Colonial Nesters in a Deteriorating Habitat: Site Fidelity and Colony Dynamics of Lesser Snow Geese

Birds that exhibit a high degree of natal and breeding philopatry and normally breed in stable environments may suffer costs of philopatry if their habitat deteriorates. Female Lesser Snow Geese (Chen caerulescens caerulescens) are highly site faithful; however, recent increases in numbers of breeding birds have resulted in widespred habitat destruction in some colonies. Using capture-recapture modeling techniques on multiple resightings of marked individuals, we examined whether breeding-site fidelity of adult Snow Geese has changed over time in a colony that has grown rapidly and in which habitat quality has declined severely during the past two decades. In addition, we examined the age structure of breeding birds to investigate natal-site fidelity to formerly central areas of the colony. Only slight changes in adult breeding-site fidelity were detected over 10-year periods, despite the deterioration of nesting and brood-rearing habitats in and near the investigated areas. However, increasing mean ages of breeding birds in formerly central areas of the colony indicated a lack of recruitment into those areas; young birds must have preferred to settle at the colony periphery even when vacant spaces in the center were available. Together with a small amount of movement by adult birds, the settlement pattern of young birds has led to a long-term shift in the colony location as a whole.