The distribution of breeding dippers (Cinclus cinclus (L.); Aves) in relation to stream acidity in upland Wales

SUMMARY. 1. The distribution of breeding dippers was assessed in 1984 over seventy‐four sites on soft‐water streams throughout mid and north Wales. 2. Sites without breeding dippers had significantly higher mean concentrations of filterable aluminium, lower mean pH, fewer trichopteran larvae and ephemeropteran nymphs, and were on rivers with more conifer afforestation on their catchments, than sites where dippers were present. 3. We speculate that influences which increase the acidity of soft‐water streams could be detrimental to their populations of dippers, although further data are required on causative mechanisms.