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 residen t Starlings Sturnus vulgaris preferred to feed in established pasture fields. Fields which were closer to the daytime roost, provided feedin g 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 fora ging behaviour of individual birds allowed to forage in small enclosur es in a sub-sample of the fields available to the flock. The experimen tal birds' prey capture rates in each of the fields were significantly correlated with the observed flock foraging densities. This was a pre y-specific effect: although the birds could have obtained a higher ene rgy intake rate by feeding on earthworms in less preferred fields, the Starlings were seen to feed in those fields which allowed them to max imise the amount of energy obtainable from leatherjackets. A laborator y prey choice experiment demonstrated that this field preference could be attributed to an absolute preference for leatherjackets over earth worms.