Forest Bird Communities in the Apostle Islands of Wisconsin

The bird populations of 24 stands of forest vegetation on the Apostle Islands of Lake Superior were censused by a sample count method. A two-dimensional ordination of the stands was constructed, based on the avifaunal similarities between stands. The ordination represents an environmental complex, within which many bird species are distributed in definite patterns. Certain vegetational characteristics of the stands also show well-developed patterns within the ordination, indicating that they may play an important role in the environmental complex. Aspens, pines, hemlocks, maples, and the relative amount of coniferous understory show excellent patterns. The species of birds observed in the study are discussed in relation to their apparent environmental preferences. Two species found in every stand, the Ovenbird and the Red-eyed Vireo, have broad environmental tolerances. Two others found in at least three fourths of the stands, the Black-throated Green Warbler and the American Redstart, are partial to mature forests, the former especially to birch--hemlock, and the latter to pine as well. In pioneer aspen growth, White-throated Sparrows and Mourning Warblers are most abundant. There are greater similarities between stands on the same island than would be expected from the vegetational variation. The possible influences of island size and of the behavior of birds in relation to island topography are discussed.