The diet of DippersCinclus cincluswintering in the catchment of the River Wye, Wales

Abstract

We studied the diet of Dippers in the River Wye catchment by faecal analysis during the winters of 1983/84 and 1984/85. Diptera, Trichoptera, Ephemeroptera and Plecoptera comprised respectively 34, 23, 18 and 11% of 4650 items recorded from over 350 faecal samples. The Simuliidae (Diptera) and Baetidae (Ephemeroptera) were the commonest macroin vertebrate families recorded despite their small size. Fish and trichopteran larvae comprised respectively an estimated 63 and 19% of the diet by weight. By contrast with Dippers foraging for nestlings, the proportions and reconstructed weights of items appearing in faeces strongly reflected those in stream samples. Birds probably fed opportunistically. Consequently, Dippers feeding on hard water streams ingested more calcium-rich prey than those on soft-water streams. The results are discussed in relation to the influence of stream acidity on aspects of Dipper ecology.