Do topographical constraints and space availability influence birds’ ranging behaviour ? The Alpine Chough (Pyrrhocorax graculus) as a study case

Abstract

Summer home ranges and movements of Alpine Choughs Pyrrhocorax graculus radiotracked in a large Alpine top valley (Cervinia, Valtoumanche, northwestern Italian Alps) were compared with those radiotracked in a small Alpine top valley (Palanfrè, Val Grande, southwestern Italian Alps). Birds never flew beyond the mountain ridges delimiting the two areas. On average, home ranges at Cervinia were ten times as large as those at Palanfrè ; however, ratios between the extent of individual home ranges (MPC 100 %) and the area potentially available to birds were not significantly different in the two areas. Bird locations were rather scattered at Cervinia, whereas they were concentrated in a few cells at Palanfrè. The proportion of fixes spent at pastures and cliffs was lower at Cervinia than at Palanfrè. Finally, birds changed cells more often and flew for a longer distance at Cervinia than at Palanfrè. These results suggest that spatial structures of the landscape such as topographical constraints (high mountain ridges) and the extent of the area available to birds significantly affect movements and home ranges of the Alpine Chough. Movements also depend on mutual location of foraging and nesting sites and on typical ecological factors such as food availability and distribution. Therefore, we conclude that the summer ranging behaviour of the Alpine Chough is affected both by local topographical and ecological factors.