The Significance of Body Mass to Female Dabbling Ducks during Late Incubation

• Published in: The Condor (Los Angeles, Calif.) Calif.), 1991-11, Vol.93 (4), p.811-816
• Main Authors: Gloutney, Mark L., Clark, Robert G.
• Format: Article
• Language: English
• Subjects: Anas; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Bird nesting; Breeding; Clutch size; Ducks; Eggs; Female animals; Freshwater; Fundamental and applied biological sciences. Psychology; Geese; Incubation; Nutrient reserves; Waterfowl
• ISSN: 0010-5422; 1938-5129
• DOI: 10.2307/3247715

Allocation of nutrients to eggs and to costs of incubation in waterfowl may be constrained by the need to maintain nutrient reserves to complete incubation. This hypothesis predicts that body mass of successfully nesting females is greater than that of unsuccessful females. This prediction was tested by comparing the body masses of successful and unsuccessful female dabbling ducks captured late in incubation. Successful Mallards (Anas platyrhynchos) and Northern Shovelers (A. clypeata) were significantly heavier than unsuccessful females, and this process constituted evidence of directional selection. Body masses of successful and unsuccessful Blue-winged Teal (A. discors) did not differ. We calculated residual (observed-predicted) body masses using published regression equations relating mass and stage of incubation in independent samples of shovelers and teal to test whether successful females in our study were relatively heavy. Residual body mass estimates of successful shovelers were significantly greater than those of unsuccessful ones; in teal, no relationship was found. Nutrient reserves may influence successful incubation in some prairie-nesting ducks and the relationship may be stronger in larger species that are most capable of storing nutrients.