PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Variable impact of nest predation in a changing boreal forest landscape.
Warkentin, Ian1, Thompson, Randy2, Flemming, Stephen3, 1 Memorial University, Corner Brook, NL, Canada2 Gros Morne National Park of Canada, Rocky Harbour, NL, Canada3 Atlantic Service Centre - Parks Canada, Halifax, NS, Canada
ABSTRACT- Declines of forest-nesting songbirds in North America have been linked to the anthropogenic fragmentation of forest habitats. One presumed mechanism behind these declines is the increased loss of eggs and young to predators as fragmentation and the related amount of edge increases. While especially evident in agriculture-dominated landscapes, the same cannot be said for forestry-dominated areas, particularly in the boreal forest. The latter is curious given the common occurrence of gray jays (Perisoreus canadensis) which prey upon the eggs and nestlings of songbirds through focused foraging along natural and anthropogenic edges. We used artificial nests to assess patterns of loss to predators in naturally fragmented and harvested landscapes with contrasting amounts of edge (both natural and cut) and local forest cover. As expected, ground nests were overwhelmingly subject to predation by mammals, particularly mice; while gray jays were the dominant depredators of tree nests. During the two years of the study, small mammal populations grew exponentially and pine marten (Martes americana) populations also significantly increased. Still, patterns of nest predation by mammals were not associated with any measure of landscape fragmentation in either year. Conversely in year one, gray jay depredation rates were positively linked to the amount of logging in the surrounding area and the general amount of local non-forested area (natural and harvested), as well as the amount of edge associated with logging. In the second year, gray jay predation was inversely associated with the amount of natural non-forest cover (bogs) and bog edges. While gray jays did behave as expected in the first year, responding strongly to increased fragmentation and its associated effects; the relationship did not hold in the second year. Thus, our study suggests that gray jays may have some influence on the productivity of nesting songbirds, but their behavior and influence is not consistent among years, indicating that they may not be a major driver of productivity patterns for songbirds in this region of the boreal forest.
Key words: forestry, songbirds, nesting, predation