SPATIAL AND TEMPORAL PATTERNS OF PREDATION OF SIMULATED SAGE GROUSE NESTS AT HIGH AND LOW NEST DENSITIES - AN EXPERIMENTAL-STUDY

We examined patterns of predation on 252 simulated sage grouse (Centro cercus urophasianus) nests placed at two densities around six active l eks in southeastern Wyoming, U.S.A. Predation intensity, as measured b y the frequency of multiple-nest predation events, was significantly g reater at high-density sites, implying enhanced prey capture (function al and (or) numerical response) by predators. Significant spatial aggr egation of nest predation further implies enhanced prey capture by pre dators at high prey densities. Predation varied significantly among si tes, but there were no significant first-order differences in predatio n between densities. Predation was also significantly affected by year -density and site-year-density interactions. Several factors, includin g nest cover, prey defense mechanisms, study site location, nest locat ion, year, search methods of predators, number of predators, and rando m encounter may inhibit or confound density-dependent nest predation. Enhanced prey capture provides a mechanism for density-dependent popul ation regulation.