Summer habitat use and behaviour of Greater Snow Geese Anser caerulescens

Abstract

We studied habitat use by Greater Snow Geese in a glacial valley on Bylot Island, Northwest Territories, the most important breeding site for this population. The valley contains a mosaic of polygon wetlands surrounded by upland tundra. Twelve habitat types were identified based on physical features, and the floristic characteristics of each was sampled and described. Daily visual surveys were conducted from 11 July to 16 August 1990 in a 14 km area. Habitat used, group size and behaviour were recorded for all adult-plumaged geese. Wetland habitats were grouped into two classes, pond/lake and we meadow, and all other habitat types were classified as upland. Plant species composition was similar in the two wetland classes with a dominance of graminaceous plants (Dupontia fisheri, Carex aquatilis and Eriophorum spp.). Both families and non-parental geese significantly preferred all habitats with ponds and lakes throughout the summer, probably because of the high quality food and the protection from predators conferred by these habitats. However, there was a shift toward greater use of wet meadow habitats in the latter half of the season. Although upland habitat was avoided, it was used at a low level throughout the summer by families. Because both families and non-parental geese shifted simultaneously, the shift is probably related to reduced food availability in the preferred habitats rather than changes in gosling size or physiology. Time spent foraging was relatively constant across habitat types and was approximately double (60%) for non-parental compared to parental adults (30%). Adults with young were alert approximately 20% of the time compared to less than 3% for non-parental birds.