Courtship and Aggression in Canvasbacks: Influence of Sex and Pair-Bonding

Time-activity budgets, courtship, and aggression of paired and unpaired Canvasbacks (Aythya valisineria) were studied on the upper Mississippi River and on Long Point Bay, Lake Erie, during spring migration. Of Canvasbacks present, 25-28% were female of which 17-27% were paired. Paired Canvasbacks spent more time in foraging aggression and initiated and won more encounters than did unpaired individuals. Paired females engaged in more courtship-related threats, chases, and neck-stretches than did unpaired females. Paired females exceeded paired males in foraging aggression and in courtship behaviors such as neck-stretches and chases, with the trend in all chases reversing just before or upon arrival at nesting sites. Thus in the early stages of pairing, females rather than males appeared to assume the primary role in foraging aggression and repelling courtship advances of other males.