based on the best scientific information currently available, as researched by several independent institutions and scientists. The numbers in '63 may have been someone's best guess, but based on the prominence of weasels, I suspect none of them were based on an unbiased and scientific evaluation.


Richard Guthrie, Poughkeepsie, NY:

Interesting; I, too, have included a little bit about cats in an article for Poughkeepsie Journal to come out this Sunday. Even though its an upstate newspaper, I mentioned the feral populations that prowl the State Parks on Long Island and the people who feed the cats. There is a segue in there. I'm ready for the onslaught (I think).


Heath Wakelee, Granite Bay, CA (near Sacramento):

When dealing with this issue I generally break it down as there are about 30 million (?) cats in the USA and half of those are "house" cats so that leaves 15 million that spend at least some time outside. Most cat owners will admit to their cat killing at least one bird every two months so 15 x 6 is 90 million birds killed by cats each year. A conservative estimate and a very big number.

Another good (provable) number is that there are 143 million mourning doves killed each year by hunters. That would help account for some of the high risk numbers associated with humans taking of birds.


Jeff Reed, Olean, NY:

I live on an old dairy farm and my neighbors encourage cats for all the reasons mentioned (rodent predation mainly). I discourage them whenever possible but sometimes they get in under my radar. Judging by their trophies, they seem mostly interested in meadow voles and mice.

I don't doubt they would take birds if they could get them but since they like to be around humans, they would probably take the birds that like to be around humans - Robins, Starlings, Blue Jays if they're lucky. However, a friend reported that her cat got a Brown Thrasher...bummer.

I've never seen a cat in the woods or even in my fields once the grass gets more than a few inches high and I've never seen them near my Bluebird boxes which surprises me a little. The crows generally know when they're around and alert everybody else but that may not help the slowest fledglings.

I think towers and cars are much more lethal, especially to migrants.


Dick Rosche, East Aurora, NY:

I agree with you 100%. The Am. Bird Conservancy has a campaign on about keeping cats indoors. I just got a lot of stuff from them and intend to eventually use it all in NATURE PRESERVES. The feral cat problem is a BIG one. I have noticed over the years that it is the people who own cats and let them loose outdoors who are the main culprits who always say that it is cats nature to be outside to catch mice, birds, and what have you. They say you can't change a cats nature. Hog wash. We just had a cat put to sleep in March that lived inside the house for 14 years; his paws never touched the ground! And he was a happy cat!


Eric Salzman:

We have a 10.5 acre property on Weesuck Creek and Shinnecock Bay in Eastern Long Island, most of which is now a dedicated reserve. And we are opposite a 100 acre preserve on the other bank of the creek. Both property are a mix of wetlands and wooded upland with a small amount of open meadow. Both properties have extensive bird lists (221 species on this side) and a fairly good list of breeding birds. What is missing on both sides on the creek are the ground nesters and ground feeders which used to be common here and have now been eliminated by marauding cats. These include Whip-poor-will and N. Bobwhite plus many passerines (Wood Thrush, Brown Thrasher, Eastern Towhee, Black-and-white Warbler, Blue-winged Warbler, Ovenbird). These birds are simply not adapted to the predatory pressure of free-roaming cats and disappear from any area where cats roam. Unfortunately, although the issue of unleashed and stray dogs has been dealt with (because of the threat to children I am sure), nothing is done about cats.

Separately:

Thought you might be interested in Temple's reply to my inquiry.

From: STANLEY A TEMPLE

My students and I have done some of the research that gets cited frequently, but if you want to go to the best overall source of information on the issues, go to Linda Winter at American Bird Conservancy. She coordinates their Cats Indoors! program and really stays on top of the latest developments.


Mike Morgante:

The barnyard cats may get more rodents than birds, but what about suburbia and the cities where the cats have more birds to prey on? I think that is where the toll is taken the most.


Bob McKinney:

I am in total support of your campaign against cats, feral or tame. I wish we had some concrete figures on the damage done by cats, It must be terrible. This issue reminds me of the Trumpeter Swan issue in that people get so emotionally involved that they can't see the reality of the matters. Chita and I have a few acres of overgrown farmland in the hills of northern Steuben County, south of Naples. We discovered late last summer that a neighbor must have at least 12 cats which are allowed to roam all of the time. We do see them on our property. I am still recovering from very complicated hip surgery last winter and am still hobbling around on crutches. As soon as I graduate to a cane or walking stick, and can carry an animal trap, I am going after those cats.


Jay Greenberg:

I think pesticides have to be one of the major killers of birds, but they were not on Chandoha's list even though at that time, DDT was very much in the news thanks to Rachel Carson. I think this omission casts serious doubt on the credibility of the list.


Linda Winter:

I have recently updated the fact sheets from our Education kit - check out "Cat Predation on Birds and Other Wildlife" and "Managed" Cat Colonies - The Wrong Solution to a Tragic Problem" at . The American Veterinary Medical Association has a Position Statement on Abandoned and Feral Cats, but in no way do they endorse TNR or oppose it. They make simple statements on how it should be done if someone is going to do it, although what they suggest is still inadequate, almost none of the cat feeders I know of actually follow AVMA's guidelines. They even argue against removing cat colonies from locations where endangered species are present that we know cats kill unless they are presented with proof that one of the cats they were feeding actually did the killing. I could give you so many examples of where TNR has continued for 10 - 15 years and counting. If it worked so well, why are people still feeding cats in the same location? Feel free to run your article by me. See also the state pages on the web site for FL, CA, and HI, although they are a bit outdated.


Sally Jean Cunningham, East Aurora, NY:

Another angle (on the side of keeping them in) is: Cats who go outside regularly live much shorter lives than indoor cats. I think I had an average of 2-year average lifespan for indoor-outdoor cats. So that is a reason to keep them in...but it doesn't solve the rodent matter!

Even if we do validate the importance of cats in rodent control, the justification the farms use, I would always want to add: A healthy well-fed neutered cat is the only kind to have in a barn if you are doing that. Neutered cats stay there rather than roam for sex, and healthy cats have the energy to hunt well. (Cats do not hunt for hunger but out of instinct.)

Personal observation: Cats I have had who were wild and than I tamed ..continued to hunt and lay rodents on the deck but they have not lain birds there. There is the argument of the birds who are caught were the weaker or sick ones.

From a humane point of view, the neuter-and-release program is dignified for those animals who have no other hope of life, and for decreasing the numbers. (Even for a birder viewpoint, much better than just having thousands of cats result from an unneutered couple!) I personally believe that every cat should have an indoor home, and a few - taken from an outdoor life, in a real country location - require some outdoor time. I have one out of four who is crazed if he doesn't go out for awhile daily. I avoid his outside time falling when the spring baby animals are just learning, and at dawn and dusk.


David Klauber

I have some thoughts on the matter. The unidentified reader seems to be as interested in being cute (duke and duchess - really, that must have come from the 1800's) as in contributing in a meaningful manner. I do agree that having a cat on a farm or country house does control the mouse population around the house.

Assuming that Walter Chandoha's statistics had some credibility, maybe a big if, given that cats are the subject and quite possibly objects of affection to the author, note the date is 1963 and undoubtedly the data was prior to that. I grew up on Long Island in the fifties and sixties, and there were some wild cats, but a lot more habitat and birds. There is certainly much less habitat, more people, and more pets than 40 years ago. To my knowledge you did not have the feral cat colonies established by "cat lovers" in state and county parks that you do today.

Cats indeed may not be the largest source of bird mortality, but it would seem that they are one of the more controllable sources, as opposed to radar towers, certain diseases, and road kills. Hawks, starvation, weasels, and maybe some non-imported diseases could reasonably fall under the balance of nature, needing no intervention. At a minimum the establishment of feral cat colonies (Jones Beach, Montauk Point, etc.) in our parks seems to be controllable. Jones Beach, with mostly ground vegetation and low bushes, surely must be an inappropriate place to feed a large group of cats, yet it goes on without interference by authorities.

One more observation on neutering wild cats. Within the last year in our local newspaper Newsday a professed cat lover who attempts to neuter wild cats says it is very difficult to catch truly feral or wild cats, as they are wary, and they don't make good pets. Again, this from the cat lover.

Separately: You may be right about the mouser effect, and they don't take rats as far as I know, but I have some personal experience with cats and mice. Years ago for one winter I lived in an old house in Switzerland that was used often by construction workers, and had burlap on the walls. A mouse or mice would run between the burlap and the walls, often right over my head. I borrowed the cat of the girls upstairs for one night. The cat went after the mouse, occasionally falling off the burlap onto my head. I don't know if it caught the mouse, but we were never bothered by it again. I think the smell of the cat may have helped, but I'm not sure. In another instance a woman on Mallorca, Spain had cats to keep down the rodent population in her farm house. The locals killed the cats for whatever reason, and her house was subsequently overrun by mice - not that there weren't other options. Her dogs (which the locals did not kill) went after the rats but not the mice. So I think they can be useful at times, but I still don't care for them much.


Bob Beal, Middlesex, NY:

I've had a female Yellow Warbler hanging around my feeders, I've yet to see it feed on suet, but I've decided to try mealworms. Anyone else had any luck with feeder warblers? I know Pine and Yellow-rumped will occasionally come, and I remember many years ago a Painted Redstart was coming to peanut butter in Dansville, Livingston County during December and part of January until the neighbor's cat got it! Ce'st la Vie!


Joan Dziezyc:

I felt the same way about neuter-release programs when I first heard about them, but there is a rationale for doing things that way.

Now, if we could just get everyone to neuter their pets and not allow them to roam...we'd solve lots of problems....

Linda Winter: We are very pleased to announce that the Florida Fish and Wildlife Conservation Commission (FWC) has launched a new stewardship project as a key strategy in implementing FWC's policy to, "protect native wildlife from predation, disease and other impacts presented by feral and free-ranging cats." The program encourages cat owners to keep their cats indoors, to spay or neuter their cats before a litter is produced, and to never abandon cats. The new education materials include a color poster, print, radio and TV Public Service Announcements (PSAs) and a Power Point slide presentation. All materials can be downloaded from www.MyFWC.com/cats. Go to "Popular Links" and click on "Domestic Cat Information."

The materials were produced in collaboration with American Bird Conservancy (ABC). We congratulate the FWC for taking a national lead on this important conservation and animal welfare issue. FWC has distributed ABC's Cats Indoors! brochures and other materials to veterinarians, humane societies, animal control agencies, and the general public for years. The development of state-specific materials is the next logical step in that education effort. We are very pleased to be a partner in this project and encourage other state wildlife agencies to conduct similar education projects. We also encourage our campaign supporters in Florida and the media to assist in this education effort by using and publicizing these materials.