Technical note: comparison of simulated ground nest types for grazing/trampling research.

Abstract

Ornithologists often use simulated nests consisting of game bird or domestic poultry eggs to study nest survival. Researchers investigating cattle trampling of ground nests have sometimes used clay targets instead of actual eggs to avoid the confounding effects of nest depredation. To determine whether livestock respond similarly to clay targets and egg nests, we compared inadvertent trampling and intentional disturbance of clay targets versus clutches of 3 pheasant eggs by Angus X Holstein heifers. Overall trampling levels for clay target- and egg-nests were similar (35 and 36%, respectively). Cattle noticed and responded to both types of nests. When noticed, simulated nests were kicked, sniffed, licked, or picked up in the mouth. Cattle disturbed an average of 25% of the clay targets and 8% of the egg nests during 4 trials. Our results suggest that cattle are as likely to inadvertently trample egg nests as they are clay targets, but targets are more likely to attract attention and are therefore disturbed more often than egg nests. The greater likelihood of intentional disturbance of clay targets by cattle reduces the confidence of extrapolating the fate of this type of simulated nest to that of actual nests.