About the Merced National Wildlife Refuge

512_Ross and Snow Geese_Rich Albers



 “Wild beasts and birds are by right not the property merely of the people who are alive today, but the property of unknown generations, whose belongings we have no right to squander.”
Theodore Roosevelt -- American President, outdoorsman, naturalist, and leader of the early conservation movement.


The Merced National Wildlife Refuge encompasses 10,258 acres of wetlands, native grasslands, vernal pools, and riparian areas. It was established in 1951 under the Lea Act to attract wintering waterfowl from adjacent farmland where their foraging activities were causing crop damage. In the last few decades, changes in local agricultural practices and Refuge management activities have reduced these wildlife/crop issues.

The Refuge plays host to the largest wintering populations of lesser Sandhill cranes and Ross’ geese along the Pacific Flyway. Each autumn more than 20,000 cranes and 60,000 arctic-nesting geese terminate their annual migrations from Alaska and Canada to make the Refuge home for six months. Here they mingle with thousands of other visiting waterfowl, waterbirds, and shorebirds – making the Refuge a true winter phenomenon.

The Refuge also provides important breeding habitat for Swainson’s hawks, tri-colored blackbirds, marsh wrens, mallards, gadwall, cinnamon teal, and burrowing owls. Tri-colored blackbirds, a colonial-nesting songbird, breed in colonies of more than 25,000 pairs in robust herbaceous vegetation. Coyotes, ground squirrels, desert cottontail rabbits, beaver, and long-tailed weasels can also be seen year-round.

Vernal pools are unique and special wetlands found on the Merced NWR. These special pools form when natural shallow depressions underlaid with clay soils fill with winter rainwater. The pools come to life as they fill with water: fairy and tadpole shrimp emerge from cysts embedded in the soils the year before. The endangered tiger salamander, along with other amphibians, lay eggs and rear tadpoles. The vast number of aquatic invertebrates found in these pools provides a food source for wintering and migrating birds as they prepare for the long flight north to their breeding grounds.

As spring arrives and the water in the vernal pools evaporates, wildflowers such as goldfields, purple owl’s clover, and butter-and-eggs germinate in colorful patterns of thick rings or halos around the pool basins. Once the vernal pools have dried out, Downingia and Colusa grass, a rare California species, appear in the parched basins. This annual floral display of color led John Muir to describe the valley floor as the “floweriest part of the world” he had seen.
In addition to managing natural habitats, the Merced NWR contains approximately 300 acres of cultivated corn and winter wheat crops and more than 500 acres of irrigated pasture for wildlife. Not only do these managed agricultural areas provide important sources of carbohydrates for the tens of thousands of arctic-nesting geese and Sandhill cranes that make Merced County their winter home, they also help ensure that the birds will have adequate nutrient stores to make the long migration north to their breeding grounds. Local farmers, under agreements with the Refuge, oversee the ground preparation, seeding, and irrigation of these croplands. The Refuge incorporates a livestock grazing program that works in partnership with local ranchers and farmers. Cattle grazing is a management tool used by the Refuge to provide and maintain short stature grasslands and help control invasive weeds. Grazing also encourages native grasslands and the species that depend on them to thrive.