The capercaillie is Britain's largest grouse and is critically endangered in Scotland, with the remaining population of around 500 birds highly sensitive to human disturbance during breeding and in winter.
Capercaillie welfare at the individual and population level is intertwined. Disturbance at leks causes acute stress responses in displaying males and may cause females to leave without mating, directly reducing reproductive success. Fence collisions cause traumatic injury and death. Winter food shortages in degraded habitat cause gradual starvation in cold weather. At fewer than 500 individuals, every breeding failure and accidental death matters enormously to the long-term survival of the species. Visitor management that keeps people away from leks during February-May, combined with fence modification and habitat restoration, are the most directly welfare-relevant conservation interventions currently available.