rising@utzoo.uucp (Jim Rising) (12/07/89)
I promised myself that I'd stay out of this cat/bird controversy--but Denise has rekindled my interest. I originally posted an answer to the question, "What do I do with my cat if I want it outdoors and don't want it to kill birds." I suggested belling it; others suggested putting it on a leash--both constructive ideas that don't involve hurting the cat, but I got flamed as a cat hater. (For the record, I love cats, have a pet cat that I keep inside, and have always had cats.) I was told that my posting elicited a flame (I was hitting the "n" key on this subject by then) because "cats don't really bother birds". That's simply not correct. Some cats do little or no damage, but other are quite good bird catchers, etc. I live in the MIDDLE of a large city (Toronto) and the nextdoor cat catches Chestnut-sided, Black-throated Green, Myrtle and Bay-breasted warblers plus lots of yellowthroats and winter wrens. He is especially good at getting migrants, and I'm sure that I see only a portion of his catch. Denise raises the question as to the damage that that does to populations. I suspect that it is a fairly insignificant cause of mortality, but it would be very difficult to assess. But that was not the original issue. Sure, other things (such as destruction of wintering habitat; pesticides; flying into lighted buildings) may be more important, but the question was, how can I keep my cat or other cats from eating birds in the city? Denise also points out that there are many natural predators of these birds. Of course, but that again begs the issue. Domestic cats differ from "wild" predators (e.g. Blue Jays, opossums, raccoons) because these wild predators are limited by the prey that they can catch. House cats go home for dinner. This is important because it limits the DENSITY of predators. Back to conservation, I suspect that in North America today house cats play a MAJOR role in URBAN wildlife communities. They probably effectively extirpate ground nesting birds (in Toronto, things like ovenbirds and mourning warblers can no longer nest in parks or backyards), salamanders, lizards, catch many baby birds (e.g. cardinals, robins, grackles) both in the nests and after they fledge--in addition to extracting a toll on migrants. Cats also kill lots of rodents and squirrels (which I also like). In N.A. cats probably DO NOT have a major affect on global populations of birds. How about the Stephen Island wren? This species has (I think) the unique distinction of being the only species both discovered and extirpated by a cat. The lightkeeper on Stephen Island (off New Zealand) had a cat that collected all of the specimens of this species in 1894, and wiped the species out. It is one of 33 "forms" (probably species + subspecies) of birds that have been extirpated by cats--see figure on page 437 in "Ornithology an Ecological Approach" by J. Faaborg (1988). I cannot vouch for the details of these--but one other quote (from Welty, "The Life of Birds" (p. 541) substantiates the idea that domestic cats can have a deleterious impact on local avifauna. "In 1970 on Christmas Island in the equatorial Pacific, one colony of Sooty Terns...laid an estimated 600,000 eggs between May and August. Native Gilbertese collected and ate about 250,000 eggs. Great Frigate Birds ...preyed on the young chicks, and domestic cats killed and ate between 50 and 75 adult terns each night." and "The small island of Herokapare off New Zealand contained 400,000 birds before the advent of cats around 1931. Now there are only a few thousand birds left, and six species have disappeared entirely." I'll repeat (for what good it will do), I don't dislike cats, and think that it is silly to think of cats has having good and bad characteristics, but cats, and dogs, and rats, and goats, and cattle..., and many other symbiotes of people do real damage to wildlife, when left uncontrolled. Incidentally, although I have forgotten the exact source (unlike the above), I read recently that domestic cats kept indoors have an average life expectancy of 15-16 years. Domestic cats allowed to roam about outdoors have an average life expectancy of 2 years or less. Jim Rising -- Name: Jim Rising Mail: Dept. Zoology, Univ. Toronto, Toronto, Ontario, Canada M5S 1A1 UUCP: uunet!attcan!utzoo!rising BITNET: rising@utzoo.utoronto.bitnet