Effect on Forest Birds of DDT Used for Gypsy Moth Control in Pennsylvania

Abstract

Between April 18 and June 28, 1945, the birds populations on three tracts near Scranton, Lackawanna County, Pennsylvania were determined by repeated, systematic census trips. One tract (Mile Square) comprised about 40 acres adjacent to a 1-mile trail in Spring Brook Valley, 6 miles south of Scranton. The trail extends from one edge to beyond the center of a forested area of about 600 acres that in late May and early June was sprayed by airplane with 5 pounds of DDT per acre for experimental control of gypsy moth larvae and to determine the effect of DDT upon other insects. This dosage is several times that needed for control of the gypsy moth and is the maximum considered necessary by entomologists for any forest insect pest. The second tract (Maple Lake), 6 miles southeast of Scranton and one mile west of Maple Lake, comprised 40 acres in an area of about 350 acres of rolling land mostly forested. The area was sprayed by airplane on June 9 with 1 pound of DDT per acre for experimental control of gypsy moth larvae and to determine the effect of this concentration on other insects. The third tract (Check), 6 miles southeast of Scranton and a mile northwest of Maple Lake, was a 40-acre portion of an extensive untreated forest