Fig. 2. Temporal and spatial variability in bird species abundance and community metrics. Variance is expressed as coefficients of variation. Temporal variance refers to within-site temporal variance calculated using data collected near Calling Lake, Alberta, Canada from 1993 to 1998 using 20 point-count stations per site and four surveys per year. Spatial variance refers to between-site initial variation calculated using BBS (Breeding Bird Survey) data (from the closed boreal forest physiographic region of Alberta) collected from 1992 to 1998. The horizontal and vertical lines dissecting the plot represent mean between-site initial variation and median within-site temporal variation, respectively, across all species, excluding those with maximum within-site temporal variation (2.449). Median within-site temporal variance was used because of the skewed distribution of the parameter across species. An extreme and a moderate example were selected from each of the four variance categories delineated by the plot for inclusion in the efficiency analysis, for a total of eight species. The four-letter codes identify the eight species and three community metrics selected as targets for simulation studies: BCCH, Black-capped Chickadee Parus atricapillus; BGNW, Black-throated Green Warbler Dendroica virens; BHCO, Brown-headed Cowbird Molothrus ater; GRJA, Gray Jay Perisoreus canadensis; PIWO, Pileated Woodpecker Dryocopus pileatus; WBNU, White-breasted Nuthatch Sitta carolinensis; WTSP, White-throated Sparrow Zonotichia albicollis; YWAR, Yellow Warbler Dendroica petechia; SR, species richness; GN, richness of the ground-nesting guild; SW, Shannon-Weiner diversity index.