Wetland Land Management

This past weekend, as I was driving across the causeway that runs over the wetlands between Davis and Sacramento I saw that the ponds at the north end of the Yolo Bypass National Wildlife Refuge were flooded!  This is in preparation for the coming massive migration of waterfowl through the central valley of California that occurs each winter.

Managing land for waterfowl and other wetland bird species requires a lot of planning.  One of the most common strategies is something called Moist Soil Management.  In this technique, water levels are changed throughout the year to maximize the amount of plant grow that will benefit migrating birds.  Generally, this means that the water is slowly drained off in early spring.  The land is usually disked or plowed to aerate the soil to provide the best growing conditions.  The land is then left alone for the spring and summer to allow plants to seed and grow.  By altering exactly when the draw-down of water occurs, undesirable plant species can be discouraged in favor of plant species that produce food and cover for waterfowl.  These species include rice, millet, ragweed, and smartweed. Like many grasses and crop species, these plants can grow in very dense expanses.  To break up such areas, patches are frequently ploughed into the stands of plants to create a more heterogeneous habitat with dense areas of cover, edges or patches, and open spaces all mixed together.  Such habitats provide a great deal of high quality habitat for wetland birds.  Then, usually sometime between the first of September and the first of October, water is allowed to start to flow back in to flood the low-lying areas.  The flooding process is slow, and the whole area may not be flooded until as much as six weeks after the process began.  Most dabbling ducks feed by picking seeds and other food items off the bottom of a pond, so good ponds do not have to be deep, 18 inches or less, to attract birds.  Once the water has been brought back in, the area will remain flooded until the birds leave to head back north to their breeding grounds.  But even during the fall and winter, water levels are not static.  Changing how deep different areas are the impact of feeding waterfowl can be spread across all available land.

So, as you can see, managing land for migratory birds is a pretty involved process.  It is certainly a full time job, and research is continuously going on to figure out the best ways of creating the best possible habitats for the millions of birds that migrate to or through California each fall.  Seeing the water returning to the area is one of the more dramatic steps in the annual cycle of a managed freshwater wetland, but it is by no means the only step needed in the creation of high quality habitat.