Among the many elements of biodiversity in boreal forest ecosystems, birds are among the most conspicuous vertebrates. Because they typically occupy particular habitats, they may be sensitive to management activities such as forestry that cause habitat change. I used point samples to estimate bird abundance in young (30 yr), mature (100 yr) and old ($>$180 yr) spruce-dominated forest in the Rocky Mountain foothills of Alberta during the spring of 1991 and 1992. A total of 46 bird species was observed, with an average of 5.5 species per 10 minute sample, but differences in species richness among age classes were not significant. Many species rarely were observed in any age class, but of the 10 bird species for which the statistical power to detect differences among age classes was high, all but two (Gray Jay and Yellow-rumped Warbler) differed in abundance among age classes. Only one species, Winter Wren, was observed consistently more often in old forest. As a group, permanent residents were observed more frequently in old forest, while most long-distance migrants were observed in young forest. Cluster analysis of average habitat attributes suggested that species could be grouped according to broad habitat affinities, and principal components analyses suggested that at least two species, Brown Creeper and Winter Wren, were associated with old forest habitats. Although further research is required to explain the apparent affinity of Winter Wrens and Brown Creepers for old forest, maintaining these species in this region likely will require a continued supply of old forest habitats.

I used the data from the above study plus comparable data obtained in 1990 and 1992 to test habitat suitability models for Varied Thrush, Ovenbird and Red Squirrel. Model performance varied and the relationships between abundance and a single habitat variable were frequently obscured by correlations with other variables. Suggested revisions to each model are suggested based on the patterns observed in this study. However, conceptual problems associated with the use of habitat suitability models make it difficult to apply them to the problem of maintaining habitat diversity in managed forest ecosystems, and alternative strategies are suggested.