Wetlands represent one of the richest, if not most variable, life zones in the country. Comprised of a myriad of types ranging from large lakes to fragile quaking bogs and wooded swamps to open marshlands, wetlands are difficult to characterize in a few broad brush strokes. All wetland habitats share the common characteristic of having fresh water as a visible and dominant component, at least during some portion of the year, although changes in ground water level, as well as fluctuations in rainfall, can significantly affect the amount of water present in certain wetlands from season to season and from year to year.Because of the diversity of wetland types, a great variety of plant, bird, and other wildlife species inevitably occur in wetland habitats. In some wetlands, such as in lakes and ponds, water is standing for most of the year, while in streams and rivers it is always flowing.These differences profoundly influence what lives and grows in a particular wetland. Likewise, water depth is important. In deep water wetlands, only diving birds can readily utilize the habitat, whereas in wetlands with shallow water, emergent aquatic plants can grow, which help to support large numbers of breeding marsh birds including grebes, bitterns, waterfowl, rails, moorhens, Marsh Wrens, and Red-winged and yellow-headed blackbirds. In wooded swamps and along forested river edges a variety of forest birds, such as Red-shouldered Hawk, Barred owl, Pileated Woodpecker, Acadian Flycatcher, Northern Parula, and Prothonotary Warbler often make their home. Such forested wetland habitats are especially productive during migration because they frequently produce an interesting blend of true wetland birds amidst a variety of more upland species.Certain wetland habitats, such as those found along the Rio Grande in south Texas, or the San Pedro River in southeastern Arizona are justifiably famous for their unusual and unique bird and other wildlife associations. Similarly, the spectacular waterbed concentrations in the Florida Everglades in winter, and the enormous flocks of Sandhill Cranes along Nebraska's Platte River in spring are stunning examples of how wetland habitats support and concentrate huge numbers of birds at different times of the year. Indeed, without such habitats, a number of North America's bird species would be in peril.Regrettably, the Wetland Life Zone is perhaps in greater jeopardy than almost any other association of habitats in North America. Seemingly throughout time, wetland environments have been desecrated, either deliberately through filling and dumping, or incidentally through over-exploitation and pollution. Today, many wetland bird species are showing serious declines that are symptomatic of this wetland degradation.
