Effect of Diflubenzuron Application on Eastern Deciduous Forest Birds

Abstract

We conducted a replicated experiment in eastern West Virginia to examine the effect of diflubenzuron on the abundance of deciduous forest birds. Diets of 7 insectivorous bird species and foraging behavior of male red-eyed vireos (Vireo olivaceus) also were examined in treated and untreated areas. Although caterpillars were less common on treated areas, none of the 21 common bird species was significantly (P < 0.10) more abundant in untreated than treated plots. Significant differences in the percentage of Lepidoptera larvae in diets were observed for all species examined except the worm-eating warbler (Helmitheros vermivorus) and blue-gray gnatcatcher (Polioptila caerulea). Two different measures of area covered per unit time spent foraging indicated that vireo foraging areas were 3.1 and 2 times larger on treated areas than on untreated areas, respectively. Differences in diet and foraging behavior were likely related to the decrease in abundance of caterpillars on treated plots. J. WILDL. MANAGE. 54(3):486-493 Since its introduction into the northeastern United States in 1869, the gypsy moth (Lymantria dispar) has become an important insect pest of eastern deciduous forests because of its rapid population growth, its ability to thrive on a variety of host plants, and its lack of natural predators. Various methods have been used to control gypsy moth populations, including introduction of parasitoids and microbial diseases, management of predator populations, sterile male introductions, and pesticide applications (Doane and McManus 1981). Pesticides have been most effective in reducing gypsy moth populations, but are in disfavor because of possible harmful environmental effects. Also, use of broad spectrum pesticides may preclude effective use of many of the above control measures (U.S. For. Serv. [USFS] 1985). The insect growth regulator diflubenzuron (1' Present address: Department of Wildlife, Humboldt State University, Arcata, CA 95521. 2 Present address: Garrett Community College, McHenry, MD 21541. 3 Present address: Chemical and Agricultural Products Division, Abbott Laboratories, 14th and Sheridan, North Chicago, IL 60064. 4 Present address: Clement Associates Inc., 9300 Lee Highway, Fairfax, VA 22030. This content downloaded from 157.55.39.55 on Sun, 12 Jun 2016 06:04:41 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 54(3):1990 DIFLUBENZURON EFFECTS ON BIRDS * Cooper et al. 487 Table 1. Mean densities (N/40 ha) of common bird speciesa in areas treated with diflubenzuron and untreated areas of Sleepy Creek Public Hunting and Fishing Area, West Virginia, 1985-86.