BROOD MOVEMENTS AND DISTRIBUTION OF EASTERN PRAIRIE POPULATION (EPP) CANADA GEESE (BRANTA CANADENSIS INTERIOR) IN NORTHERN MANITOBA: POTENTIAL INFLUENCE OF INCREASED SNOW GOOSE (CHEN CAERULESCENS CAERULESCENS) ABUNDANCE

In 2001 and 2002, we conducted aerial surveys to compare indices of Eastern Prairie Population (EPP) Canada goose (Branta canadensis interior) brood distribution and abundance near Cape Churchill, Manitoba with those obtained in 1977 and 1978. Since the late 1970s, many of the coastal salt marsh areas used for brood-rearing have been degraded as a result of increased foraging pressure from locally breeding and migrating light geese [snow geese (Chen caerulescens) and Ross’s geese (C. rossii)] and the density of nesting Canada geese has declined. The mean Canada goose brood density across the entire survey area in 2001-2002 was not different from 1977-1978 (difference between means ± 95% CI; 0.20 broods/km2 ± 0.36); however, the mean brood density in the southern portion of the survey area was significantly higher in 2001-2002 than in 1977-1978 (0.45 ± 0.39). In 2002, the mean snow goose brood density was higher than the mean Canada goose brood density (27.31 ± 10.92), with higher densities of snow geese in northern coastal flats/beach ridge areas and higher densities of Canada geese in southern coastal flats/beach ridge areas. The mean number of Canada goose broods observed on 15 traditional brood-rearing areas decreased since 1977 (-8.67 ± 6.19) and the mean number of snow goose broods observed increased (43.91 ± 38.22). Canada goose broods appear to have shifted use of brood-rearing areas in response to reduced food availability, direct interactions with snow geese on brood-rearing areas, or both. Loss and degradation of brood-rearing habitat may be a factor in declines in nest density of Canada geese and has implications for EPP management