Diets of adult and nestling starlings (Sturnus vulgaris) in Hawke’s Bay,New Zealand

Abstract

Gizzards were examined from 334 adult and 62 nestling starlings collected in mixed farmland during 1971–72. The birds ate insects, spiders, earthworms, snails, millipedes, centipedes, seeds, and fruits. Starlings ate fewer subterranean animals (7%) than those usually living partially hidden (45%), on the ground (31%), or on vegetation (18%). About half the invertebrates eaten were 2–5 mm long and about a quarter 6–10 mm long. Nestlings tend to be fed significantly larger items than were eaten by adults. The commonest items in adult starlings were Coleoptera adults, Lepidoptera larvae, Hemiptera, and fruits; in nestlings, Coleoptera adults and Diptera adults and larvae were important. Earthworms were found in all the nestlings. More than 50% of adult gizzards contained earthworm chaetae in wetter months, but fewer in drier months. The diet of starlings, despite considerable overlap with the foods eaten by mynas, rooks, and magpies, included somewhat different components and proportions of the food supply. Fruits were found in adults only; most were probably eaten after harvest. Although predation on two major pasture pests—Costelytra zealandica and Wiseana cervinata larvae—was insubstantial, nearly 40% of the total invertebrates eaten by adult starlings were insect pest species.