Abstract

Capsule Vegetation structure and invertebrate abundance interact to influence both foraging sites and
nestling provisioning rate; when invertebrate availability is low, adults may take greater risks to provide
food for their young.
Aims To investigate nesting and foraging ecology in a declining farmland bird whose fledging success
is influenced by the availability of invertebrate prey suitable for feeding to offspring, and where perceived
predation risk during foraging can be mediated by vegetation structure.
Methods Provisioning rates of adult Yellowhammers feeding nestlings were measured at nests on arable
farmland. Foraging sites were compared with control sites of both the same and different microhabitats;
provisioning rate was related to habitat features of foraging-sites.
Results Foraging sites had low vegetation density, probably enhancing detection of predators, or high
invertebrate abundance at high vegetation density. Parental provisioning rate decreased with increasing
vegetation cover at foraging sites with high invertebrate abundance; conversely, where invertebrate
abundance was low, provisioning rate increased with increasing vegetation cover.
Conclusions Vegetation structure at foraging sites suggests that a trade-off between predator detection
and prey availability influences foraging site selection in Yellowhammers. Associations between parental
provisioning rate and vegetation variables suggest that where invertebrate abundance is high birds
increase time spent scanning for predators at higher vegetation densities; however, when prey are scarce,
adults may take more risks to provide food for their young.