Birding is best from fall through spring. Generally, the shorebirds and ducks stay in Charleston Slough and near the pumphouse in Coast Casey Forebay, while the rails and marsh birds stay in the reeds and reed-encircled ponds in Coast Casey Forebay.

In fall, Virginia Rail and Sora arrive at the forebay and can be found with the resident Common Gallinules at the “Hidden Pond” (located on the south side of the forebay and accessed from a narrow dirt trail there) and at a small pond on the north side of the forebay (viewed from the “Speed Limit 15” sign). Lesser Yellowlegs are also found in the forebay in the fall and can be found in the “Hidden Pond” and in the marsh at the northeast corner of the forebay. Elegant Tern can occasionally be found on the pilings on the nearby Salt Pond A1, which borders Charleston Slough. Many shorebirds are also present in Coast Casey Forebay near the pumphouse and in Charleston Slough near the observation deck.

In winter, many ducks and shorebirds are present in the area. Cinnamon Teal can sometimes be found in the small pond on the north side of the forebay, Canvasback can be found on Salt Pond A1, and the two rails are usually still present in the same areas in Coast Casey Forebay. Walking along the Adobe Creek Trail (north of the forebay) at dusk may bring a sighting of a Short-eared Owl flying over the Palo Alto FCB, although they are usually found from Byxbee Park on the other side of the FCB. Black Skimmer may be present in Charleston Slough at this time, but are much easier to see in the spring and summer when they return to their breeding colony at Shoreline Lake and occasionally make foraging visits to the slough and forebay.

In spring, the ducks and rails usually leave, but many migrating shorebirds arrive and stay briefly before leaving for the summer. Western Sandpiper is very common and can be seen from the observation deck at Charleston Slough with various other shorebirds. Cliff and Barn Swallows also arrive, and nest near the pump house.

The Santa Clara Valley Audubon Society has additional tips for birding Charleston Slough and Coast Casy Forebay.

Black Skimmer, Common Gallinule, Virginia Rail, Sora, Cinnamon Teal, Lesser Yellowlegs, Elegant Tern, various ducks, and shorebirds

Charleston Slough and Coast Casey Forebay are two expanses of mudflats and marsh located in Mountain View. They are both directly west of Shoreline Lake, and a trip to the slough and forebay is best combined with a trip to the lake.

Charleston Slough is a large tidal area that has good amounts of mudflats at low tide and is similar to a large channel at high tide. Coast Casey Forebay is a smaller area to the south of the slough and has mudflats near the pumphouse in the northwest corner, a reed-filled marsh in the center areas, and several small ponds in the northeast corner. Although you can loop entirely around the forebay, only the west and south sides of Charleston Slough are publicly accessible. The north, east, and west sides of the forebay have paved trails, while the south side only has a small dirt trail. The west side of Charleston Slough has a large gravel trail.

There are several hotspots in the area. The Charleston Slough/Coast Casey Forebay hotspot should be used only for those two areas, the Salt Pond A1 hotspot should be used for the salt pond and pilings, and the Shoreline Park-Shoreline Lake area should be used for the lake and lawns to the north of the lake.

The parking lot is on Terminal Boulevard in Mountain View, just south of the forebay. There is a good amount of parking here, but it can fill up quickly. The restrooms are just past the trailhead at the start of the parking area (near the southwest end of the forebay).

Adobe Creek Loop Trail, Coast Casey Forebay Loop Trail

The AllTrails website has a description and map of a hike at Charleston Slough.