WINTER FIELD USE BY THE EUROPEAN STARLING STURNUS-VULGARIS - HABITAT PREFERENCES AND THE AVAILABILITY OF PREY

A regular census of an Oxfordshire farm, U.K., showed that the resident Starlings Sturnus vulgaris preferred to feed in established pasture fields. Fields which were closer to the daytime roost, provided feeding areas further from hedges, and had shorter swards were particularly preferred. The Starlings' habitat preferences could also be explained in terms of the availability of prey. This was quantified via the foraging behaviour of individual birds allowed to forage in small enclosures in a sub-sample of the fields available to the flock. The experimental birds' prey capture rates in each of the fields were significantly correlated with the observed flock foraging densities. This was a prey-specific effect: although the birds could have obtained a higher energy intake rate by feeding on earthworms in less preferred fields, the Starlings were seen to feed in those fields which allowed them to maximise the amount of energy obtainable from leatherjackets. A laboratory prey choice experiment demonstrated that this field preference could be attributed to an absolute preference for leatherjackets over earthworms.