De. Chamberlain et al., Importance of feeding ecology to the reproductive success of Blackbirds Turdus merula nesting in rural habitats, IBIS, 141(3), 1999, pp. 415-427
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.