Figure 4.

Response of crested pigeon flocks to playback of alarmed and non-alarmed wing whistles: (a) proportion of flocks fleeing; (b) mean time individuals spent vigilant among those that did not flee (with 95% confidence interval). Playbacks included alarmed and non-alarmed whistles at their natural amplitude, alarmed whistles at reduced amplitude to match non-alarmed whistles (alarm down), non-alarmed whistles at increased amplitude to match alarmed whistles (non-alarm up) and a control sound (parrot contact call, at alarmed amplitude). n = 15 matched playback sets for fleeing and 12 matched sets for vigilance because three flocks fled to the alarmed down treatment and so vigilance could not be measured. Vigilance data are unavailable for the alarmed playback because most flocks fled. n.a., not applicable.