Northern Prairie Wildlife Research Center
Disturbances of Eurasian wigeon by natural predators totaled 361, by man totaled 19, by planes totaled 19, and those for an unknown reason 58 (correspondingly as a percentage of the total disturbances: 82.7%, 3.4%, 3.4%, and 10.4%). Disturbances by man or plane generally affected a greater percentage of individuals at one time, 61.5% for man and 49.6% for planes. Time spent in flight per disturbance for predators varied from 8 sec to 58 sec while 34 sec was the duration of disturbance caused by man, and 9 sec by airplanes. Disturbances by man were chiefly by hunters, fishermen, planes, and especially helicopters at low altitude: these chiefly occurred during the day, and nocturnal disturbances were mostly caused by avian predators. Predators caused localized displacements, but those by man on a small body of water caused a total evacuation. If the disturbance occurred on a larger body of water, ducks regrouped in the middle. Ducks were very sensitive to fishermen who went into the water. Man's disturbances modified the periodicity of ducks' activities, and seriously affected feeding.