Vigilance and flocking behaviour of tactilely foraging Dunlins Calidris alpina

Desholm M., Wegeberg A. M. & Mouritsen K.N.


Field observations of the relationship between vigilance, foraging, and flocking behaviour in Dunlins Calidris alpina were carried out under optimal field conditions. The results show that central Dunlins within larger flocks devote less time to vigilant behaviour and more time to feeding (higher probing rate) than more peripheral conspecifics. The most coherent explanation for the difference in vigilance level between peripherally and centrally foraging Dunlins is the individual birds´ perception of a higher predation risk when exposed. It is argued that vigilance for predators in Dunlins constrains foraging activity rather than vice versa. Hence, the adaptive significance of flocking in Dunlins may be an increased feeding activity without jeopardising predator surveillance.