Midwest Fish & Wildlife Conference 2018

AUTHORS. Eric J. Smith, Western Illinois University; Christopher N. Jacques, Western Illinois University; Heath M. Hagy, US Fish & Wildlife Service; Michael J. Anteau, United States Geological Survey

ABSTRACT. The continental breeding population of lesser scaup (Aythya affinis) has declined markedly over the past 30–40 years.  Multiple factors have likely contributed to the long-term decline in the continental scaup population including reductions in recruitment, a decline in survival of female scaup relative to that of males, and decreases in forage quality and amount throughout the upper Midwest.  Decreases in aquatic vegetation and invertebrates have direct impacts on migrating lesser scaup and other wetland-obligate species.  Nutrient acquisition and storage during migration are important for survival and reproduction; specifically, lipids have been identified as an important nutrient for endurance flights and egg production.  Plasma-lipid metabolites (Triglyceride and ß-hydroxybutyrate) have been used for estimating rates of lipid accumulation or catabolism in wild birds which can be useful in assessing the relative quality of habitat during migration.  However, further development and refining of plasma-lipid metabolite indices (PLMIs) is needed to understand the effects of wetland degradation on migratory waterfowl.  Further, there is the potential for intersexual differences in metabolite concentrations for lesser scaup that may play a role in developing PLMIs and have yet to be explored.  We held wild lesser scaup in short-term captivity to develop an index for examining whether individuals are accumulating or catabolizing lipids by regressing known mass changes with plasma-lipid metabolite concentrations, and to have access to females which are more difficult to trap.  Triglyceride and ß-hydroxybutyrate predicted 53.8% of the variation in one-day mass changes for males (F=14.55, df = 2 and 25, P F=30.89, df = 2 and 27, P < 0.001).  Our analysis suggests that there are differences between sexes in triglyceride concentrations.  We will have the final analysis completed shortly and will provide this information during the presentation.