Colusa National Wildlife Refuge is a protected wetland in the Sacramento Valley of north-central California and part of the Sacramento National Wildlife Refuge Complex. Spanning 4,507 acres, it consists mainly of intensively managed wetland impoundments, with smaller areas of grassland and riparian habitat. These habitats support huge winter concentrations of waterfowl, including more than 200,000 ducks and 50,000 geese, while also serving resident wildlife and migratory birds in spring and summer. The refuge's grasslands sustain endangered and sensitive plants, and it is an important stronghold for the endangered palmate-bracted bird's beak and the threatened giant garter snake. It also draws many visitors for wildlife viewing and hunting.