IMPACTS OF HIGH POPULATIONS ON GEESE AND OTHER FAUNA

Effects on the Geese Themselves

Lesser snow geese from Hudson Bay have experienced declines in adult and gosling body size, gosling survival (Cooch et al., 1991a,b; Williams et al. 1993) and increases in parasites (Rockwell et al. 1994). Greater snow geese have declined in body size (Reed and Plante 1997). J. Leafloor (unpublished data) and M. Hill (unpublished data) have found that adult and gosling interior Canada goose from Akimiski Island, NWT exhibit morphological variation from area to area that is consistent with the hypothesis of reduced forage resources resulting from high populations of geese.

Effects on Other Birds

The effects on other birds have not been studied. Nesting birds in the vicinity of goose colonies where severe damage has occurred experience direct loss of nesting habitat through the destruction of sedge, grass and low shrub associations. In addition, the changes to soil salinity and decomposition processes likely result in significantly altered microfaunal changes resulting in a loss of forage resources. Preliminary findings (B. Milakovic and R . Jefferies, unpublished data) suggest that aquatic invertebrates may be less diverse and less abundant in ponds in areas of degraded vegetation.

Gratto-Trevor (1994) monitored local nesting populations of Semipalmated Sandpipers (Calidris pusilla) and Red-necked Phalaropes (Phalaropus lobatus) at La Pérouse Bay, Manitoba. Nesting pairs of both species have declined dramatically in habitats traditionally occupied by relatively high densities of lesser snow geese for nesting and brood rearing over the last 30 years. Impacts of the growing snow goose colony on habitat quality of these shorebirds was cited along with weather and predation rates as possible explanations. The Yellow Rail (Coturnicops noveboracensis) was formerly abundant at La Pérouse Bay, but has not been encountered there recently (R. Rockwell, unpublished data). Other shorebirds, ducks (e.g., American Wigeon, Anas americana, and Northern Shoveler, Anas clypeata) and passerines, (e.g., Lapland Longspurs, Calcarius lapponicus) are likely candidates for similar negative interactions because they share either nesting or brood rearing habitats. Some species appear to be utilizing degraded environments. For example, where willows have died and little vegetation remains, Semipalmated Plovers (Charadrius semipalmatus) breed. The scale of the problem and associated level of risk to the broader populations requires intensive study, including some calculation of the proportion of total range of the species affected by goose damage. It is clear, however, that the interaction is dynamic, and the rapid occupation of new areas by geese increases the threat to other species even as the effects are being calculated.

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