Fine-scale spatial structuring in cackling Canada geese related to reproductive performance and breeding philopatry

Cackling Canada geese, Branta canadensis minima, have a geographically structured pattern of relatedness at both local and large spatial scales. Here, I investigated the potential mechanisms that may be responsible for promotion and maintenance of genetic structuring; specifically, I examined the relationships between breeding philopatry, the proximity of relatives and nesting success. Using eight microsatellite loci, I genetically identified individual female cackling Canada geese nesting on the Yukon-Kuskokwim Delta in western Alaska between 1994 and 1997. I found that 50-70% of the nests in any one year were of females that had nested on the study area in a previous year. Successful females were 3.8 times more likely to return to within 150 m of a previous nest site (breeding philopatry) than unsuccessful females. Relatedness of the nearest neighbour also had a positive but small effect on breeding philopatry. Breeding philopatry and relatedness of the nearest neighbour, in turn, increased future nesting success of females. These results suggest that patterns of fine-scale genetic differentiation are associated with reproductive success and increases in success coupled with breeding philopatry may further promote fine-scale genetic structuring.