Video recordings of Brown-headed Cowbirds (Molothrus ater) at the nests of grassland birds are of interest because relatively few such observations exist. We documented 7 events where cowbirds removed nest contents at 6 active nests and 1 empty nest. Among 6 attended nests, cowbirds arrived at the nest an average of 3.8 min (range 0.7–11.6 min) after the host species left. Cowbirds removed nest contents during the early morning (mean = 3.9 h after sunrise, SE = 0.3 h, n = 4) or late afternoon (mean = 13.1 h after sunrise, SE = 0.4 h, n = 3), taking an average of 0.7 min (range 0.4–1.1 min) to remove nest contents. Cowbirds sequentially moved nest contents away from the nest in 4 of the 7 events taking an average of 3 trips (range 2–4) to do so. Among 6 attended nests, cowbirds left the nest an average of 3.4 min (range 0.5–10.7 min) before the host species arrived back at the nest. Of the 6 active nests, cowbird damage of nest contents directly resulted in the failure of only 1 nest. Three nests went on to fledge the remaining host young, while 2 failed due to other causes. Our observations add to a growing number of video-recorded behaviors of brood parasites that can provide data for better testing hypotheses about nest destruction behavior.

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