Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub

    Description

    The effects of brood parasitism by the dwarf race of the Brown-headed Cowbird (Molothrus ater obscurus) on the nesting success of the Abert's Towhee (Pipilo aberti) in the lower Colorado River valley were studied. The frequency of cowbird parasitism varied significantly with time of season. The laying season of cowbirds paralleled that of migratory songbirds, but began a month later than that of the sedentary Abert's Towhee. After an influx of breeding cowbirds, 44% of towhee nests were parasitized. Egg ejection by adult cowbirds caused towhee clutches to decline significantly from a laying average of 2.9 eggs to 1.7 eggs at hatching. The probability of nesting success declined from 0.278, before cowbirds arrived on the breeding grounds, to 0.046 for all parasitized nests. The lack of a significant difference between daily mortality rates of nonparasitized nests before and after cowbirds started breeding indicated that the reduced success of late towhee nests was primarily due to cowbird parasitism. The success of cowbird eggs in towhee nests was also low, suggesting that towhees may not be favorable hosts.

    Publication Notes

    • You may send email to rmrspubrequest@fs.fed.us to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

    Citation

    Finch, Deborah M. 1983. Brood parasitism of the Abert's Towhee: Timing, frequency, and effects. The Condor. 85(3): 355-359.

    Keywords

    Brown-headed Cowbird, Molothrus ater obscurus, Abert's Towhee, Pipilo aberti, brood parasitism

    Related Search


    XML: View XML
Show More
Show Fewer
Jump to Top of Page
https://www.fs.usda.gov/treesearch/pubs/35603