Effects of DDT on birds at the Patuxent Wildlife Research Refuge

The spraying of DDT at the rate of 2 pounds per acre on a tract of land within the well-drained bottomland forest at the Patuxent Research Refuge on June 5, 1945, had little or no effect on the bird population of the area, with the possible exception of the redstart (Setophaga ruticilla). Considerable evidence was accumulated showing that this species was probably somewhat reduced. The effective dose for the treated area as a whole was decidedly less than 2 pounds of DDT per acre. Some spray was blown away to be deposited on nearby areas, and much of it was screened out by the dense forest canopy. The redstarts, being tree top feeders, were exposed to more DDT than most of the local birds.