The Energetics of Prey Selection by Redshank, Tringa totanus (L.), in Relation to Prey Density

Abstract

The prey species mostly taken by the wading bird redshank, Tringa totanus (L.), on the shore belong to a number of taxa and include the amphipod crustacean Corophium volutator (Pallas), the decapod crustaceans Carcinus maenas (L.) and Crangon vulgaris (Fabricius), the gastropod mollusc Hydrobia ulvae (Pennant), the bivalve mollusc Macoma balthica (L.), and the polychaete worms Nereis diversicolor (O.F. Miller) and Nephthys hombergi (Lamarck) (Goss-Custard 1969; Prater 1970; Burton 1974; GossCustard & Jones 1976). The diet in a particular situation is affected by factors such as mud temperature and substrate which seem to affect the behaviour of the prey and thus their availability to the birds (Goss-Custard 1969, 1970a). This paper examines the influence of prey density on diet. The aims of the study were (1) to describe the diet at different prey densities, (2) to test whether the birds select between prey rather than simply take every available item they encounter and (3) if selection occurs, to test the hypothesis that the birds prefer the species which maximize the net rate at which they collect energy.