An application of stable isotope ecology to the study of raptor diets

Stable isotope analysis is an important tool used by geologists and geochemists. During the last two decades, ecologists have found the predictive characteristics of stable isotope variation useful in the study of biological systems. Isotope analysis can be used to study aspects of the natural history of birds such as diet and migration patterns. Bioaccumulation of heavy nitrogen is the key to studying the diet of raptor species from multiple ecoregions. Feather tissue is a non-destructive and relatively easy tissue to collect and analyze. Significant differences in isotope ratios were not detectable among samples from multiple locations in single large feathers. Stable isotope analysis shows that within a species, prey selection can be highly variable with many individuals appearing to select prey from different trophic levels. The diets of Broad-winged Hawks were found to be eating at a lower trophic level in Alberta than what the literature would predict. Great Gray Owl were found to be eating at a higher trophic level in Alberta than what the literature predicts. Stable isotope analysis should be used in conjunction with more traditional diet study methods which help to explain stable isotope analysis values, while isotope results reduce the biases associated with traditional methods.