Large-Scale Evaluation of Blackbird Frightening Agent 4-Aminopyridine in Corn

Abstract

Cracked corn treated with 4-aminopyridine was effective in reducing damage to field corn by blackbirds (primarily red-winged blackbirds [Agelaius phoeniceus]) in Ohio. Damage measured in treated fields (0.8 percent) was significantly (P < 0.01) less than damage in untreated fields (3.4 percent) in the same area. The cost-benefit ratio was $0.72/ha. Only 14 nontarget birds (all house sparrows [Passer domesticus]) were found affected. J. WILDL. MANAGE. 40(1):126-131 The bird-frightening chemical 4-aminopyridine (Avitrol@, Avitrol Inc., Tulsa, Oklahoma; reference to commercial products does not imply endorsement by the U.S. Government), hereafter referred to as 4-AP, has gained widespread application in protecting maturing field corn from blackbird attack. Goodhue and Baumgartner (1965) first described the repellent effect of 4-AP wherein birds consuming treated grain exhibit distress symptoms before dying that prompt other flock members to leave the area. They reported that house sparrows, pigeons (Columbidae), brownheaded cowbirds (Molothrus ater), redwinged blackbirds, and starlings (Sturnus vulgaris) were repelled from local feeding areas when individuals of these species ingested 4-AP-treated grain or treated grain incorporated into bait mixtures. In a small-area test in Ohio, using treated and control fields, Stickley et al. (1972) showed the efficacy of 4-AP in protecting individual cornfields from blackbirds for a 6-day period following 1 application of #6-sized cracked corn bait (1 particle treated with 3 percent 4-AP for every 99 untreated particles) applied by hand to the ground at the rate of 4.5 to 5.6 kg/ha. In large-area tests, personnel of the Denver Wildlife Research Center demonstrated effectiveness of 4-AP in reducing blackbird amage to field corn over a 244-km2 area in South Dakota, first as a solution applied to husked ears on the stalk (De Grazio et al. 1971) and then on #6 cracked-corn bait (dilution ratio of 1:29) spread on the ground by hand as soon as fresh damage was noted (De Grazio et al. 1972). Fields were baited from one to seven times in this latter test. In these large-scale studies, proof of efficacy was based on prior-year damage and bird population levels; concurrent control areas were not used. This paper describes a large-scale test of efficacy of a product formulation of 4-AP that is roughly equivalent to the product Avitrol FC Corn Chops-99 registered by the U.S. Environmental Protection Agency in 1972 for use in field corn. The importance 1Present address: Natural Resource Ecology Laboratory, College of Natural Sciences, Colorado State University, Fort Collins 80523. 126 J. Wildl. Manage. 40 (1):1976 This content downloaded from 207.46.13.126 on Sat, 24 Sep 2016 04:50:05 UTC All use subject to http://about.jstor.org/terms EVALUATION OF 4-AP IN CORN Stickley et al. 127