Concentrations of plasma metabolites as predictors of nestling condition in the Great Cormorant (Phalacrocorax carbo sinensis)

Abstract

We investigated the reliability of basic plasma metabolite concentrations as predictors of body condition in the nestlings ofthe Great Cormorant (Phalacrocorax carbo sinensis) , a species with marked hatching asynchrony and well-established intra-brood hierarchies. For this purpose we analyzed relationships between the levels ofplasma proteins, triglycerides and glucose measured at the age of ca. 3 weeks with body mass, mass-size residuals, and growth rates of 185 Great Cormorant chicks from the colony in central Poland. Concentrations of all studied plasma metabolites correlated with at least one ofbody condition indices. We found concentration of plasma glucose to be the most robust predictor of body condition, as it was positively related with size-adjusted and unadjusted body mass, as well as with chick growth rates. The level of plasma proteins was found to be of limited practical applicability (positive relationship only with mass-tarsus residuals), while the usefulness of plasma triglycerides as an index ofbody condition was intermediate (positive relationships with mass-size residuals and growth rates). Predictive power of all significant relationships was low.