I know I'm late with this request--several weeks ago the topic of garter snakes eating birds came up, and I said I recalled reading an article about such behavior. I finally went through my old herpetological journals and found it.
"Predation of White-crowned Sparrow Nestlings by the Western Terrestrial Garter Snake in San Francisco, California" by David K. James, Lewis Petrinovich, Thomas L. Patterson and Anthony H. James. It was publishe din Copeia 1983, No.2. Here's the abstract:
In studies of White-crowned sparrows (Zonotrichia leucophrys nuttalli) in San Francisco, California, snakes (Thamnophis elegans) were often seen preying on nestling birds. Petrinovich and Patterson (In prep.) suggested that T. elegans might be a major predator of white-crowned sparrow nestlings in the San Francisco population. In various parts of its range Thamnophis has been reported to feed on a wide variety of prey: fish, slugs, reptiles, insects, rodents, leeches, lizards and salamanders (Tanner, 1949; Fitch, 1965; Fleharty, 1967; Carr, 1976; Arnold, 1977, 1980; Arnold and Wassersug, 1978). Few populations of T. elegans have been reported to have a large percentage of mammals in their diet. Whit and Kolb (1974) found that 26.9% of the diet of T. elegans found along a stream in the Sierra Nevada Mountains in California consisted of the meadow mouse (Microtus sp.) although this population primarily feeds on fish. Fox (1952) reported that a population found in San Mateo County, Ca.lifornia fed mainly on Microtus. Gregory et al. (1980) found a population of T. elegans in British Columbia to feed on mammals. Fox (1951) reported that T. elegans were seen taking young sparrows (Zonotrichia leucophrys) and Campbell (1969) observed T. elegans taking pelagic cormorant nestlings (Phalacrocorax pelagicus), pigeon guillemot nestlings (Cepphus columba), northwestern crow eggs and young (Corvus brahcyrynchous) and glaucous-winged gulls nestlings (Larus glaucescens). It seems that most populations of T. elegans do not feed primarily on mammals or birds. This paper presents data regarding the prevalance of snake predation on two populations of white-crowned sparrow nestlings in San Francisco, California.
The paper goes on to describe observations of western terrestrial garter snakes found in the sparrow nests, eating nestlings; sparrow parent reaction to the snakes, and possible correllations between snake predation of nestlings and sparrow reproductive rates.
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Chris McMartin
www.mcmartinville.com
I'm Not a Herpetologist, but I Play One on the Internet
