|Forested wetlands generally support a
greater variety of wildlife than nearby upland forests. Wetlands are essential
life support systems to a tremendous array of wildlife species. The variety of
forested wetlands types and the associated variation in plant communities
provide all of the essential habitat needs for species such as the wood turtle,
massasauga, water shrew, muskrat, beaver and various ducks, geese and herons.
Wetlands also provide one or more essential habitat needs for many other
species such as the tree swallow, yellow warbler, alder flycatcher, star nose
mole and woodcock.
Manipulation of wetland wildrife habitat or alteration of wildlife populations through management practices may be detrimental to wildlife. Alternatively, forest management practices can accomplish many wildlife objectives if conducted with consideration given to the principals of sound wildlife management. Objectives may be enhancing wildlife diversity or habitat, preventing destruction of habitat, providing for consumptive or non-consumptive use of wildlife or managing for a particular endangered or threatened species habitat.
Wetlands are most often identified with waterfowl and, nationwide, all wild ducks, geese, swans, herons and bitterns require wetland, vernal ponds or spring seeps for reproduction activities. The central flyway, a corridor composed of lakes, streams and wetlands scattered in a north?south direction through the central U.S., is used by millions of ducks and geese for their annual migrations because of the resting opportunities it provides. Waterfowl habitat needs change with the season, stage of life and type of waterfowl, yet the various kinds of wetlands provide for all of these habitat requirements. Wood ducks, for example, find their habitat needs in forested wetlands. In addition, one third of all U.S. bird species, about 230 out of 686 species, depend on wetlands for one or more of their life requirements. As an example, the tree swallow, while not totally dependent on wetlands, is dependent on wetlands for both nesting and feeding habitat. Red shouldered hawks prefer beaver ponds for feeding areas and woodcock make heavy use of alder thickets to search for summer earthworms.
Wetlands are important to mammals as a source of food and cover. Bears are omnivorous consumers and feed on fish, frogs and numerous berries found in wetlands. Bears are known to spend 60 percent of their time in spring and summer in forested wetlands and the remainder of their time moving between wetland areas (Newton 1988). Mink favor cover found in thickets in forested wetlands. White?tailed deer, beaver and weasel are examples of species that also utilize cover and food available in wetlands.
The rich food supply of microscopic algae and small invertebrates and the lack of predatory fish in vernal pools provides a habitat significant and sometimes critical to the continued survival of amphibians. Approximately one hundred ninety species of amphibians, including frogs, toads and salamanders, require wetlands such as vernal pools or spring seeps for reproduction activities. Some of these habitat requirements are unusual and very specific. The four-toed salamander makes its nest in the sides of sphagnum hummocks in such a way that the newly hatched salamanders fall directly into water, a condition critical to their survival. However, many other reptiles and amphibians have simply adapted to the fluctuating water levels commonly found in wetland environments.
Most freshwater fish feed in wetlands or on wetland produced foods. Wetlands in the flood plains of larger rivers provide spawning habitat for species such as bullhead, yellow perch, northern pike and muskellunge and are critical to the continued survival of these species. Yellow perch, walleye and bluegills leave open lake waters to spawn in shallow water wetlands.
Most commercial game fish use coastal wetlands as spawning and as nursery grounds. Striped bass, bluefish, salmon, menhaden and flounder are among the species of fish that depend on coastal wetlands. Shellfish such as oysters, clams, shrimp and blue crabs also depend on coastal wetlands for survival.
Although wetlands comprise only about five percent of the land area of the 48 contiguous states, almost 35 percent of the nation's threatened and endangered species either live in or depend on wetlands. Canby's dropwort is an example of an endangered plant species found in herbaceous wetlands in Maryland.
Besides the direct habitat benefits provided to wetland dependent fish and wildlife species, wetlands also provide substantial indirect benefits to wildlife. Wetlands improve water quality for fish and wildlife by serving as nutrient sinks. Wetlands tend to reduce coliform levels as a result of prolonged exposure of the bacteria to sunlight, oxygen and cool water temperatures in the slow moving waters of colder wetlands. Wetlands improve aquatic habitat by slowing water movement and allowing sediment to settle out of the water column. Wetlands provide special protective cover for some species such as the special winter cover provided to pheasants by cattails.
Additional indirect benefits wetlands provide to wildlife include drinking water sites, special feeding sites and travelways. Special feeding sites are best characterized by spring seeps, the broad, very shallow water wetlands that provide the first snow free areas in early spring and are heavily used for feeding by wild turkeys. Wooded wetlands along large streams in otherwise open country are used as travelways by migrating neotropical birds and large mammals such as bear, deer and moose when traveling between larger tracts of forest.
In northern states where prolonged winters are combined with deep snows, the population of large ungulates such as deer and moose is directly dependent on the quality and quantity of the vegetation in the wooded wetlands of the region. Wetlands with overstory conifers for thermal cover and a dense understory for a food source are used by deer throughout the winter.
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