The aquatic warbler is Europe's rarest migratory passerine bird, using UK wetlands during autumn passage on its way to West African wintering grounds.
Aquatic warblers passing through UK wetlands depend on productive, wet, lightly managed sedge marshes for feeding and fattening before crossing the Sahara. Overly intensive grazing, drainage, and scrub encroachment all reduce habitat suitability. Given the species' perilous global status, welfare of individual birds during UK passage carries population-level significance. Protecting and restoring key passage wetlands is a direct welfare and conservation intervention.