Responses of Wild Pheasants to Solid-Block Applications of Aldrin

Abstract

The responses of wild pheasants (Phasianus colchicus) to single, aerial applications of 2 lb technical aldrin (granular form) per acre on a 12,450and a 29,880-acre block of farmland in eastern Illinois in April of 1960 and 1961, respectively, were divided into three major stages. First, the mortality of adult pheasants within a month of aldrin application was from 25 to 50 percent. Second, reproduction by surviving pheasants was severely depressed in the year of aldrin application as evidenced by the meager abundance of chicks and the abnormally high proportion (52-56 percent) of broodless hens in summer, the low ratio (relative to the untreated study area) of young per adult hen in autumn, and reduced numbers of cock-calls the following spring. Third, satisfactory reproduction occurred on the treated areas during the breeding season following the year of aldrin application. Adequate recovery of pheasant populations in farmland habitat can be expected within 2-3 years after single, solidblock applications of 2 lb aldrin per acre if (1) the areas treated are not so large as to prevent adequate repopulation by ingress from adjacent, untreated habitat, and (2) the pheasants on the adjacent, untreated land area maintain their population levels. The toxic effects of many chemical pesticides on wildlife species have been well documented, particularly in laboratory studies. Less emphasis has been placed on determining the ability of wild populations of animals to regain the losses suffered from applications of pesticides to their habitats. In 1960 and 1961, aldrin, one of the chlorinated hydrocarbons, was applied by the Illinois Department of Agriculture in cooperation with the Plant Pest Control Branch of the U. S. Department of Agriculture on selected areas of agricultural land in Iroquois County, Illinois, to suppress or contain infestations of Japanese beetles (Popillia japonica). This paper reports the effects of single, solid-block applications of 2 lb aldrin per acre on pheasant populations during the year of treatment, and documents the recovery of these pheasant populations during posttreatment