Wildlife Damage Management, Internet Center for
Date of this Version
September 1968
Abstract
Pest birds cause serious damage to agricultural crops in most situations only when the number of individuals is very high. Often, large populations of avian pest species spend the hours of darkness congregated in roosts where they become vulnerable to certain control methods. Such is the case in California where certain pest species, particularity starlings and blackbirds, can often be found roosting in cattail-tule marshes. From these relatively concentrated populations the birds disperse to cause in some, but not all, cases of serious damage to certain agricultural crops. The obvious disadvantage resulting from the tendency of these birds to concentrate in roosts is that the number of individuals often becomes extremely high and the resulting damage to local agricultural crops extensive. Conversely, the roost concentrations facilitate reduction of population size by application of an avicide on a roosting population. The major problem of reducing the numbers of bird pests occupying such roosts is centered in the selection of a suitable avicide, that is, an economically feasible compound which is as selective to the pest species as possible and which does not persist in, or contaminate the environment. Two likely candidate com-pounds for such use (based primarily on chemical characteristics which result in very low toxicity to mammals and some degree of avian selectivity) are 3-chloro p-toluidine hydrochloride (coded DRC-1339 by the Denver Research Center, U.S.D.I.) and the free base of this compound, 3-chloro, 4-methyl aniline (coded, I believe, DRC 1347). Both have been tested extensively in the Starling Control Research Laboratory at the University of California at Davis for use as avicides applied to cattail-tule roosts.