Predation on Birds' Nests in Relation to Antipredator Aggression and Nest Density: An Experimental Study

Abstract

Artificial birds' nests containing 2 eggs were placed in 5 study plots (area 4 ha) at densities of 1 to 4 nests ha-' and exposed for short periods (1-3 days) to predation, mainly by Corvus corone cornix L. and Larus argentatus Pont. Predation rates were high (75 to 96 % on average in 6 experiments) and positively correlated with nest density in 4 plots. In the fifth plot, individuals of Vanellus vanellus L. and, to a lesser extent, Numenius arquata L. were present and defended their ranges against predators. A significantly lower frequency of predators over this study plot than the others was recorded, and the rate of predation (26 %) on the artificial nests in this plot was also significantly lower. The importance of this result for some current hypotheses about the role of predation in bird communities is pointed out.