Winter movements of the Alpine chough: implications for management in the Alps

Abstract

The home ranges and movements of marked Alpine choughs (Pyrrhocorax graculus) were investigated in Aosta Valley, western Italian Alps, in two study sessions: winter-spring 1996-1997 and winter-spring 1997-1998. Overall 28 birds were marked, six of these were also equipped with a small radio tag. Home range sizes of 17 birds were estimated with the minimum convex polygon method (MCP), harmonic mean analysis (HC) and Kernel analysis. Alpine choughs resulted to be highly gregarious: home ranges of marked birds in fact overlapped throughout winter and spring. Feeding areas location and home range sizes varied dramatically from October to May in both study sessions. Climatic factors, food availability and food quality probably influenced the spatial distribution of this species. Before the snowfalls, birds remained above the tree line, frequently using food provided by tourists at refuges and picnic areas. After the first snowfall in November most feeding took place in shrubbery at 1500 m. When the amount of snow cover became too deep the Alpine choughs came down to the valley bottoms and its surroundings (600-1000 m) to forage in apple-orchards by day and flew back up into the mountains to roost. In March and April these birds frequented villages at valley tops (visiting picnic areas or foraging in snow-free patches). In late spring, they went back to the higher grounds on the valley tops. The importance of tourist development and of traditional agricultural practices for Alpine chough winter survival is discussed.