TIME AND ENERGY CONSTRAINTS ON COURTSHIP IN WINTERING AMERICAN BLACK DUCKS

Courtship in wintering American black ducks (A. rubripes) was studied at 3 sites that differed substantially in food supply. Courtship started earlier and occupied more of the duck''s time at the site where food was most nutritious. Ducks at the site with intermediate food quality only began courting after temperatures rose sufficiently to reduce their energetic costs of maintenance. Ducks with the least nutritious food began courting latest and spent the least amount of time in this activity. The seasonal sequence of courtship displays used by the courting ducks was similar between sites. Ducks with the best food (i.e., those starting courtship first) reached the peak of courtship activity earliest and thus should have been best prepared for breeding in the spring. The northern limit to winter ranges in species with early pairing may be determined, in part, by the availability of sufficient food for early courtship.