DAILY METABOLIZED ENERGY-CONSUMPTION OF OYSTERCATCHERS HAEMATOPUS-OSTRALEGUS FEEDING ON LARVAE OF THE CRANE-FLY TIPULA PALUDOSA

Oystercatchers feeding on grassland in spring mainly take leatherjacke ts, the larvae of the crane fly Tipula paludosa. The birds roost at ni ght and feed for 40 to 60% of the daylight period. Their intake rate d uring feeding is 1 to 1.5 mg AFDW or 20 to 30 J s(-1), which is rather low compared to the intake rates achieved on tidal flats. The digesti bility of leatherjackets was estimated in three ways: ash and chloroph yll were used as natural digestibility markers, and prey remnants in t he faeces were counted. On average, 86% of the ingested energy was ass imilated. The daily metabolizable energy consumption was estimated to be 640 kJ, which is equivalent to 2.6 x BMR. The costs of living were relatively low because the birds lived in thermoneutral conditions and flew for only about 15 min a day.