Wetlands are especially known for their abundance of some species or groups of birds as well as for their diversity of species not found elsewhere. The major reason for this abundance presumably is the availability of resources produced by the great primary productivity of wetlands. The diversity of species undoubtedly is linked to diversity of resources produced in the many microhabitats resulting from water-depth gradients and fluctuations. The range of spatial scales we can examine was outlined above, but I would like here to focus on factors that influence bird use within and among wetlands. Although the emphasis is on geographical, and physical or structural patterns in wetlands, this includes structural aspects of live components such as plants (Table 8.1). Plants vary in life form or physical stature, which, with water distribution, creates visual patterns useful to us as indicators of wetland types and conspicuous to birds as indicators of various essential resources. We will first consider the range from homogeneity to heterogeneity that can exist in certain wetland types, forming within-wetland variation of habitats (microhabitats), and then consider larger-scale relationships among wetlands or wetland complexes or regimes, which can best be appreciated by first understanding the patterns found in individual wetlands.

Vegetation life form

Wetland types differ in the height, diameter, and robustness of dominant plants as well as in the range of plant species diversity, which with variation in water regimes can result in highly variable and sometime quite complex patterns of habitat diversity.