Importance of feeding ecology to the reproductive success of Blackbirds Turdus merula nesting in rural habitats

The feeding ecology of Blackbirds Turdus merula breeding in contiguous wood land and farmland habitats was studied over three years. The aim of the stu dy was to investigate how reproductive success was influenced by nestling d iet and the provisioning rates of parents feeding nestlings. Parental provi sioning rates increased with brood size, and consequently individual nestli ngs were no lighter in larger broods. None of the environmental factors mea sured had strong effects on parental provisioning rate. The nestling diet w as dominated by caterpillars and earthworms, the former occurring in a shor t period in the middle of the breeding season. The availability of earthwor ms was higher in woodland and was dependent on rainfall in farmland. Nestli ng mass and provisioning rates were marginally higher under predominantly e arthworm diets. Nestling mass increased with rainfall in farmland only, and was higher in farmland than in woodland or woodland-edge, although it is d oubtful whether this result is of any significance for fledgling survival. Overall, Blackbirds were able to provision their nestlings adequately throu ghout the breeding season across a range of conditions. There was no eviden ce to suggest that reproductive success was constrained by aspects of feedi ng ecology within the natural range of brood size.