Bird niches in a subalpine forest: An indirect ordination.

Multivariate techniques that are tolerant of the curvilinearity in population responses can be used to ordinate bird species in a niche hyperspace and to quantify niche relationships. Multidimensional scaling, secondary reciprocal averaging, and reciprocal averaging followed by principal components analysis give similar results in an ordination of 20 bird species in a spruce-fir forest. The ordination represents the organization of the bird community in relation to niche axes and suggests grouping of the bird species into guilds. A group of foliage-gleaning insectivores that finely divide their resource base is central to the bird community; other groups of species (ground feeders, aerial feeders, conifer specialists, and bark probers and peckers) have broader niches.