Although our major goal throughout the book has been to relate bird habitat use to wetland resources and features, birds that can directly affect a wetland ecosystem by their influence on vegetation and thereby bird habitat have an impact on other birds directly or alter ecosystem processes that may induce change within the entire system (Table 11.1).

Because of their mobility, birds facilitate movement of invertebrates to established wetlands that have lost their population via drought (Swanson 1984), as all invertebrates do not have eggs that can survive long periods without water (Wiggins, MacKay and Smith 1980). Birds also transport invertebrate eggs to newly created wetlands such as strip-mine ponds or river-formed wetlands. Common herbivorous crustaceans like amphipods have been especially prominent in studies of the plumage of hunter-killed or live waterfowl in both Europe and North America, but snails, snail eggs, and other macrocrustaceans have also been noted in plumage. One cannot wade in wetlands without experiencing invertebrates and seeds clinging to boots, so it is no surprise that birds (and also beavers and muskrats) carry them as well. Plant materials such as seeds and foliage of submergent plants are commonly found in or on the plumage of herbivorous ducks and coots. One study reported seeds of 12 saltmarsh plants, most of which had special adhesive devices or systems, carried by ducks (Vivian-Smith and Stiles 1994). This helps to explain a gradual increase in richness that occurs over time in wetland developed on strip-mined lands, where plant “seed banks” are minimal (McKnight, 1992). In such cases, wetland seed banks from 5- to 7-year-old ponds are commonly used to establish vegetation in newly created wetlands.