Individual distances among Greater Flamingos as indicators of tourism pressure

One of the greatest challenges facing ecologists and conservationists is to ensure the continued co-existence of wildlife with the increasing pressure of human recreation. In birds, the use of flock members to reduce individual levels of vigilance has been the focus of many studies that have tried to explain the relationship among vigilance, group size, and distance to cover by using foraging or preening as indicators of disturbance. To avoid the confounding variables associated with foraging and preening, in this study I observed the effects of increasing levels of human disturbance on vigilance by measuring distances among individuals in flocks of Greater Flamingos (Phoenicopterus ruber roseus). Reactions to 112 disturbances were recorded during 61 hr of observation. Undisturbed flamingos exhibited no relationship between individual distance and flock size. When joggers appeared, birds became alert but continued to feed. Individual distance was not influenced by flock size when motor vehicles (jeeps) drove past, but was different in value from that in undisturbed flocks. However, when tour groups stopped and the occupants got out of vehicles, individual distance was significantly reduced and flock size positively influenced flock cohesiveness (i.e., smaller flocks had smaller individual distance values than large flocks). Flamingos appeared to be especially disturbed by all-terrain vehicles (ATVs), and in 82% of the encounters they flew away. In these cases, flock cohesiveness was extremely dense, but flock size did not influence flock reaction. This study demonstrated that flocking species seek protection in numbers, but they leave an area when insufficient conspecifics are present and when serious disturbance occurs.