The black tern has declined dramatically in the UK and Europe due to loss of shallow, productive wetlands essential for breeding and foraging.
Black terns that attempt to breed in degraded or drained wetlands face poor reproductive success — nests placed on floating vegetation are vulnerable to wave action and water level changes. Food availability is tied to insect abundance over productive shallow wetlands, which has declined sharply with agricultural intensification. Welfare of remaining breeding attempts is poor where habitat is suboptimal.