The energetic demands and welfare significance of black grouse lek display behaviour.
Black grouse lek behaviour represents one of the most energetically costly activities in British wildlife. Males arrive at lek sites in darkness, often after long flights from roosting areas. The display — involving bubbling calls, wing-drooping, tail-fanning, and jump-flights — continues for hours in all weather conditions. During peak lek season, males may display every day for weeks, sustaining enormous energetic costs.
The welfare implications of lek disruption are significant. Human disturbance — from walkers, photographers, or vehicles — causes lek abandonment. If females are present evaluating males, disturbance interrupts mate selection and may cause females to leave without mating, reducing reproductive success for the entire population. Repeated disturbance trains birds to abandon leks permanently, with lasting population consequences.
Predation at leks causes welfare harm beyond the individual death. The alarm behaviour triggered by a predator visit can disrupt the lek for hours. Goshawk attacks on black grouse at leks have been documented causing extended disruption well beyond the attack itself.