Population declines of the magpie Pica pica in Huntingdonshire and other parts of eastern England

Abstract

Since the second world war, the magpie Pica pica is known to have suffered population declines in parts of eastern England. To understand more fully the reasons for these declines, the status and fate of the magpie population in the County of Huntingdonshire (now part of Cambridgeshire) have been examined in detail. Some decline occurred prior to the mid 1950s, associated with changes in habitat. During the late 1950s and early 1960s, the breeding population decreased markedley to perhaps about 5% of its pre-war level. Mortality caused by dieldrin and other cyclodiene insecticides was the most likely single cause of this sudden decline. The population remained at a low level until about 1974. Since then there has been some recovery although the magpie is still relatively rare. Failure to recover more rapidly may be linked with the sedentary nature of this species precluding any significant recovery via immigration.