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Population trends
The dipper population throughout Europe is relatively stable, though regional declines and even local extinctions are reported.
Dippers have declined in west Wales, south-west and north-east England and various parts of Scotland since 1970, while the population has remained stable elsewhere. Acidification of streams, caused mainly by airborne pollutants creating acid rain, in these parts of the country appears to be the primary reason for this. Coniferous trees close to streams and in catchment areas can exacerbate this, since they trap acidic pollutants on their foliage, and consequently have more acidic water draining from them. The acidification reduces the abundance of aquatic invertebrate prey and may also cause calcium deficiency in egg-laying females resulting in thinning of eggshells.
In central Europe declines in dipper numbers arise as a direct result of industrial pollution, while hydroelectric and irrigation schemes that reduce flow rates in otherwise suitable watercourses are the most likely reasons for decline in the southern Europe.