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We report nine new records of Brown-headed Cowbird (Molothrus ater) parasitism on the Common Grackle (Quiscalus quiscula): six from Benson County, North Dakota, and three from Delta Marsh, Manitoba. These observations represent 30% of the total number of records of parasitism on this host. Parasitism frequencies were 0.8% of 727 nests in North Dakota, and 4.0% of 75 nests in Manitoba. The data from Manitoba, combined with previous data from this location (Neudorf and Sealy 1994), yields a parasitism frequency of 3.4% of 119 nests examined. These parasitism frequencies are the highest recorded for the Common Grackle.