Birds that nest in marshes are the least understood birds in Missouri. One reason for this is the difficulty of entering marshes, especially in summer. We know even less about other marsh inhabitants or the intricate relationships that play out within these lush, aquatic systems.
Of Missouri's natural communities, marshes are the richest. Compared to upland grasslands and forests, marshes in summer produce the most animal biomass per unit area in the least amount of time. They also provide the greatest number and assortment of niches for wildlife. Marshes could be called "nature's cities" because their abundant resources allow their residents to pack densely together.
Marshes are low-lying tracts of land that hold water throughout much of the year. They are dominated by rooted, perennial, non-woody vegetation that emerges above the water's surface. Marshes support perennial, water-loving plants, such as bulrushes, spike rushes, arrowheads, burreeds, cattails, water lilies and pickerel weed. Many of these plants provide marsh birds with nesting habitat and cover. The presence of water during much of the year protects eggs and nestlings from land-dwelling predators.
In Missouri, marshes were once common in our river floodplains, especially along parts of the Missouri and Mississippi rivers. Under natural conditions, new marshes are always forming while others are silting in. In the last century, however, Missouri has lost as much as 90 percent of its wetlands. Modern control of our big rivers prevents new marshes from forming, and existing marshes have been drained at an accelerated rate.
To obtain more information about marsh birds, Missouri Department of Conservation biologists periodically coordinate surveys of selected marshes with ornithologists, conservation area managers, U.S. Fish and Wildlife Service biologists and interested citizens. These marsh bird surveys began in the early 1980s and are conducted semi-annually.
The surveys begin by playing taped calls to provoke birds to respond. Some species answer the tapes more readily than others. Some are more likely to call after dark, and others are unlikely to answer at all. To pinpoint respondents and locate non-callers, surveyors walk parallel courses in patterns that allow them to cover much of the marsh. They record the number of nests they locate, including the species using them, the number of eggs or young, the water depth and the type of vegetation supporting the nest.
Typically, surveyors target about two dozen marshes during the May-through-June survey period. Most of the marshes are on Conservation Department areas and national wildlife refuges. Most