DRC-1339 use and control of common ravens

Abstract

Author(s): Spencer, Jack O., Jr. | Abstract: The U.S. Fish and Wildlife Service (USFWS) and the Nevada Division of Wildlife (NDOW) have both observed an increase in the population of common ravens (Corvus corax) throughout Nevada. This increase is suspected to be the result of, at least in part, supplemental feeding sources (landfills, road kills, feedlots, etc.). The increase is of concern to wildlife managers because ravens are known nest predators, and in excessive numbers they could adversely affect a wide variety of game birds, including the sage grouse (Centrocercus urophasianus). During the spring in both 2000 and 2001, Wildlife Services (WS) was contracted to manage raven numbers in a critical sage grouse nesting area in northern Washoe County. The primary management tool used by WS was the registered avicide DRC-1339, because it can be selectively used on birds that feed on eggs. A prepared DRC-1339 solution was injected into hard-boiled chicken eggs and placed in artificial nest sites located throughout the project sites. Ravens foraging in the nesting area for sage grouse eggs found and consumed the treated eggs and died, thus selectively removing the nest-raiding birds from the immediate area of the grouse nesting sites. No long-term effect is anticipated on the raven population, because treated eggs were placed out only in the immediate area of the nesting grouse and only during the brief nesting period. The possibility of secondary poisoning resulting from DRC-1339 use is considered unlikely because the active ingredient, 3-chloro-p-toluidine hydrochloride, is broken down into a non-toxic substance and expelled prior to the bird expiring. Consumption of DRC-1339 results in death due to renal failure in avian species. Ravens found after treatment were monitored for the presence of West Nile virus titers.