DRC-1339 Egg Baits: Preliminary Evaluation of Their Effectiveness in Removing Ravens

Author(s): Coates, Peter S. | Abstract: I measured the preliminary effects of chicken egg baits treated with DRC-1339 on removing common ravens for the purpose of reducing raven depredation of prairie grouse nests in northeastern Nevada. Greater sage grouse and Columbian sharp-tailed grouse are game species that are declining in distribution and abundance throughout their historic range. Reduced nest success due to egg depredation by ravens is thought to be an important cause of nest failure. Ravens are subsidized nest predators that have substantially increased in abundance throughout their range within the past 25 years. During 2002-2004, I removed ravens from a treatment site using chicken egg baits treated with DRC-1339 to protect sage grouse and a nascent population of reintroduced Columbian sharp-tailed grouse in northeastern Nevada. I performed raven surveys at the treatment site and 2 control sites, located 22 and 53 km northwest of the treatment site, to measure the effects of using DRC-1339. Preliminary analyses indicate chicken egg baits treated with DRC-1339 significantly reduced raven densities at the treatment site, and change in densities over time was different at the treatment site than the control sites (F = 10.212,59, P l 0.001). Also, anthropogenic resource subsidies (i.e., power-lines, roads, agricultural fields, and public landfills) appeared to influence raven abundance. If lethal removal of ravens is implemented as a short-term management action to protect areas from ecological or economical damage, the technique described here is valuable to managers.