Sunday, March 26, 2017

Ode To The Wetland: More Than Just A Marsh

I realize this is the third post in a row I've written about California's wetlands.  But bear with me.  They are fascinating ecosystems that are both beautiful and rare (nowadays).  I'll be back to singing my praises of springtime in the desert soon! 

Wetlands and wildflowers at the West Bear Creek unit of the San Luis NWR

Yesterday, Eric and I were able to spend the afternoon exploring San Luis National Wildlife Refuge.  We drove the auto tour routes, hiked the trails and generally reveled in the beauty of spring in the Great Valley. 

In case you've never been out that way, or don't get the chance to visit any of the remaining wild corners of the valley this spring, come along with me on a little tour.

A portion of the waterfowl auto tour route at San Luis NWR

 The San Luis National Wildlife Refuge Complex is composed of several wildlife refuges in Merced and Stanislaus counties.  The San Luis, Merced and San Joaquin River National Wildlife Refuges are open to the public, but the Grasslands Wildlife Management Area, which consists of privately owned land under permanent conservation easements, is not.  Together, these refuges protect 45,000 acres of riparian woodland, wetland, grassland (or upland) and vernal pool habitat. 

This assemblage of distinct habitats represents the San Joaquin Valley's main habitat types.  As such, these protected lands are host to a wide assemblage of plants and animals, including endangered species such as the California Tiger Salamander and the San Joaquin Kit Fox.  The refuge is located within the Pacific Flyway, making it a critical stopover point and overwintering ground for a vast number of migratory birds.  Adjacent to the San Joaquin River, the San Luis National Wildlife Refuge Complex protects the largest remaining network of freshwater wetlands in California. 

Red-winged Blackbird

We begin our tour at the San Luis NWR visitor center, located at 7376 S. Wolfsen Road, Los Banos, off highway 165.  The visitor center gets guests of the refuge oriented, providing interactive displays that allow visitors to learn a little more about the area and its wildlife before venturing out. 

Grassland, beyond the tules.  Note the line of trees marking riparian habitat along the horizon.

Perhaps most obvious to the casual observer is the grassland or upland habitat.  Take the 5 mile drive along the Tule Elk auto tour route to see an example of California's grassland.  Along the way, you will see the refuge's herd of Tule Elk, an endemic species that was nearly lost to hunting and habitat loss in the 1800's.  Animals from this herd are periodically relocated to establish or join other elk herds around the state in an effort to restore the species.

Grasslands make up 75 percent of the refuge complex and are dominated by annual and perennial grasses.  Unfortunately, much of California's native perennial bunchgrasses have been lost and exotic annual grasses from the Mediterranean are now dominant.  Creeping wild rye (Leymus triticoides) and alkali sacaton (Sporobolus airoides) are two of our native perennial grasses.  These perennial grasses are green for a longer period of time each year than the exotic annual grasses we're used to blanketing California's hills in dry gold throughout most of the year.

Upland soils are often saline and alkaline in the San Joaquin Valley, a condition caused by low rainfall and an arid climate.  Plants that grow here must be adapted to these harsh conditions, like salt bushes (Atriplex spp.) and Salt Grass (Distichlis spicata).  Wildlife of the grasslands includes Mule Deer, Desert Cottontail Rabbits, Black-tailed Jackrabbits, voles, California Ground Squirrels and coyotes.  Western Meadowlarks sing from sign posts, Loggerhead Shrikes stake out high vantage points from which to search for prey, and Savannah Sparrows forage for seeds in the grass.  Burrowing Owls make their homes in burrows dug by ground squirrels, and Red-tailed Hawks soar overhead. 

Loggerhead Shrike

The 8-mile waterfowl auto tour route at San Luis NWR meanders through wetland habitats, with stops along the way at three short nature trails.  The first trail, the Chester Marsh trail, crosses a wetland before reaching the San Joaquin River and surrounding riparian habitat.  Riparian woodlands, marked from a distance by a winding line of trees, are dominated by willows, cottonwoods and oaks. 

Riparian woodlands provide a diverse habitat for a number of species, perhaps most notably birds.  High densities of songbirds can be found along riparian corridors, and living trees as well as dead standing snags provide nesting habitat for all sorts of birds.  Waterbirds, like egrets and herons, as well as raptors like hawks and Great Horned Owls nest in large stick nests.  Woodpeckers create nest cavities that are also used by cavity nesting birds, like Wood Ducks, Western Screech Owls, Western Bluebirds and Tree Swallows.  When walking through a riparian woodland, stop often to watch and listen.

Tree Swallow

The majority of the waterfowl auto tour route winds through wetlands.  Some are permanent marshes, dominated by tule reeds, while most other marshes are seasonal wetlands.  The seasonal wetlands are filled with water in the fall, kept full through spring to provide additional habitat for overwintering waterfowl, and allowed to dry out in the summer.  During the winter, Sandhill Cranes, geese, Tundra Swans and a wide array of duck species make their home in these seasonal wetlands.  Important plants of the seasonal wetlands include swamp timothy (Crypsis schoenoides), smartweed, dock and sedges, which provide food for waterfowl. 

Wetland along the Sousa Marsh Trail

The tules and cattails of permanent wetlands provide nesting habitat for non-migratory marsh birds, such as coots, blackbirds, bitterns and Marsh Wrens.  Long-legged shorebirds - American Avocets, Black-necked Stilts, yellowlegs, sandpipers and dowitchers - abound in the wetlands!  Take the time to get out and walk the trails at the Sousa Marsh and Winton Marsh, both near the end of the waterfowl auto tour route.

American Avocet

Hopefully, this little "tour" has broadened your appreciation for the Great Valley and its diverse assemblage of hidden habitats that have been largely lost to development.  The Valley is more than just something to drive through on your way from north to south; it's more than one town after another along the 99 corridor, and it's more than just rows and rows of crops.  It's a rich and thriving ecosystem, begging to be studied, explored, appreciated and protected.

Learn more about the San Luis National Wildlife Refuge Complex at its website:

No comments:

Post a Comment