The effect of Great Lakes water level fluctuation on northern Michigan wetland bird populations.

Abstract

Throughout the world, diverse avian populations continuously utilize wetlands. The abundance of the resources, including shoreline habitat and food, has resulted in bird species that are adapted exclusively to this habitat and others that use this habitat only during portions of their life cycle or during migration. Today, we witness many adaptations which maximize benefit from this semi-aquatic life style, including: anatomical and morphological adaptations (including rear leg placement for swimming, bone and lung modifications for diving, water resistant plumage), adapted feeding tactics, modified migratory flight paths, and life history adaptations (Weller). These adaptations have created a dependency upon wetland habitat availability for sustained population levels. The effect of birds on wetland habitat is critical for the ecosystem. They are responsible for seed dispersal of many plants, and also for the dispersal of many invertebrates. In addition to the transfer of seeds and organisms, the birds have an effect on many wetland soils through their waste products, which can serve as nutrient deposits (WB). Birds are also critical to wetlands because they draw the attention of humans to the environment. Many critical pieces of wetland legislation have resulted from the pressure of waterfowl hunters who are concerned with the decline in habitat and the potential ramifications on their recreation. They are also critical to local economies, and then residents may choose to maintain wetlands for their recreational value rather than convert them for another use. Groups such as Ducks Unlimited and Audubon are able to work on a national level to preserve wetlands. In northern Michigan, coastal marshes nurture a diversity of plants and animals. The variance in perennial Great Lakes' water levels has sustained a myriad of plant species. With the long-term cycling of low and high water levels, many changes in micro-habitat occur which result in a shift of the entire biotic community. Plants are directly affected by nutrient availability and water saturation, thus becoming good indicators of many chemical and geophysical properties of the soil in the immediate area surrounding them. Bird populations are directly affected by plant presence and by the availability of insects, invertebrates, small mammals and other birds, which makes them an indicator of the entire productivity of an ecosystem (Weller). The cycling of water levels also has effects on the macro-habitat by significantly affecting the amount of shoreline which is nesting and foraging habitat for birds and therefore the bird populations. This effect was studied through the observation of bird species diversity and abundance at several northern Michigan coastal marsh sites and was compared to historical recrods to determine if Great Lakes' water levels had an effect on bird species diversity and abundance.