The food of breeding Marsh HarriersCircus aeruginosusin East Anglia

Abstract

In East Anglia in 1983–84, Marsh Harriers preyed upon most species of birds and mammals present in their hunting areas. Small birds, young gamebirds and waterbirds and mammals formed 90-95% of the diet by numbers and weight. Small adult birds and mammals were important in April-May, but thereafter young gamebirds and waterbirds formed an increasing proportion of the diet, whilst the proportion of mammals declined. Females and polygynous males took larger prey after the young had hatched than did monogynous males. There was no difference in the proportions of large prey taken by polygynous males and the much larger females. There was some evidence of a difference in diet for monogynous males, in the latter part of the season, when they took fewer mammals and more small birds. Polygynous males took larger prey later in the season, mainly by taking larger individuals of the same species. There was no evidence that the proportion of large prey brought by males to individual nests was linked to brood size.