Effects of group size and distance to protective cover on the vigilance behaviour of black-billed magpies pica pica

Abstract

We studied the influence of group size and distance to protective cover on scanning behaviour of Black-billed Magpies, considering their effects on scanning rate and scan duration. The percentage of time spent vigilant increased with increasing group size and with increasing distance to the nearest tree, but the way in which vigilance changed was different in both cases. Birds in larger groups scanned less, whereas birds near protective cover had shorter scans. © 1991 Taylor & Francis Group, LLC.