Brown Thrasher (Toxostoma rufum) Science Article 6
abstract
Rates of brood parasitism by Brown-headed Cowbirds Molothrus ater on nests of Brown Thrashers Toxostoma rufum in south-central North Dakota ranged from 3% to 18% from 1984-1986. The average observed rate of parasitism, 12%, was higher than typically reported for Brown Thrashers. We conducted an experiment to determine if these high observed rates of parasitism were a result of unusually high rates of parasitism by cowbirds or unusually low rates of rejection by thrashers
Carola A. Haas et al, The Condor 100:535-540