AVIAN HABITAT SELECTION AND PRAIRIE WETLAND DYNAMICS - A 10-YEAR EXPERIMENT

Northern prairie wetlands play a vital role in the life cycle of a wid e array of bird species. Prairie wetlands used by birds span the entir e range from shallow ephemeral ponds inundated for short periods each spring to large permanent water bodies that seldom, if ever, go dry. T he objective of this study was to determine the response of blackbirds , waterfowl, and American Coots to changes in habitat structure induce d by water level fluctuations in prairie wetlands. The study was condu cted on a series of experimental marshes within the Delta Marsh in sou thern Manitoba, Canada. Water levels were adjusted following a predete rmined schedule to simulate the wet-dry cycle of prairie marshes. Aeri al photographs were taken annually, and habitats were characterized us ing Geographic Information System (GIS) techniques. Weekly avian censu ses were related to habitat features using Principal Components Analys is (PCA) procedures. Yellow-headed Blackbirds selected shallowly flood ed habitats with a mixture of open water and emergent vegetation, whil e Red-winged Blackbirds were found in shallower areas with dense veget ation. Coot habitat was consistent over the seasons. They preferred de epwater habitats with interspersed vegetation. As a group, dabbling du cks were generally found in hemi-marsh conditions (equal amounts of co ver and water in an interspersed pattern) throughout much of the year. Some species moved to deeper, more open habitats during the fall seas on. As a group, diving ducks chose areas with deeper water and less ve getation than dabbling ducks. However, there was considerable variatio n among diving duck species, with Canvasbacks using hemi-marsh sites i n spring, and Ruddy Ducks and Lesser Scaup using the most open sites f ound on the study areas. The wet-dry cycle characteristic of prairie m arshes presents a wide array of habitat conditions for avian species. Although hemi-marsh conditions during the cycle result in maximum use for a large number of species, they do not meet the requirements of al l species in all seasons. Conservation programs should include wetland complexes of varying water depth and flooding duration to ensure the widest array of habitat types for avian species.