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◆ Don Edwards San Francisco Bay ◆

National Wildlife Refuge

TIDELANDS TRAIL

Length: 1.3 miles

Time: 1 to 2 hours

Rating: Easy

Regulations: Pets are permitted only on the Tidelands Trail and must be leashed at all times. Pets are prohibited inside the visitor center and elsewhere on the refuge.

Facilities: Visitor center with helpful staff, interpretive displays, books, maps, and information about guided nature walks and other programs; picnic tables, water, toilet, phone.

Directions: From Highway 84 at the east end of the Dumbarton Bridge in Fremont, take the Thornton Ave./Paseo Padre Parkway exit, and go south 0.5 mile to Marshlands Road, the refuge entrance. Turn right and go 0.5 mile to a stop sign, then left into the parking area. The trailhead is at the west side of parking area, just below the large flagpole.

This easy loop, with habitat ranging from upland to salt marsh, is a perfect introduction to the amazing variety of plants and animals, especially birds, found in the refuge. Fall, winter, and spring, when bird populations are highest, are the best times to visit; avoid afternoons, when wind and glaring sunlight may make viewing difficult. Binoculars and/or a spotting scope, along with bird and plant guides, are recommended. Consider also taking one of the guided walks, offered by refuge personnel and volunteers, which concentrate on either birds or plants. (Coyote Hills Regional Park is just north of the refuge, across Highway 84; it would be easy to explore both areas on the same day.)

As you walk up the stairs from the west side of the parking area toward the visitor center, you pass a native plant garden containing coyote brush, black sage, toyon, and bush monkeyflower. When you reach a T-junction with a paved path, turn left and continue uphill to the visitor-center entrance, passing eucalyptus, coast live oak, and coast silk tassel on the way. After exploring the visitor center, with its many exhibits, books, and other publications, walk back outside to an observation area overlooking San Francisco Bay.

Looking southwest, the section of the refuge in front of you extends roughly to the middle of the Bay, and includes salt ponds enclosed by levees, as well as Newark Slough, a river of tidewater flowing through the salt marsh just below the visitor center. Salt ponds, remnants of an extensive salt industry that flourished here in the mid-1800s, still exist on the Bay today. Water moves from pond to pond via channels, the salinity concentrates through evaporation, and the highly saline water is eventually processed into salt.

This is our nation’s largest urban wildlife refuge, with more than 20,000 acres of open space set aside to protect wildlife. Three hundred species of birds and other wildlife, including a number of threatened and endangered species, live here year-round or pass through on migration. The refuge extends from Newark to Alviso and contains a variety of habitat, including open water, salt ponds, mudflats, salt marshes, and upland areas. The refuge was renamed to honor Don Edwards, a congressman from San Jose, now retired, who was instrumental in creating and then expanding the refuge through Congressional acts.

Tidelands Trail, bridge over Newark Slough.

Walking uphill from the visitor center, you follow the self-guiding Tidelands Trail, a loop that will take you through an upland area, beside a salt marsh, across Newark Slough, and along the shore of a salt pond. Gaining elevation on a gentle grade, you can see east to a large salt marsh bordering Marshlands Road, a good area to search for shorebirds on a rising or falling tide. As you climb to a high point, you pass some of the plants growing on the refuge, including toyon, California sagebrush, curly dock, pearly everlasting, and California buckwheat.

A few hundred yards from the visitor center you reach a fork. Going left takes you uphill to an observation deck perched on a bluff overlooking Newark Slough; staying right bypasses the bluff. Bear left, and when you reach the observation deck via steps on your right, take a moment to enjoy a 360-degree view that encompasses much of San Francisco Bay, one of the world’s great wildlife areas. Approximately 250 species of birds can be found here, including more than one million shorebirds and waterfowl that use the Bay as a wintering area. Descending from the observation deck on a gentle grade that soon steepens, you pass some picnic tables and then the bypass trail, merging from the right.

As you descend, the route bends left and heads toward the marsh. Shorebirds, terns, ducks, and grebes are the main avian attractions of this refuge, but there are other birds to watch for, including raptors, hummingbirds, and songbirds. A dried fennel stalk may offer a perch for the tiny Anna’s hummingbird, while the tall spike of a century plant may hold a white-tailed kite. Descending past beautiful acacia trees, which bloom in mid-winter, and a grassy area brightened by yellow Bermuda buttercups, you reach the edge of the marsh, flooded at high tide, where a trail joins from the left.

As the route turns right and heads toward the Bay, you pass a trail heading left into the marsh. Tide and time of year will determine the level of bird activity here, especially for shorebirds, a tribe that includes oystercatchers, avocets, stilts, plovers, willets, curlews, godwits, small sandpipers, dowitchers, and phalaropes. Most of these birds breed elsewhere, usually during May and June, and arrive here as either migratory visitors or winter residents. Some shorebirds, however, including American avocets, black-necked stilts, and snowy plovers, a threatened species, nest in the marshes around San Francisco Bay.

At low tide, shorebirds will be dispersed along the many miles of mudflats around the Bay that provide fertile feeding grounds, and at high tide, rising water will force them to congregate in elevated roosting areas, just above the flood. Thus a rising or falling tide is best for viewing shorebirds. If shorebirds are present, you are almost certain to see one of their tribe called a willet. With its long legs and long bill, this large, drab gray sandpiper transforms itself in flight into a thing of beauty, flashing a bold black-and-white wing pattern as it skims low over the marsh.

As you begin to climb through a rocky area with outcrops of serpentine, California’s state rock, you pass some large century plants, residents of southern California, whose tall stalks offer perches for winged hunters in this treeless part of the refuge. At a rest bench, the route levels and bends right, leading you to another observation deck.

Here the route forks, the right-hand path staying level and the left-hand path dropping past a tangle of blackberry vines to a bridge over Newark Slough. Descend to the bridge, which makes a great vantage point for observing birds as they fly over the marsh and swim in the slough. You can also study the marsh plants—pickleweed, cord grass, salt grass, alkali heath—spread out below and adapted in varying degrees to their salty surroundings. In the late summer and early fall, marsh gum-plant sports bright yellow flowers, pickleweed adds touches of red and magenta, and dodder, a parasitic plant, paints everything it touches a garish orange.

After crossing the bridge, you reach a T-junction with a dirt path running along the top of a levee next to a salt pond. If the pond is flooded, you may see shorebirds such as western and least sandpipers, dunlin, and black-necked stilts scampering along its edge, probing for invertebrates or picking brine flies off the water’s surface. Turning right, you come to a picnic table and another observation deck, a good vantage point from which to observe the Bay’s salt ponds.

Although definitely a drastic alteration of the natural habitat, salt ponds have created a unique environment, similar to saline Mono Lake in the eastern Sierra, that supports a breeding population of American avocets, black-necked stilts, phalaropes, and snow plovers, along with California gulls and Forster’s terns. (Because of the snowy plover’s threatened status, Marshlands Road beyond the visitor-center parking area is closed from April through approximately the end of August).

Endangered species, such as brown pelicans, peregrine falcons, least terns, clapper rails, and salt marsh harvest mice, call the refuge home or pass through on migration; despite habitat loss, they have survived thanks to efforts by conservationists, scientists, and government agencies. Other animals that used to roam the Bay Area, such as grizzly bear and tule elk, are no longer found here.

Stories of the Bay’s huge supply of waterfowl attracted sportsmen and market hunters to these marshes beginning in the late 1800s. A low red hunting shack, right, was built in the 1930s by Joe Pine of Niles, California, and was occupied by him until the 1960s. A nearby sunken blind, left, offers a hidden site for bird observation and photography. Just past the blind, the route turns right to cross Newark Slough on a long wooden bridge. (The Newark Slough Trail, a 5-mile circuit, starts here and follows the slough west into the marsh.)

Partway across the bridge, another shack, left, has a picnic table and information about the creatures—brine flies and brine shrimp—that live in salt ponds. Once across the bridge, you switchback right, passing a trail leading left to a small amphitheater used for outdoor meetings and programs, and climb to an observation deck flanked by picnic tables in the shade of a eucalyptus. At a T-junction you turn left, joining the path coming from above the first bridge. As you come over a low rise, you reach the paved path leading right and uphill to the visitor center. With the large flagpole directly ahead, follow a dirt-and-gravel path straight to the parking area.