Impacts of ski-development on ptarmigan (Lagopus mutus) at Cairn Gorm, Scotland

This paper reports adverse impacts on numbers and breeding success of ptarmigan (Lagopus mutus) in 1967-1996 at a ski area in the Cairngorms massif, where ptarmigan normally show 10-year population cycles. An influx of carrion crows (Corvus corone), generalist predators, followed the development. On the most developed area near the main car park, ptarmigan occurred at high density but then lost nests to frequent crows, reared abnormally few broods, died flying into ski-lift wires and declined until none bred for many summers. On a nearby higher area with fewer wires, ptarmigan lost nests to frequent crows and reared abnormally few broods, but seldom died on wires. Adult numbers declined and then became unusually steady for over two decades, with no significant cycle. On a third area further from the car park, ptarmigan lost fewer nests to the less frequent crows but bred more poorly than in the massif’s centre, and showed cycles of lower amplitude than there. On a fourth area yet further away, with few or no crows, ptarmigan bred as well as in the massif’s centre and showed cycles of the same amplitude as there.