East Bay Trails. David Weintraub

godwits, small sandpipers, dowitchers, and phalaropes. In just a few minutes you may see a fine assortment, including black-necked stilts, American avocets, long-billed curlews, marbled godwits, dowitchers, and sandpipers, along with other water-loving birds such as egrets, ducks, and gulls. In the grassland areas, watch for resident savannah sparrows and blacktail jackrabbits.

      Once you reach the shoreline, in about 0.8 mile, the route turns north and runs along the water. From here you have terrific views, on a clear day, of San Francisco, Oakland, the Bay and San Mateo bridges, the Oakland and Berkeley hills, Mt. Diablo, and Mt. Tamalpais. If the tide is out, you will see shorebirds during most of the year, feeding on the mud flats at the edge of the Bay. Some species, such as American avocets and black-necked stilts, breed in the Bay Area, but many others fly north in May and June to breed in Canada, Alaska, and the Arctic, which accounts for their absence from our area during those months. But during the rest of the year, and especially in winter, San Francisco Bay hosts one of the largest concentrations of shorebirds in North America, sometimes more than one million strong. The Bay is also the most important stop on the Pacific Flyway, the aerial route between northern breeding grounds and wintering areas in southern California, Mexico, and Central and South America.

      As you turn north, the route crosses another slough, whose water passes under a short bridge and makes several jogs on its way around the west edge of Hayward Marsh. Two of the most common marsh plants, pickleweed and cord grass, are evident here. Pickleweed, a low-growing plant with many stubby branches, thrives in the middle marsh, where it is moistened only briefly by the tide’s salty flow. Light green in spring and summer, pickleweed brightens marshes in the fall as it turns red and purple, but winter finds it dull brown. Cord grass, 1 to 4 feet tall and dark green, lives low in the marsh and is well adapted to twice-daily flooding by the tide. Cord grass, like other plants, is an air purifier, consuming carbon dioxide and carbon monoxide, and releasing oxygen into the atmosphere. The orange threads that you may see wound in the pickleweed is salt-marsh dodder, a parasitic plant.

      After walking about a mile, you reach a junction with a path going right, which you will use later on your return. But for now, turn left and return to the shoreline at Johnson’s Landing, a cove with a small beach and breakwater. John Johnson began harvesting salt from San Francisco Bay by putting levees around natural pools in the marsh. This landing, like others along the shoreline, was built in the 1850s for boats that carried salt, waterfowl, agricultural products, and passengers to San Francisco.

      As you turn north and continue walking along the water’s edge, a sweeping view of the Alameda County shoreline stretches before you all the way to Oakland. This part of the route is also a segment of the San Francisco Bay Trail, which uses existing trails and roadways owned and maintained by various public agencies and will some day encircle the Bay. More than half of the Bay Trail’s proposed 400-mile route has been completed. On your right is Cogswell Marsh, named in honor of Dr. Howard L. Cogswell, a well-known Bay Area shorebird biologist, educator, and member of EBRPD’s board of directors from 1971 to 1982. This large marsh consists of several former ponds restored to tidal action by an EBRPD levee-breaching project completed in 1980.

      A birder checks area near Cogswell Marsh for shorebirds.

      Soon you reach the first of two bridges that span breached levees in this section of the shoreline. Here is an excellent vantage point from which to study shorebirds feeding on the mud flats below. Time your arrival just after high tide, when the water begins to recede and more and more of the flats are being continuously exposed. Different shorebirds have evolved different strategies for feeding, from the avocet’s side-to-side swiping motion, to the dowitcher’s rapid, machine-like drilling. The largest North American shorebird, the long-billed curlew, probes deep in the mud for small clams using its long, down-curved bill. The bird will then rinse off its muddy prize before swallowing it whole.

      After crossing the first bridge, continue north, with the Bay on your left and the salt marsh spreading out to your right. Soon the route turns right, away from the bay, and heads east. On your left is a large inlet, with the second bridge ahead. On a rising tide, shorebirds feeding in the shallows of this inlet are pushed toward shore, so this is another great vantage point for observing their antics. And because you are facing north as you look out across the inlet, the sun is behind you for most of the day, another plus when viewing birds. Across the Bay to the northwest, the light-colored buildings of San Francisco are thrown into relief by the dark background of Mt. Tamalpais.

      At the second bridge, after you’ve had your fill of birding, turn right and begin your return trip along a dike with a slough and salt marsh to the left. (If you want a longer hike, cross the bridge and follow the route northeast, then west to Triangle Marsh and Hayward’s Landing.) Check the slough for ducks; especially pretty are ruddy ducks in bright plumage. After walking south for about 0.5 mile, turn right on a dike leading back to the bay. If the tide is coming in, especially just before sunset, you may see large flights of shorebirds coming to roost in Hayward Marsh, left. Soon you rejoin the original route near Johnson’s Landing; turn left here and retrace your route to the visitor center.

      ◆ Coyote Hills Regional Park ◆

      This is one of the most user-friendly of the East Bay parks. It has a visitor center with informative displays and helpful staff; a lovely, shaded picnic area; rewarding but not-too-taxing trails; ample opportunity for nature study; and a rich history dating back thousands of years. Children will enjoy the Muskrat Trail, a self-guiding nature walk through the park’s Main Marsh, as well as special cultural programs presented by descendants of Native Americans who lived in this area for more than two thousand years. There is a paved pathway, the Bayview Trail, which circles the Coyote Hills on a mostly level course, and connects at its north end with the paved Alameda Creek Trail.

      The Coyote Hills themselves are the tips of an ancient mountain range, composed of iron-rich Franciscan chert, which lies between the Hayward Hills, east, and the Coast Range on the west side of San Francisco Bay. Mud, gravel, and silt washed down from the Hayward Hills created the flat plain at the Bay’s southern end. One of the best views of this area is from the summit of Red Hill, just a few minutes from the visitor center. At the end of the last ice age, when sea levels rose and the Bay filled, the Coyote Hills became islands. Gradually, sedimentation deposited by Alameda Creek created marshlands around the islands—on the west side, a salt marsh; and on the east, a marsh flooded with freshwater from the creek.

      Wetland areas in the park today consist mostly of brackish marshes, dominated by cattails and bulrushes. These areas provide important habitat for many species of birds and aquatic animals. The Coyote Hills bird check list, revised in 1990, contains 210 species in more than 40 categories, including grebes, pelicans, cormorants, herons, egrets, geese, ducks, raptors, shorebirds, gulls, terns, and songbirds. One wetland area, called the DUST (Demonstration Urban Stormwater Treatment) Marsh is a research project, begun in the early 1980s, to study the effectiveness of using marshes to remove pollutants from urban runoff.

      Coyote Hills Regional Park was opened to the public in 1968, and the area has a colorful history. The building that today houses the visitor center served in the 1960s and early 1970s as a lab where Stanford Research Institute scientists studied seals and other marine animals. (After the park opened, tours of the lab for the public were arranged.) In the 1950s the building served as an Army barracks for Nike missile crews; the missiles themselves were atop the hills.

      Like other regional parks, Coyote Hills has a long ranching history, going back to an 1844 land grant establishing Rancho Potrero de los Cerritos (“Pasture of the Little Hills”). This 10,000-acre parcel, owned by Augustin Alviso and Tomas Pacheco, included land that became today’s 978-acre park. After California became a state in 1850, the U.S. Congress allowed challenges to the land-grant system, and many owners were forced to sell their land to pay legal fees; this fate befell the rancho. One of those who purchased a part of the rancho was George Washington Patterson, who eventually came to own nearly 6000 acres of farm land, including the current park. The Patterson