FACTORS AFFECTING NESTING SUCCESS IN GREATER SNOW GEESE - EFFECTS OF HABITAT AND ASSOCIATION WITH SNOWY OWLS

We examined how habitat features affected nesting success of Greater S now Geese (Chen caerulescens atlantica) on Bylot Island, Northwest Ter ritories, Canada, under high (1993) vs low (1994) nesting success and colonial vs isolated nesting (1994 only). Because Snow Geese nested in association with Snowy Owls (Nyctea scandiaca) in 1993, we also exami ned the relationship between nesting success and distance from owl nes ts. Predation, especially by Arctic foxes (Alopex lagopus), was the ma in cause of nesting failure on Bylot Island. In 1993, goose nests near an owl nest had better success than those farther away, and they also tended to be initiated earlier. Few habitat features were related to nesting success, although nests located in pond habitat had lower succ ess than those in wet meadows or moist tundra. In 1994, Snowy Owls wer e absent, and goose nesting success was much lower than in 1993 (23-42 % vs 90%). Isolated nests located on hillsides had higher success than those located in lowlands. In contrast, colonial nests were more succ essful in lowland wet meadows, where tall willow bushes (Salix lanata) were present, than in either moist tundra or hillsides. In the latter habitat, nests associated with Cassiope tetragona, a plant that typic ally grows in depressions between hummocks, had higher success than th ose associated with other vegetation. We conclude that nesting in asso ciation with raptors, such as Snowy Owls, that maintain a predator-fre e area around their nest, was probably a dominant factor affecting Gre ater Snow Goose nesting success. In the absence of owls, isolated nest s had higher success in hilly habitats than in lowlands, whereas colon ial nests in tall willows were most successful.