A multivariate analysis of breeding bird species of western and central Canadian boreal forests: Stand and spatial effects

Abstract

We examined the abundance and distribution of 80 bird species in 101 breeding bird census plots collated from a wide range of sources in the boreal forest of western Canada. In order to examine the relative importance of stand attributes and geographical location we used Canonical Correspondence Analysis (CCA). Two-way indicator species analysis (TWINSPAN) identified seven stand groups ranging from young stands to mature mixed woods to spruce-dominated stands and finally wet sites. CCA demonstrated that hardwood and softwood composition of stands, amount of jackpine, stand age, upland versus wetland classification, and geographic location of stands explained significant variation in bird species composition and abundance. Using partial CCA analysis, we partitioned out the total variation in the species matrix as follows: i) non-spatial environmental variation: 24%; ii) spatially structured environmental variation: 3%; iii) spatial species variation that is not shared by the environmental variables: 14%; and iv) unexplained variation and stochastic fluctuations: 59%. Stand variables explained 27% of the variation in the species matrix; however, the geographical component explained only one ninth of this variation. Thus, while geographical location contributed significantly to variation in the species matrix, its overall effect was small. Our results suggest that for several boreal forest birds, useful habitat or stand association models can be based on existing forest inventory and ecosystem site classification data.