Although several new species have been discovered during the past decade most of the world's bird species are known and, next to mammals, birds are one of the best studied groups of organisms. Because it encompasses a transition between prairie and savanna regions of the Central Plains and mixed conifer-hardwood forests of the Noorthern Lake States, Wisconsin supports particularly diverse opportunities for birdwatchers. Grassland birds are especially diverse in southern Wisconsin, eastern deciduous forest birds occur throughout the state, and boreal species are present in the north. Wetland species are well represented in places such as lower Green Bay, Horicon Marsh , the Mississippi River floodplain, and Crex Meadows State Wildlife Area . Birds are important elements of nearly every ecosystem on earth.
Many plants depend on birds for pollination and seed dispersal.
Specialized interactions between hummingbirds and flowering plants, for example, illustrate the vital role of birds in our environment. In the Great Lakes Region, Blue Jays are the major long distance disperser of acorns, helping oak trees colonize new sites. Many other trees and shrubs produce fruits which ripen during fall movements of migratory birds like thrushes, tanagers, catbirds, grosbeaks, sparrows, and warblers. Finally, bird predation plays a significant role in regulating populations of insects, rodents, and other animals, some of which are serious human pests.