Abstracts

Presented by Kyla Bas - Email: kyla.bas@usask.ca

Determining how biotic and abiotic factors affect individual quality is important for understanding population processes and can help to inform management decisions. However, whether spring phenology and density dependence affect components of reproductive success in ducks is not adequately understood. Therefore, our objective was to test the effects of spring phenology and conspecific density on lesser scaup duckling quality. We evaluated the effects of local ambient air temperature during the breeding season and the effects of local brood density on body mass and body condition index of pre-fledging scaup ducklings captured (n=5330, ranging 120 - 1179 individuals captured per year) at Red Rocks Lake, Montana, 2010-2018. Mixed effects models incorporating random effects of year indicated that measurements of duckling quality may be related to pre-nesting temperature but were unrelated to ice-out date. Duckling mass was negatively associated with ambient air temperature during brood rearing, presumably due to adverse effects of cold weather on food and(or) growth. Duckling mass was also inversely related to duckling density, perhaps reflecting competition for food or high-quality habitat. Both these effects were more pronounced for younger ducklings. A scaled mass index was derived to describe duckling mass in relation to structural size and serve as a body condition index. The results for duckling body condition were comparable to those observed for duckling mass. Results were not consistent with the hypothesis that early spring phenology reduced duckling body quality; however, body mass was lower during years of higher duckling density.