Changes in blood stable isotopes (δ13C, δ15N), plasma corticosterone and body mass in exercising birds using a wind tunnel

Abstract

Blood stable isotope compositions in birds reflect the dietary isotopic signature at the time of the cellular blood synthesis. Several studies suggest that stable isotope ratios of some elements such as nitrogen (δ15N) can change in response to individual metabolic and physiological conditions. Using a wind tunnel experiment we tested if endurance flight in birds alters the metabolic state and thereby induces changes in blood δ13C and δ15N values. We trained European starlings (Sturnus vulgaris), that were held under similar diet conditions, to fly in a wind tunnel for up to six hours. While there was a substantial post-flight increase in plasma corticosterone concentrations and a decrease in body weight, we found no significant difference in blood δ13C and δ15N values before and after flight. These findings suggest that blood δ13C and δ15N values from birds caught in the wild most likely reflect the dietary isotopic sources at