The diet of breeding Dippers Cinclus cinclus and their nestlings in the catchment of the River Wye, mid-Wales: a preliminary study by faecal analysis

A preliminary study by faecal analysis into the diet of seven pairs of breeding Dippers and their nestlings was undertaken in the catchment of the River Wye in spring 1983. Macro-invertebrate items in faeces could be identified to family and quantified on the basis of mouthparts whilst the macro-invertebrate prey available to each pair of Dippers was assessed quantitatively by riffle-sampling.
In terms of numerical abundance, ephemeropteran nymphs, particularly Baetidae, and trichopteran larvae, particularly Hydropsychidae, were more important to adults and nestlings, respectively. When prey weights were taken into account, trichopteran larvae were the most important macro-invertebrate group to both, but especially to nestlings.
Some macro-invertebrate groups were selected in proportion to their abundance in the environment although indices of electivity indicated that prey selection for adults and nestlings, respectively, was negatively and positively correlated with prey weight. Significant changes in diet were also apparent with nestling age: smaller items, such as ephemeropteran nymphs, were eaten by younger nestlings whilst larger items, such as trichopteran larvae, became more frequent up to Day 15 after hatching.