Kin clustering in barnacle geese: familiarity or phenotype matching?

We investigated the settling pattern of barnacle geese Branta leucopsis that returned to breed in their natal colony. Females nested close to their parents and sisters, but settling of males conformed to a random pattern. The apparent preference for breeding close to kin in females could be a by-product of extreme philopatry to the natal nest site. However, sisters also nested close to each other when settling on a different island than the one where their parents bred, pointing at a genuine preference for breeding close to kin. Females only nested close to sisters born in the same year (i.e., sisters that they had been in close contact with). This suggests that the clustering of female kin in barnacle geese does not result from phenotype matching. We did not detect any direct benefits of settling close to birth site or kin, but the analyses lacked power to detect small benefits of proximity to kin given the many other factors that may influence breeding success. Colonially breeding birds share characteristics that are generally believed to promote the evolution of cooperation, yet kin clustering and kin selection have been little studied in this group. Future research should be directed to studying the possible roles of kin clustering and kin selection in the evolution of coloniality.