The marsh harrier (Circus aeruginosus) has made a remarkable recovery from near-extinction in Britain to a widespread breeding species in wetland habitats. Its conservation story illustrates how habitat restoration and protection can reverse precipitous decline.
By the 1970s, marsh harrier breeding in Britain had been reduced to a single pair at Minsmere, Suffolk—one of the most precarious positions of any British bird of prey. Persecution, habitat drainage, and organochlorine pesticide accumulation caused this catastrophic decline. Protection, wetland restoration, and the pesticide ban enabled population recovery: by the 2020s, over 400 breeding females are recorded annually across Britain.
Marsh harriers are closely associated with extensive reedbeds, wetland margins, and wet grasslands for nesting and hunting. They build nests in dense emergent vegetation, typically phragmites reeds, and hunt over open water, reedbed edges, and wet grassland. The recovery of marsh harriers has closely paralleled the conservation expansion of reedbed habitat through agri-environment schemes and wetland creation projects.
Marsh harriers are opportunistic predators hunting with characteristic low quartering flight over reeds and grassland. Prey includes waterfowl (ducklings and chicks), small mammals, frogs, and invertebrates. They are one of the few raptors able to take prey on water surfaces. This hunting flexibility enables them to exploit diverse wetland habitats and adapt to seasonal prey availability changes.
Despite recovery, marsh harriers face ongoing threats: illegal persecution on some estates; accidental persecution through secondary rodenticide poisoning; lead shot accumulation from scavenged wildfowl; and habitat deterioration through wetland drainage, reduced water table management, and reedbed succession. Climate variability affecting water levels can affect nesting success in shallow-flooded reedbeds.
Reedbed creation and management under agri-environment schemes and through NGO reserve management has been critical to marsh harrier recovery. Maintaining water table levels in reedbeds through ditch management and sluice control provides optimal nesting conditions. Strategic wetland creation at landscape scale creates connectivity between isolated wetland fragments. RSPB, Wildlife Trusts, and Natural England partnerships have driven the wetland creation agenda that incidentally benefits marsh harriers.