San Luis National Wildlife Refuge (NWR)

The San Luis NWR is managed as part of the San Luis NWR Complex.


Riparian Woodlands

Riparian habitats – along rivers and sloughs – largely consist of woodlands dominated by willows, cottonwoods, and oaks. These habitats with their multi-layered structure provide nesting habitat for colonial-nesting waterbirds such as egrets, herons, and cormorants, as well as many species of raptors. The largest density of breeding songbirds are found in these areas. These habitats also serve as movement corridors for many wildlife in the Central Valley.


Wetlands comprise a quarter of all Complex lands. Wetlands include permanent marshes which contain water year-round and are dominated by robust water-loving vegetation such as cattail and bulrush. These dense stands of reed provide ideal nesting habitat for coots, grebes, blackbirds, bitterns, ibis, and marsh wrens. Seasonal marshes are the prevalent wetland type throughout the Complex. These seasonal wetlands contain water from early-autumn through spring. Dominant vegetation includes swamp timothy, smartweed, millet, dock, and sedges – all of which provide a valuable food source for wildlife. These seasonal wetlands attract large numbers of ducks, geese, shorebirds, and other waterbirds.


Uplands at the Complex comprise three-quarters of the landbase and include grasslands and croplands. Grasslands are the most common and are dominated by annual and perennial grass species. These uplands provide habitat for a host of herbivorous wildlife including elk, black-tailed deer, desert cottontail rabbits, black-tailed jackrabbits, and voles. Common songbirds include western meadowlarks, savannah sparrows, and horned larks.

Vernal Pools

Vernal pools are seasonally-flooded depressions in impermeable soils that hold rainwater until evaporation occurs. The pools are home to specialized plants and animals adapted to the alternating wet/dry regime. Most vernal pools on the Complex are found at the Kesterson and West Bear Creek Units of the San Luis NWR and the Arena Plains and Snobird Units of the Merced NWR.

Refuge Nature Trails

  • Two trails that launch from the visitor center

    • the Upland trail (.5 mi.) and

    • the Wetland/Riparian trail (1 mi.).

  • Situated along the auto tour routes are

    • the Chester Marsh trail (1 mi.),

    • the Sousa Marsh trail (1 mi.), and

    • the Winton Marsh trail (.5 mi.).

The Chester Marsh trail is open seasonally from February 15 through September 15, and takes visitors to a historic ferry crossing on the San Joaquin River.

The Sousa Marsh trail includes an elevated observation platform overlooking one of the largest wetlands on the Refuge, which provides spectacular waterbird viewing fall through spring.

The Winton Marsh trail meanders around a permanent wetland and includes an elevated observation platform.

Other units in the San Luis NWR Complex include the Merced NWR, San Joaquin River NWR, and Grasslands Wildlife Management Area. The Refuge Complex headquarters is located at the San Luis NWR: 7376 S. Wolfsen Road, Los Banos, CA 93635. Contact us by phone at 209/826-3508 or mail at PO Box 2176, Los Banos, CA 93635.