Spring at San Francisco Bay National Wildlife Refuge

0 Comments | Oakland Tribune, Jun 6, 2009 | by Aric Crabb

Winter storms give way to sunshine and longer, warmer days as spring arrives at the San Francisco Bay National Wildlife Refuge complex.

The U.S. Fish and Wildlife Service established the refuge 35 years ago as the first urban national wildlife refuge in the country. Spring brings new life to the seven refuges of the complex, which protects both the wildlife and their habitats.

In a small saltwater marsh nestled alongside homes and businesses in East Palo Alto, a secretive bird appears during a warm April evening. As the tide pushes into the marsh, the California clapper rail forages along the mud bank of a small slough lush with pickleweed. With a few steps into the dense vegetation, it is gone.

A staggering 80 percent of tidal marsh in the Bay has been lost to development, agriculture, freshwater runoff and other urban encroachment. This has been disastrous for species such as the endangered California clapper rail. One of the largest rails, this hen-like bird has seen population numbers dwindle through the years because of hunting and habitat loss. Figures from the National Audubon Society show that the population has dropped from about 5,000 in the mid-1970s to fewer than 1,000 in 2007.

The Antioch Dunes evening primrose and the Contra Costa wallflower have managed to keep their roots planted in the ancient dunes formed along the San Joaquin River after the Mojave Desert receded in prehistoric times. Petals from their flowers shine with color as they stretch out of the sand and toward the spring sun.

What were once 100-foot windblown sand dunes are now two small units that make up the 67 acres of the Antioch Dunes National Wildlife Refuge. This is the last place on the planet where these two endangered flowers and the Lange's metalmark butterfly are found in nature and kept from going extinct.

Along the beach at the Salinas River refuge a male western snowy plover runs along the sand looking for flies to fill its stomach. It is nesting time for these small, sparrow-sized birds that the U.S. Fish and Wildlife Service has listed as threatened since 1993.

Habitat loss and increasing predator populations have brought down the number of western snowy plovers through the years.

"By protecting snowy plovers and therefore the sandy beach habitat and old salt ponds that they inhabit, we are protecting a shrinking ecosystem that is unique and essential to the survival of a number of native insects, birds, mammals, plants and reptiles," said biologist Jenny Erbes, of PRBO Conservation Science. As a biologist for the nonprofit, Erbes will spend day after day at the refuge during breeding season studying and banding snowy plovers in an effort to help manage the population. So far this year, six of the 19 plover nests have been lost at the Salinas River refuge, including what is believed to be the first nest lost to a raven there.

Breeding season survey numbers from the U.S. Fish and Wildlife Service show about 1,123 western snowy plovers along the Pacific Coast in 2008, with 133 plovers in the Bay Area. One has decided to make her nest in the middle of an old salt pond along Highway 84. Her partner goes off in search of food after taking the night shift on the nest. The female settles over the three eggs she has laid in a small depression next to some old mussel shells. If all goes well, these eggs, just about 10 days old, will hatch in the coming weeks.

Not all chicks will be so lucky. Not long after the sun rises over the San Pablo Bay refuge, a predator makes off with an egg from a nest, leaving it broken in half along Tolay Creek. Over a levee at the Cullinan Ranch unit of the refuge, a red-winged black bird takes exception to a male northern harrier cruising low along the brush looking for a meal. The red-winged blackbird repeatedly divebombs the larger hawk, chasing it from over a marsh where a female mallard keeps close watch over the 10 ducklings in her brood.

At the Warm Springs unit of the Don Edwards San Francisco Bay National Wildlife Refuge, the small amount of winter rain may not be enough to help the endangered tadpole shrimp or the threatened California tiger salamander that use the seasonal vernal pools. But as the pools have dried under the spring sun, endangered Contra Costa goldfields have sprouted up through cracks in the dried mud and bloomed at the vernal pool sites.

Spring has brought new life for plants, animals and insects that rely on these wildlife refuges for their survival. We can only wait to see what the summer months bring to this urban oasis.