Abstract
Predation is the predominant cause of nest failure for the Brewer's Sparrow (
Spizella breweri breweri), a provincially red-listed shrub-steppe species that has experienced significant declines throughout most of its range. We monitored Brewer’s Sparrow nests and conducted an artificial nest experiment, in the South Okanagan Valley, British Columbia (B.C.), to investigate factors associated with nest predation. Avian predation of artificial nests was higher when nests were placed in smaller shrubs, set out earlier in the season and when corvid numbers were high. Predator imprints on clay eggs in the artificial nest experiment showed that rodent predation increased through the season. Results from real nests indicate that nest initiation date was also an important predictor of nesting success with more predation by all predators later in the season. Nesting density was lower at sites with more corvids, and much higher at similar sites with low corvid numbers. Our results suggest that Brewer's Sparrows select sites lower in avian nest predator activity and that this results in the effect of other predators such as rodent becoming more apparent.
Parent Publication
Keywords
artificial nests,
Brewer's Sparrow,
corvids,
depredation,
predator avoidance,
Spizella breweri breweri,
survival analysis,
timing
Citation
Kym Welstead, Pam Krannitz, Nancy Mahony. 2005. Using survival analysis of artificial and Real Brewer''s sparrow (
Spizella breweri breweri) nests to model site level and nest site factors associated with nest success in the South Okanagan region of Canada. In: Ralph, C. John; Rich, Terrell D., editors 2005. Bird Conservation Implementation and Integration in the Americas: Proceedings of the Third International Partners in Flight Conference. 2002 March 20-24; Asilomar, California, Volume 1 Gen. Tech. Rep. PSW-GTR-191. Albany, CA: U.S. Dept. of Agriculture, Forest Service, Pacific Southwest Research Station: p. 630-636
