Diet of Canvasbacks During Breeding

Introduction

Knowledge of foods consumed by ducks relative to stage of reproduction has aided our understanding of their nutrient requirements and habitat preferences during breeding (Krapu and Reinecke, in press). High energy foods are valuable to prelaying females (Krapu 1974, Hohman 1985, Noyes and Jarvis 1985) to increase fat reserves used during egg production and incubation (Drobney and Frederickson 1979, Barzen and Serie 1990). During egg-laying, females rely on foods high in protein, such as aquatic invertebrates, to supply the protein necessary for egg production (Krapu and Reinecke, in press).

Bartonek and Hickey (1969) reported that the proportion of animal foods consumed by canvasbacks was greatest during breeding, but they did not differentiate results by stage of reproduction. On Ruby Lake, Nevada, the proportion of animal foods in female canvasbacks differed among reproductive periods (Noyes and Jarvis 1985). However, their intermountain study area is at the periphery of the canvasback's breeding range and may not be representative of breeding habitat for the species (Bellrose 1980). The majority of canvasbacks breed in the parklands and mixed-grass prairie of Canada and the Dakotas, with highest breeding densities in the aspen parklands of southwestern Manitoba near Minnedosa (Bellrose 1980, Stoudt 1982). We describe the diet of breeding canvasbacks in southwestern Manitoba relative to their stage of reproduction.

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