The Implications Of Agriculture In Interior Alaska For Population Dynamics Of Canada Geese

Abstract

Understanding how environmental change affects demography is essential for understanding and managing populations. An anthropogenic change in the environment that has affected wildlife populations is widespread agricultural development. Agriculture has both negatively and positively impacted abundance of species by affecting a variety of vital rates that influence population abundance. In this study, I describe the migration ecology of Canada geese (Branta canadensis) that nest and stage in Interior Alaska. I also describe how the introduction of agriculture has potentially positively impacted population dynamics of Canada geese by increasing nutrient acquisition, thereby improving their fecundity and survival. Two subspecies of Canada geese used Interior Alaska for staging and at least partially segregated themselves during spring and fall staging. I documented a difference in survival between two age classes of Canada geese, primarily lesser Canada geese ( B. c. parvipes), and attributed it to the higher susceptibility to harvest of hatch-year (HY) geese. Estimates of annual survival of Canada geese in this study are among the lowest, and estimates of recovery rates are among the highest, for a migratory population of geese, likely due to behavioral traits and habitat selection that make lesser Canada geese more susceptibility to harvest. Survival of after-hatch-year (AHY) female Canada geese was positively associated with the amount of endogenous nutrient reserves females had at the time of banding in fall. An experimental manipulation of nutrient reserves, however, suggested that the association between nutrient reserves and survival results from variation in individual quality (not measured), not a direct relationship between nutrient reserves and survival. Female geese in our study gained fat and minerals, but not protein, during spring staging. Fall staging geese had fat levels greater than or equal to spring staging geese, suggesting fat reserves are important during early fall staging in this population of geese. Although I concluded that the introduction of agriculture has likely increased fecundity and decreased natural mortality in Canada geese that stage and breed in Interior Alaska, I also concluded that mortality due to harvest is sufficient to offset those changes, preventing an increase in the population.