Dippers are uniquely adapted British birds that walk underwater to forage on aquatic invertebrates. Their welfare is a sensitive indicator of upland river health and acidification.
Dippers in acidified or invertebrate-poor rivers experience nutritional stress that reduces breeding success and adult survival. The requirement for abundant aquatic macroinvertebrates means that river catchments with poor water quality directly impair dipper foraging. Adults in territories with low invertebrate abundance spend more time foraging and less time in other activities including territory defence, pair bond maintenance and nest watching. Chick provisioning in poor-quality rivers requires adults to forage for longer to provide adequate food, increasing adult energy expenditure. The welfare of individual dippers is therefore a direct function of the ecological quality of their river territory.