Distributions for key exposure factors controlling the uptake of xenobiotic chemicals by great blue herons (Ardea herodius) through ingestion of fish

A variety of exposure factors ultimately control the uptake of xenobiotic c hemicals by colonial piscivorous birds, such as herons and egrets. These fa ctors, which include feeding rate for various food sources, feeding territo ry size, and body weight, are critical to the implementation of models comm only used to predict ecological risks. A critical evaluation of literature on avian behavior, physiology, and ecology was conducted in order to identi fy those variables that most strongly influence uptake of chemicals by hero ns and egrets. After developing a database of such exposure factors, we ide ntified each factor's range, central tendency, and distribution. Sufficient information was available to allow the development of statistical distribu tions for body weight, fraction of diet from fish, prey length, distance to foraging site, and feeding territory size for great blue herons. The five distributions presented in this paper are intended to support probabilistic assessments of potential risks to great blue herons, Distributions of expo sure factors for great blue herons have not been previously published. With out such data, application of all but the most simple mechanistic models wi ll require point estimates, most of which will be overly conservative and w ill not support accurate characterization of actual exposures of herons at hazardous waste sites.