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Abstract
The effect of Plagiorhynchus cylindraceus (Acanthocephala) infection in the European starling (Sturnus vulgaris) was assessed by comparing the acquisition and use of energy by infected and uninfected adult starlings under stressed (4$\sp\circ$C) and unstressed (25$\sp\circ$C) conditions. Two infected females died during acclimation to stressed conditions. Infected male and female starlings, whether stressed or not, exhibited lowered standard metabolic rates (SMR) due to reductions in energy expended in basal metabolism and/or thermal regulation. Whether stressed or not, infected males ingested more energy per gram body weight while maintaining the same levels of metabolizable energy (ME) as uninfected males. Unchanged ME levels resulted in significantly greater energy being available for all body functions in infected males on a weight specific basis. In conjunction with a decreased SMR and the maintenance of a lower average daily body weight by stressed infected males, increased ME dictated that proportionately more energy was expended by infected birds for digestion, waste and excrement formation, and activity. These results indicate that infected birds were less able to maintain normal body temperature when stressed, possibly as the result of a lowered basal metabolism, and that infected birds have reduced digestive abilities requiring the ingestion of more food to meet energy demands.
