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The Center for Native Grasslands Management

Title: First record of brown-headed cowbird parasitism on Cassin’s sparrow in Oklahoma
Year: 2009
Author(s): Van Els, P., Cooper, B. S., Doxon, E. D.
Source Title: Bulletin of the Oklahoma Ornithological Society
Source Type: Journal
pages: 13-15
Original Publication: http://  
Abstract: Cassinís Sparrow (Aimophila cassinii), an emberizid with a distribution limited to the shrub-grasslands of the southwestern U.S. and northern Mexico, has been reported to be an infrequent host of the brood parasite, Brown-headed Cowbird (Molothrus ater). We present the first documented records of parasitism on Casssinís Sparrow by cowbirds for Oklahoma. Eleven of 45 (24.4%) Cassinís Sparrow nests found during 2006Ė2008 were parasitized by cowbirds. This may indicate that Cassinís Sparrows are more frequently parasitized than previously thought or that this species experiences a higher rate of brood parasitism in the northeastern part of its range in Oklahoma. Reasons for locally increased parasitism rates may include small-scale geographic variation in host preference by cowbirds or variation in host nest availability due to the highly fluctuating nature of Cassinís Sparrow abundance.