Northern Prairie Wildlife Research Center
Disturbances of canvasbacks (Aythya valisineria) by recreational boaters were studied on the upper Mississippi River to determine frequency of disturbance and possible energetic implications. Twenty-nine random observation periods during morning (30 min before sunrise to 1200 hr) and afternoon (1200 hr to sunset) were used to determine numbers by species, their dominant activity, and distribution on the staging area. Recreational boating activity that resulted in disturbance was recorded as well as flock size and duration of response. An average of 17.2 boats/day resulted in 5.2 disturbances/day. Sport fishermen accounted for 42% of the disturbances. Mean flock size of disturbed canvasbacks was 12,474 with 4.43 minutes/disturbance. Diving ducks were estimated to have left the staging area 19 times during the fall because of human disturbance. Birds may be forced to fly up to 1 hour each day due to disturbance. Energetic costs of the disturbances are unknown, but they may be detrimental if canvasback numbers significantly increase and require more food, American wildcelery (Vallisneria americana) winter bud production significantly decreases, disturbances become more severe, or foods at other migration areas deteriorate.