We present digital recordings from video surveillance systems at nests of grassland birds. Video surveillance systems were used as part of grassland bird studies done in southwestern Wisconsin. The digital recordings archived here were used to document egg and nestling destruction by the Brown-headed Cowbird (Molothrus ater). Study sites were clustered near Mt. Horeb (43.0167°N, 89.7500°W). Four grassy field types were studied: continuously-grazed pasture, prairie, and cool- and warm-season grass fields.

We used video surveillance systems at nests to identify the nest predators in all the studies. We prioritized putting video surveillance systems on nests of obligate grassland birds, followed by facultative grassland birds, and finally generalist birds that occurred in the grasslands. In general, we used cameras with infrared light-emitting diodes (LEDs) that facilitated recording quality images under low-light conditions. We distributed cameras among fields to avoid clustering and we set up cameras at nests during or soon after the egg-laying stage ended to lower the chance for abandonment. Recording systems were attached to cameras with 25-m cables (following the protocol established by Renfrew and Ribic 2003). Each camera was mounted on a wooden dowel 3 – 38 cm above the ground. Cameras were 64 cm3 and placed 12 –25 cm from the nest, depending on the nest structure and surrounding vegetation. The field of view at these distances ranged from 414 to 1,320 cm3. Cameras were typically placed at or below the height of surrounding vegetation to avoid creating a potential visual cue for potential predators.

As part of data analysis for each study, we watched the digital recordings of all nests to document nest fate as well as any other events that resulted in loss of an egg or nestling and compiled this information in a master data file. We watched the digital recordings using VideoLAN VLC Media Player or DivX Player. For this study, we used any event (partial or complete nest predations, scavenging of unhatched eggs) from this master file that involved a Brown-headed Cowbird.

Description of the data and file structure

There are 7 video files with female Brown-headed Cowbirds removing eggs and/or nestlings from passerine birds nests. Each file name has the date of the event, species of passerine bird, and a short description of the event.

Sharing/Access information

Data were derived from the following sources:

• Byers, C. M., C. A. Ribic, D. W. Sample., J. D. Dadisman, and M. R. Guttery. 2017. Grassland bird productivity in warm season grass fields in southwest Wisconsin. American Midland Naturalist 178:47–63.
• Ellison, K. S., C. A. Ribic, D. W. Sample, M. J. Fawcett, and J. D. Dadisman. 2013. Impacts of tree rows on grassland birds and potential nest predators: a removal experiment. PLoS ONE 8(4):e59151. https://doi.org/10.1371/journal.pone.0059151.
• Renfrew, R. B., C. A. Ribic, and J. L. Nack. 2005. Edge avoidance by nesting grassland birds: a futile strategy in a fragmented landscape. The Auk 122:618–636.
• Ribic, C. A., M. J. Guzy, T. A. Anderson, D. W. Sample, and J. L. Nack. 2012. Bird productivity and nest predation in agricultural grasslands. Studies in Avian Biology 43:119-134.