Physical distances among individuals in flocks of greater flamingoes (Phoenicopterus ruber) are affected by human disturbance

Use of flock members to reduce individual levels of vigilance has been the focus of many studies that have attempted to explain the relationship among vigilance, group size, and distance covered by using foraging or preening as indicators. To avoid the confounding variables associated with foraging and preening, the effects of increasing levels of disturbance on vigilance by measuring distances among individuals (D) in flocks of greater flamingoes was studied. During 61 h, reactions to 112 disturbances were recorded. Undisturbed flamingoes exhibited no relationship between D and flock size. When joggers appeared, birds became alert but continued to feed. D was uninfluenced by flock size when jeeps drove past, but was different in value from that in undisturbed flocks. However, when tours stopped and occupants got out of their vehicles, D was significantly reduced and flock size was positively correlated with flock cohesiveness, i.e., smaller flocks had smaller D values than larger flocks. Flamingoes were terrified of all-terrain vehicles, and in 82% of these encounters, they flew away. In these cases, flock cohesiveness was extremely dense, but flock size did not influence flock reaction. This study shows that flocking species seek protection in numbers, and they leave the area when insufficient conspecifics are present when serious disturbance occurs.