Shell Thinning in Eggs of Ungava Peregrines

Abstract

Breeding populations of the Peregrine Falcon (Falco peregrinus) disappeared from many areas of North America during the period between 1950 and the early sixties (Hickey, 1969) but Peregrines have continued to persist in apparently normal numbers in northern Canada and in Alaska (Enderson and Berger, 1968; Enderson et al., 1968;Cade et al., 1968).In Britain, California, and the eastern United States Peregrine eggs collected during the period of the decline were subsequently found to be thin-shelled (Ratcliffe, 1967;Hickey and Anderson, 1968).In this paper we report on shell thinning observed in Peregrine eggs obtained from the Ungava region of northern Quebec and adjacent islands of the Northwest Territories in 1967 and 1970.