Effects of Nest-Site Selection on Depredation of Artificial Nests

Abstract

We compared depredation of artificial arboreal nests between nests placed at nest sites used by birds in the previous season (actual nests) and those located at random nest sites (random nests) on a ruffed grouse (Bonasa umbellus) management area in central Pennsylvania from May to July 1987. Ninety-eight (65%) actual nests and 109 (73%) random nests were disturbed by predators. The number of actual and random nests disturbed did not differ (P = 0.74) from expected. Fate (undisturbed vs. disturbed by predators) of actual and random nests was not related (P > 0.05) to time of nest placement during the study or to plot age, nest height, nesting substrate, and woody stem densities at ground level or at nest height. Because nesting substrate and, hence, degree of nest conspicuousness varies among bird species in nature, we suggest that results obtained from studies of predation on artificial nests be used with caution. J. WILDL. MANAGE. 53(1):21-25 Depredation of artificial avian nests may vary with time of placement, age of plot, height of nests above ground, extent of forest fragmentation, and degree of concealment provided by vegetation surrounding nest sites (Sugden and Beyersbergen 1986, Yahner and Cypher 1987, Yahner and Scott 1988). In artificial nest studies, nests typically are placed at random nest sites selected by the investigator, e.g., in the nearest tree or shrub species (Yahner and Scott 1988). However, whether or not depredation of artificial nests placed at random nest sites differs from that of artificial nests placed at nest sites selected by birds is unknown. If artificial nests at these 2 types of nest sites differ in susceptibility to predation, then caution would be advis d when interpreting results obtained from artificial nests placed at random and extrapolati g to depredation of avian nests in nature. Our objectives were to compare depredation rates between artificial nests placed at random ne t sites to those placed at nest sites used by birds in the preceding breeding season, and determine if depredation of nests at these 2 types of nest sites is related to time of nest placement uring the breeding season or to plot age, nest height, nesting substrate, and woody stem densiti at ground level or at nest height. We thank J. L. Bauer for field assistance and T. E. Morrell for reviewing the manuscript. Funding for this research was provided by the I Present address: Box 175, Spangler, PA 15775. This content downloaded from 207.46.13.33 on Sat, 26 Nov 2016 04:10:49 UTC All use subject to http://about.jstor.org/terms 22 DEPREDATION ON ARTIFICIAL NESTS * Yahner and Voytko J. Wildl. Manage. 53(1):1989 Pennsylvania Agricultural Experiment Station and the Max McGraw Wildlife Foundation. This is Journal Series Paper 7826 of the Agricultural Experiment Station, The Pennsylvania State University, University Park.