The effect of experimental fragmentation on bird community dynamics in the boreal mixedwood forest

The recent advent of widespread, industrial logging in Canada's boreal mixedwood forest has raised concerns about losses of wildife habitat. I studied the effect of fragmentation on the summer and winter bird communities in old mixedwood forest using experimental and descriptive approaches. A fragmentation experiment created isolated and connected forest fragments of 1, 10, 40 and 100 ha, each replicated three times. I sampled the bird community using point counts in summer and fixed transects in winter, before, and in each of 2 years after, forest harvesting. Fragmentation changed both the breeding and wintering bird communities. Neotropical migrant and resident birds were 6-32% less abundant in isolated patches of forest after fragmentation, although there was no overall loss of species from fragmented sites. Twenty-seven percent of species analysed experienced substantial (10-60%) population declines. In winter, resident birds were generally found in larger fragments, and in habitats containing mature coniferous trees. Maintaining connections between fragments mitigated fragmentation effects slightly during both summer and winter. While some of the fragmentation effects I documented are small, my results should be interpreted with caution. First, they are short-term and address only species richness and relative abundance. Second, the study area was embedded in a landscape where large areas of old forest are still available, which may have dampened local impacts of fragmentation. My descriptive study of the bird communities in patches of old mixedwood forest naturally isolated by a surrounding matrix of black spruce suggested that some Neotropical and resident species may experience strong population declines and local extinctions in the fragments created by forest harvesting. I conclude that, at a minimum, much larger areas of older forest 100 ha) than are presently mandated must be maintained to ensure the local persistence of vulnerable bird speciesScience, Faculty ofZoology, Department ofGraduat