STABLE ASSOCIATIONS WITHIN FLOCKS OF GREATER SNOW GEESE (CHEN CAERULESCENS ATLANTICA): DO THEY EXIST BEYOND FAMILY BONDS?

摘要

Understanding the nature of social groups may help explain the genetic structure of populations. Recently, a fine-scale genetic structure was found in the Greater Snow Goose (Chen caerulescens atlantica) among adults captured in different brood-rearing sites. Such a structure requires assortative pairing among birds coming from the same brood-rearing site, a process that could be enhanced if individuals maintain stable associations over time. We verified whether stable groups persisted throughout the annual cycle of this migratory species. We used an 18-year data set of females marked on brood-rearing sites in the Arctic (n = 16,060) and recaptured on those sites or resighted on the breeding, staging, or wintering grounds in subsequent years. We used a probabilistic method to compare the number of associations observed with the number expected by chance alone. Our results provide no evidence that stable groups persist in flocks during migration or in winter among adult females. However, females marked at the same brood-rearing site had a greater probability of being found nesting together or of being recaptured together on the brood-rearing area in subsequent years than expected by chance. We suggest that the latter associations are more likely due to the fidelity of females to their nesting and brood-rearing site than a consequence of the formation of stable aggregations among individuals. Our results do not support the hypothesis that formation of stable groups is a mechanism that promotes assortative pairing by allowing individuals from the same brood-rearing area to remain together during the non-breeding season in Greater Snow Geese.