Distinguishing migratory and resident Canada geese using stable isotope analysis

Effective management of Canada geese (Branta canadensis) requires a reliable method to determine the population affiliation of geese in the harvest. We determined if stable isotope analysis of feather tissue could distinguish between migrant and resident populations. We obtained feather samples of migrants from Atlantic population of Canada geese in northern Quebec near Ungava Bay, Canada. We grouped resident population Canada geese as coastal residents and inland residents according to the habitats where they were captured in New Jersey. We analyzed for isotopes of carbon (delta C-13), nitrogen (delta N-15), and sulfur (delta S-34). We found significant differences among migrants, coastal residents, and inland resident for all 3 isotopes. Combinations of isotopic ratios for the 3 elements resulted in unique patterns among groups of geese. We entered the isotopic ratios into a discriminant analysis using collection site as the grouping variable (migrants, inland residents, and coastal residents). We formed 2 significant functions that discriminated among the 3 groups 92% of the time. The first function accounted for most of the variance, and was highly influenced by the isotope ratios for carbon and sulfur. The results indicate that stable isotope analysis of primary feathers can provide a reliable means to discriminate between migratory and resident populations of Canada geese. Stable isotope analysis is a promising technique for identifying the breeding areas of Canada geese, but additional studies are needed to determine inherent variability over broad geographic areas.