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Rejection of cowbird eggs by crissal thrashersAuthor(s): Deborah M. Finch
Source: The Auk. 99: 719-724.
Publication Series: Miscellaneous Publication
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DescriptionAlthough the "dwarf" race of the Brown-headed Cowbird (Molothrus ater obscurus) is sympatric with the Crissal Thrasher (Toxostoma dorsale) in the lower Colorado River valley, I observed no parasitism in 15 thrasher nests. To determine whether or not the absence of cowbird eggs was caused by egg rejection, I experimentally parasitized nine thrasher nests. Cowbird eggs were ejected by thrashers at all experimental nests. To test the prediction that ejection or absence of cowbird eggs reduces nesting mortality, I compared thrasher nesting success to that of a sympatric accepter, the Abert's Towhee (Pipilo aberti).
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CitationFinch, Deborah M. 1982. Rejection of cowbird eggs by crissal thrashers. The Auk. 99: 719-724.
KeywordsBrown-headed Cowbird, Molothrus ater obscurus, Crissal Thrasher, Toxostoma dorsale, Abert's Towhee, Pipilo aberti, egg rejection
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