Habitat Relationships

RESEARCH APPROACH

To study rail-habitat relationships, we collect data on wetland habitat characteristics such as wetland size, water source, geomorphic setting, water regime, hydrology, plant species diversity, vegetation cover and degree of grazing. We then use statistical models to determine if the presence of Black Rails is correlated with any of these habitat characteristics. We also use high-resolution digital imagery from the IKONOS satellite and topographic information from digital elevation models (DEMs) to map wetland habitats across the Sierra foothills.

WHAT WE HAVE LEARNED

In the Sierra Nevada foothills, Black Rails occupy a very specific habitat type, generally shallow zones (<3 cm depth) of permanent or semi-permanent wetlands with dense emergent vegetation. Due to their highly secretive behavior, Black Rails rarely venture out into the open but instead prefer to remain hidden beneath a canopy of thick cattails, rushes, sedges or wetland grasses. A steady flow of shallow water also seems to be important to Black Rails in the foothills, hence their association with artificial wetlands that form, either deliberately or accidentally, near irrigation canals. Black Rails can occupy wetlands as small as 40’ x 40’ but are usually found in wetlands that are a quarter of an acre or larger. Black Rails are sensitive to wetland vegetation clearing and overgrazing.