Book Description

Coastal wetlands in the Laurentian Great Lakes undergo frequent, sometimes dramatic physical changes at varying spatial and temporal scales. Changes in lake levels and subsequent changes in the juxtaposition of vegetation and open water greatly influence biota that use coastal wetlands. Several regional studies have shown that changes in vegetation and lake levels lead to predictable changes in the composition of coastal wetland bird communities. We report new findings of wetland bird community changes at a much broader scale, covering the entire Great Lakes. Our results indicate that water extent and interspersion increased in coastal wetlands across the Great Lakes basin between low (2013) and high (2018) lake-level years, although variation in the magnitude of change occurred within and among lakes. Increases in water extent and interspersion resulted in a general increase in marsh obligate and marsh-facultative bird species richness across the basin. Species like American bittern, common gallinule, American coot, sora, Virginia rail, and pied-billed grebe were significantly more abundant during high water years. Lake Huron and Lake Michigan showed the greatest increase in water extent and interspersion among the five Great Lakes, while Lake Michigan showed the greatest increase in marsh-obligate bird species richness. These results suggest that effective management, restoration, and assessment of wetlands must account for fluctuations in lake levels. Although high lake levels generally provide the most favorable conditions for wetland bird species, variations in lake levels and bird species occurrences produce an ecosystem that is both spatially and temporally dynamic.