Waterfowl often fail to use foods that seem plentiful to the investigator. The extent to which selective feeding or rejection of foods is a function of behavioral and morphological adaptations of the species, conditioned behavior of the individual, or individual preference for certain foods has not been appraised. The objectives of our study were to determine: (1) the extent of selective feeding among juvenile Canvasbacks (Aytha valisineria) and redheads (A. americana), (2) which food items were and which were not utilized, and (3) how selective use was related to the relative quality and availability of the food resource. In another paper (Bartonek and Hickey, MS) we present findings on the food habits of juvenile and adult Canvasbacks, Redheads, and Lesser Scaup (Aytha affinis) in southwestern Manitoba primarily during late spring and summer.
Only a few of the limited number of investigations into the summer food habits of waterfowl correlate use of foods with the relative quantity and/or availability of potential foods (White, 1936; Beard, 1953; Keith, 1961; Chura, 1961; Perret, 1962; Collias and Collias, 1963). Perret (1962) concluded that seasonal variations in the food habits of Mallards (Anas platyrhynchos) were related to changes in the availability of foods.
