Tracing Nutrient Sources to Lipid Production in Birds and Insects Using Stable Isotope (δ13C, δ2H) Tracers: Implications for Nutritional Physiology of Migratory Species

Libesha Anparasan, The University of Western Ontario

Abstract

Using stable isotope measurements of inert tissues to determine origins and migratory patterns is well established. However, isotopically determining nutritional origins of lipids, the primary fuel of migration, has not been attempted. I explored isotopic links between diet and stored lipids in captive White-throated Sparrows (Zonotrichia albicollis) and true armyworm moths (Mythimna unipuncta) using δ¹³C and δ²H measurements. Isotopic discrimination between body lipids and diet was established as linear calibration functions. Isotopic uptake following a diet switch in moths was used to trace lipid accumulation over time. Isotopic correlations between breath metabolic by-products of fed and fasted sparrows were explored as indicators of lipid use. This study established isotopic (δ¹³C, δ²H) linkages between diet and stored lipids for migratory insects and passerines and advocates the use stable isotopes in lipids as a tool to evaluate nutrient origins and allocation strategies in a variety of migratory species.