Colma Creek Public Shore

Spring Summer Fall Winter

Panorama of Colma Creek Public Shore/SAMTrans Marsh, March 2009 (Joe Morlan)


Colma Creek Public Shore (a.k.a. Colma Creek Mouth, a.k.a. SamTrans Peninsula) is an area that was part of the bay's historical mudflats and tidal marshes. It is fed by Colma Creek, which has its headwaters on San Bruno Mountain, flows west toward Daly City, then is buried underground to reemerge in a concrete channel in South San Francisco. The creek returns to a natural bed as it crosses under San Mateo Avenue. Fed by every storm drain along the way, it reaches the bay behind the SFO Airport Costco. Part of this area was dug out in WWII for shipbuilding. Looking at the remnant piers now, this is hard to imagine. Due to the creek's trip across the Peninsula, Colma Creek Mouth is one of Save The Bay's top 10 trash hot spots. A large feature of Colma Creek Public Shore is SamTrans Peninsula, which apparently was once an island called Belle Aire Island, but is now a bus yard.

The best time to go is at low tide and stay for mid-tide, or mid-tide and stay for low tide. Avoid early morning, when the sun is low in the east. All trails are wheelchair accessible. Bikes and dogs are allowed.

From the parking area at 195 Belle Aire Road (behind Costco), cross the bridge over the creek. Turn right on the north shore and walk along the path with the creek on your right. You will see a variety of ducks, Canada Geese, shorebirds, gulls, grebes, loons, perhaps a Clapper Rail. In the weedy field to your left, there are sparrows, finches, starlings, mockingbirds, and Western Meadowlarks. From several areas along the trails, you can look south to the United Air Lines maintenance facility. In the A of the sign is a Peregrine Falcon nest, which is occupied in the spring. As you go farther north, the mudflat will open out and you will see more waterfowl. In fall and winter, there are large rafts of ducks in the bay. Depending on the tide, you will see shorebirds such as Western Sandpiper, Dunlin, Black-bellied Plover, Willet, Whimbrel, Marbled Godwit, Long-billed Curlew, dowitchers (usually Long-billed), and gulls: California, Western, Ring-billed, Short-billed, and Glaucous-winged. To get closer to the shorebirds, you walk north until the path turns right, and continue east as far as you want. On the return trip, pay attention to the lawn and trees behind 360 Littlefield, where you will see House Finches and warblers. Detour onto the gravel path that parallels the buildings. The weedy field will be on your left. In this area, Ron Thorn has found a number of interesting migrants, such as Prothonotary Warbler, Brewer's and Clay-colored Sparrow, and Palm Warbler.

For SamTrans, park at Safe Harbor, or preferably the 8-car lot outside Park SFO (195 North Access Road). Walk alongside the old shipbuilding docks to the peninsula, then take the fitness trail around the island. We usually go clockwise. In the mudflat between SamTrans and the old piers you will find shorebirds, gulls, ducks, and blackbirds. In the trees outside the bus yard fence are Yellow-rumped Warblers in season. Check the old docks for herons and egrets, gulls and cormorants, stilts and avocets. If the tide is out, check the plants along the opposite shore for large flocks of Willets, Marbled Godwits, and Whimbrels, camouflaged among the reeds. Continue to the point. This will be the coldest spot on the entire trip. It is as far out into the bay as you can get on this walk, and will afford views of all the activity on the mudflats. If there are rails about, they will be in this section. From the point, return the way you came, or continue along the east side of the island. The birds on the Bayside will be slightly different. White-crowned Sparrows will flee ahead of you in the bushes alongside the trail. A large marshy field is a favorite gathering area for Canada Geese.

Look For These Birds

Canada Goose, Mallard, American Wigeon, Blue-winged Teal, Cinnamon Teal, Northern Shoveler, Green-winged Teal, Canvasback, Northern Pintail, Greater Scaup, Lesser Scaup, Surf Scoter, Bufflehead, Common Goldeneye, Barrow's Goldeneye (uncommon), Ruddy Duck, Pied-billed Grebe, Western Grebe, Clark's Grebe, Eared Grebe, Horned Grebe, American White Pelican (uncommon but expected here), Brown Pelican, Double-crested Cormorant, Great Blue Heron, Great Egret, Snowy Egret, Black-crowned Night-heron, Turkey Vulture, Osprey, White-tailed Kite, Northern Harrier, Sharp-shinned Hawk, Cooper's Hawk, Red-tailed Hawk, American Kestrel, Merlin (uncommon here), Peregrine Falcon, Ridgway's Rail, Virginia Rail, Sora, American Coot, Snowy Plover (uncommon here), Black-bellied Plover, Semipalmated Plover, Killdeer, Black-necked Stilt, American Avocet, Greater Yellowlegs, Willet, Lesser Yellowlegs, Whimbrel, Long-billed Curlew, Marbled Godwit, Sanderling, Western Sandpiper, Least Sandpiper, Dunlin, Short-billed Dowitcher, Long-billed Dowitcher, Wilson's Snipe, Red-necked Phalarope, Bonaparte's Gull, Short-billed Gull, Western Gull, California Gull, Herring Gull, Glaucous-winged Gull, Ring-billed Gull, Caspian Tern, Forster's Tern, Elegant Tern (fall), Rock Pigeon, Mourning Dove, Anna's Hummingbird, Barn Owl, Belted Kingfisher, Black Phoebe, Say's Phoebe, American Crow, Common Raven, Tree Swallow, Northern Rough-winged Swallow, Barn Swallow, Bushtit, House Wren, Marsh Wren, Ruby-crowned Kinglet, American Robin, Northern Mockingbird, European Starling, Orange-crowned Warbler, Yellow Warbler, Yellow-rumped Warbler, Common Yellowthroat, California Towhee, Savannah Sparrow, Song Sparrow, Lincoln's Sparrow, White-crowned Sparrow, Golden-crowned Sparrow, Dark-eyed Junco, Red-winged Blackbird, Western Meadowlark, Brewer's Blackbird, House Finch, Lesser Goldfinch, American Goldfinch, House Sparrow

Rarities Seen Here

In this guide, "rarities" are defined as those species given an County Abundance Code of 4, 5, or 6.

Cackling Goose (2015, 2016, 2018), Greater White-fronted Goose, Harlequin Duck, Long-tailed Duck, Red-necked Grebe, Least Tern (2013), Common Tern (2022), Black Skimmer (2001, 2022), Semipalmated Sandpiper (2020), Pectoral Sandpiper (2012), Ruff (2021, 2022), Red Phalarope, Tropical Kingbird (2013, 2014, 2015), Sedge Wren, Palm Warbler (2011), Prothonotary Warbler, Canada Warbler (2021), Swamp Sparrow, Clay-colored Sparrow (2009, 2022), Brewer's Sparrow, Vesper Sparrow (2017), Lark Sparrow, White-throated Sparrow (2019), Nelson's Sharp-tailed Sparrow


On the east side of Hwy 101, north of the San Francisco Airport, take North Airport Blvd. to Belle Air Road and turn east, toward the Bay. At the end of the road is a parking area between the Water Quality Control Plant and Costco.
For SamTrans parking, continue east on North Access Road and turn left onto SamTrans North Road, and left into the parking lot for Safe Harbor. Park in the spaces marked for Public Shore parking.

Parking is also available at the end of Haskins Way, off E. Grand Avenue, and just outside the Long Term Parking garage for the airport; there is a turn off North Access just past the entrance to the garage. If you are coming from the airport, you can access the marsh by taking the Long Term Parking shuttle bus.

Interactive Map

Red Markers: Parking Area or Trail Head
Hover mouse pointer over marker, or click marker, for identification.






Safe Harbor is a homeless shelter. We have never had any problems with the guests, but recommend, as in all parking situations, that you not leave anything valuable visible in the car.


Restroom at Costco for members (or you talk your way in, as the food court does not require membership). Because of the proximity to the airport, there are many mini-marts and gas stations within two miles of this site.


Avian Research Status

There is an active study of Clapper Rails being conducted under the auspices of the USGS Western Ecological Research Center, that includes radio-tagged rails at Colma Creek.

Colma Creek Mouth is the named hotspot for this area in eBird. Coverage has been good, with twenty-eight of forty-eight calendar quadrants showing data, for 112 species. Help complete the year-round picture of this environmentally sensitive spot by entering your sightings in eBird.

The San Francisco Bay Bird Observatory (SFBBO) is conducting a long-range study of gull movements in the Bay Area. California Gulls have been leg-banded with plastic colored bands. If you see any of these gulls, please note the leg and the color of the band; if it is possible to read the number on the band, record that also. This information can be shared directly with Carly at SFBBO ( If the birds also have a metal band, and you can read that number, too, please report that to the National Bird Banding Lab.

Sequoia Audubon has led one field trip to Colma Creek mouth and SAMTrans.

Additional Photos

The Marsh in the Midst of Industry, Colma Creek Public Shore, March 2009 (Sonny Mencher)

The bird that most resembles a football with wings, Ruff! September 2021 (Dorian Anderson)

A Black-bellied Plover, enroute to full alternate plumage, Colma Creek Public Shore, March 2009 (Sonny Mencher)

Peregrine Falcon at United Airlines Hanger, Colma Creek Public Shore, March 2009 (Sonny Mencher)

Canada Goose landing, Colma Creek Public Shore, March 2009 (Sonny Mencher)

Hooded Mergansers, Colma Creek Public Shore, March 2009 (Sonny Mencher)

Author: Laurie Graham, Uploaded: April 6th, 2009
Last Update: October 31st, 2022, 8:25am

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