The effects of raven removal on sage grouse nest success
We measured the effects of common raven removal on the nest success of greater sage grouse. One cause of sage grouse population decline is thought to be reduced nest success due to egg depredation by ravens. Ravens are nest predators that have substantially increased in abundance in response to current human land-use practices. In many areas, wildlife managers use egg baits treated with DRC-1339 to reduce raven numbers in sage grouse habitat. The effects of raven removal on grouse nest success and identification of any compensatory nest predators are largely unknown. During 2002 and 2003, USDA WS removed ravens from an experimental area in Nevada, within which we deployed miniature, camouflaged video cameras with time-lapsed recorders at sage grouse nests. Using continuous video monitoring throughout the incubation period, we determined the identity and observed the behavior of sage grouse nest predators. Sage grouse nest success during 2002 and 2003 was 74% (n = 19), with no depredations of sage grouse nests or sage grouse nest visitations by ravens. We also observed the behavior of animals that encountered nests, and we identified possible biases with estimating raven “take” from the attrition of egg baits. We found video cameras to be effective devises for identifying predators. These results may be useful in formulating future predator removal activities for sage grouse management.