About a mile south of the San Mateo Bridge, a pale spit runs out into the bay from the Beach Park Boulevard levee. It's built from clam, oyster and mussel shells, which is why it's known locally as the Shellbar. The levee path past it is a 12-foot asphalt trail with decomposed-granite shoulders and separate bike and pedestrian lanes. It has been fully open since October 2023, and the levee project reached final completion in February 2024.
The time of day you walk past the Shellbar matters less than the tide. The San Mateo County Bird Alliance's Foster City birding guide calls the Shellbar one of the best shorebird spots in the county and in all of Northern California. The guide also says the best viewing comes just before and just after high tide, from September through April, when thousands of shorebirds rest on the spit. Show up mid-afternoon on a falling tide and you mostly see shells. Show up an hour before the peak and the same stretch of levee has some of the densest shorebird roosting on the Peninsula.
October is a good month to start timing your walks. The guide says Foster City's best birding runs October through March, when water birds winter here by the thousands, and that wintering birds start arriving in early October.
Why the Birds Show Up at High Tide
The bay's shorebirds are spread out for most of the tide cycle. The guide says that on the paths along the bay, shorebirds and waders are the main attraction "particularly at low tide." That's when they're scattered across the exposed mudflats. As the water rises and covers the flats, they need somewhere dry to wait it out, and the Shellbar is where thousands of them rest. The guide describes the same pattern at the mudflats off the Mariner's Island Boulevard driving range, where hundreds of shorebirds roost at high tide in winter.
The tide matters even more at the peak itself. The guide says the large viewing area across from Marlin Street, which has no stairs, is the best place to see huge numbers of shorebirds roosting in the riprap at high tide. The birds don't all fit on the spit, so they spill onto the rocks right below the walkway.
Three Places to Stand on Beach Park Boulevard
After the levee was rebuilt, the guide lists three viewpoints within a short walk of each other:
- Tarpon Street, opposite Bowditch Middle School. This is the main access point, with a large viewing area and stairs down to the shell. You can walk the length of the Shellbar from here, heading north or south toward Belmont Slough.
- Between Tarpon and Marlin streets. A smaller stairway gives a second way down.
- Across from Marlin Street. This large viewing area has no stairs and gives the best high-tide view of the riprap.
You don't have to go down at all. The levee wall is low enough that you can see the whole Shellbar from the walkway. That's helpful, because the guide warns there are no trails on the spit itself, just raised shell beds that aren't always stable. It also asks visitors to keep their distance from the birds so they aren't disturbed. Watching from the levee covers both.
Restrooms and picnic tables are at Bridgeview Park, near the base of the bridge, and at Shorebird Park, where Beach Park Boulevard turns west. Both are close enough to the Shellbar to anchor a longer walk.
Reading the San Mateo Bridge Tide Table
The NOAA tide prediction station to use for this shoreline is San Mateo Bridge, station 9414458. Its benchmark sheet places it on the west side of the bridge. The NOAA prediction page for station 9414458 lists the times and heights of each day's highs and lows. Times are labeled LST/LDT, and heights are in feet above mean lower low water.
Here's how to plan a visit around it:
- Pick the high, not the clock. Find the day's high tides, then plan to be on the levee a little before the peak and stay a little after. That's the window the guide recommends.
- Lean toward morning when you can. The guide says the main Foster City birding areas can be covered in half a day and that morning is best. A morning high tide lines both of those up.
- Bring optics. The guide recommends a spotting scope throughout Foster City.
What's on the Spit, Month by Month
The Shellbar changes through the season, and the guide gives enough detail to build a rough calendar.
| When | What the guide says to look for |
|---|---|
| Late summer and early fall | Elegant Terns among the resting gulls and terns |
| September through April | Thousands of roosting shorebirds at high tide, including Red Knots, Black Skimmers, Willets, both dowitchers, Marbled Godwits, Dunlin, Western and Least Sandpipers, Whimbrels, Long-billed Curlews, Black-bellied and Semipalmated Plovers, and Black and Ruddy Turnstones |
| November through January | Some of the best months for bay ducks and diving birds farther out, including Canvasbacks, American Wigeon, both scaup, scoters, Ruddy Ducks, goldeneyes, Buffleheads, loons and grebes |
| Early April | Fewer birds, but some in breeding plumage, such as Black-bellied Plovers and Dunlin with black bellies and Red Knots showing some red |
Red Knots are a good bird to learn first. The guide calls the Shellbar the best spot in the county to see them, and in winter they're in basic plumage "without a trace of red." The guide also calls Black Skimmers frequent visitors, often in large numbers. Large flocks attract predators too. The guide suggests watching for Merlins and Northern Harriers working the shorebird flocks.
King Tides Make the Spit Smallest
King tides are the highest tides of the year, so they're the best version of the high-tide effect: more mudflat goes under, the Shellbar has less exposed surface, and the roosting birds are packed tighter. The California Coastal Commission lists this winter's statewide king tide dates as November 24 to 26, 2026; December 23 to 25, 2026; and January 21 to 22, 2027. It adds that Northern California locations may also see king tides on December 22, January 20 or January 23. All three windows fall between November and January, the stretch the guide names as some of the best months on this part of the bay.
The Commission's King Tides Project invites Californians to photograph the shoreline during these tides and upload the photos to its interactive map. It suggests shooting close to high tide, ideally within half an hour. It also asks photographers not to flush shorebirds or other animals sheltering above the tide line. On the Beach Park levee, that means staying on the walkway, as the bird guide already recommends.
"Fortunately, the levee wall is low enough so the entire shellbar can be viewed from the walkway without going down to the beach itself."
When the Tide Isn't Cooperating
If the high tide falls at an hour you can't make, the guide points to spots nearby where the birds don't depend as much on the tide.
Belmont Slough runs from the bay near Halibut Street and Beach Park Boulevard toward the south end of Marina Lagoon, with a paved path the whole way. Great Blue Herons, Black-crowned Night-Herons, and Great and Snowy Egrets feed there. Sea Cloud Park, reached from Edgewater Boulevard via Pitcairn, has benches at a cemented intake with good views of the slough. The guide notes Eurasian Wigeons there in winter, and Green-winged and Cinnamon Teal in spring.
Some of these viewpoints are near homes. The guide asks visitors to respect residents' privacy at all times.
For a guided outing, the San Mateo County Bird Alliance, whose county birding guide still carries the Sequoia Audubon Society name, has a fall 2026 field trip to Bair Island in Redwood City on Saturday, October 24. It's an easy, level walk for ducks, shorebirds and songbirds. The group meets at the Bair Island Trail lot of the Don Edwards San Francisco Bay National Wildlife Refuge, loaner binoculars are available, and advance registration is required. The Alliance notes that weather or air quality can cancel trips and that more outings may be added. Check the field trip schedule before you go.
If you live along the Beach Park Boulevard levee or are thinking about what it's like to live near it day to day, Julie Flouty is happy to talk about the Foster City shoreline, the stretches she knows well and how it figures into daily life here. Let's Connect.
