Watch the Birdies at Wildlife Refuge

San Francisco Bay National Wildlife Refuge is a big one, befitting the West Coast’s most crucial bay and marsh tidewater, salt ponds and mudflats. At more than 23,000 acres, it’s one of the nation’s largest urban wildlife refuges, a critical habitat for more than 250 species of birds.

Thirty miles of trail trace the bay shore. Some of these pathways use the tops of levees to cross mudflats and salt ponds. (Note that the levees are created of mud dredged from the bay and are sometimes closed for repairs or for the seasonal use of nesting waterfowl.) Interpretive paths, with trail-side panels, offer easy-to-follow information about the bay’s fish, fowl and coastal ecology. One refuge trail even travels to Coyote Hills Regional Park.

Tidelands Trail is a wide levee-top interpretive path that visits marsh and bay wetlands. Bay views are grand from a crow’s nest observation platform. Tidelands, honored with national recreation trail status, loops around Newark Slough, visits a salt company pump house turned picnic site, and offers a duck blind from which to photograph birds.

Begin your walk at the attractive visitor center perched on a rise near the eastern approach to the Dumbarton Bridge. Pick up a map and inquire about the refuge’s ambitious schedule of guided walks and interpretive programs.

Directions to trail head: Drive east over Dumbarton Bridge. After the toll plaza, exit on Thornton Avenue. Turn right and drive a quarter-mile to Marshland Road, then turn right to the visitor center.

The walk: Join the path at the overlook behind the visitor center. Check out the view of the bay and wetlands from the crow’s nest observation platform.

Tidelands Trail descends to the edge of the marsh, then crosses a bridge over Newark Slough and intersects the Newark Slough Trail (an excellent five-mile round-trip hike if you have the time) and joins a levee. You stroll pass Leslie Salt Co. salt evaporator ponds, home to brine shrimp and the birds that eat them.

Nearby is a salt industry pump house built on pilings over the water; it’s now a unique picnic shelter. After recrossing Newark Slough via another bridge, the trail returns to the visitor center.

McKinney’s book “Day Hiker’s Guide to Southern California” is available through The Times for $16.45 (including tax, shipping and handling) by calling (800) 246-4042.

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Tidelands Trail

WHERE: San Francisco Bay National Wildlife Refuge.

DISTANCE: 1.5 miles, round trip.

TERRAIN: Mudflats, marshes.

HIGHLIGHTS: Cloe-up of San Francisco Bay ecology.

DEGREE OF DIFFICULTY: Easy.

FOR MORE INFORMATION: San Francisco Bay National Wildlife Refuge, P.O. Box 524, Newark, CA 94560; tel. (510) 792-0222.