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 i f their habitat deteriorates. Female Lesser Snow Geese (Chen caerulesc ens caerulescens) are highly site faithful; however, recent increases in numbers of breeding birds have resulted in widespread habitat destr uction in some colonies. Using capture-recapture modeling techniques o n multiple resightings of marked individuals, we examined whether bree ding-site fidelity of adult Snow Geese has hanged over time in a colon y that has grown rapidly and in which habitat quality has declined sev erely during the past two decades. In addition, we examined the age st ructure of breeding birds to investigate natal-site fidelity to former ly central areas of the colony. Only slight changes in adult breeding- site fidelity were detected over 10-year periods, despite the deterior ation of nesting and brood-rearing habitats in and near the investigat ed 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 periph ery even when vacant spaces in the center were available. Together wit h 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.