Numbers may exceed two million by December after the wetland areas of the Klamath Basin and other areas to the north become frozen. Pintails, mallards, wigeon, northern shoveler, snow, Ross's, and white-fronted geese are most commonly seen during these months, but the careful observer can find many others. Waterfowl numbers gradually decline in February and March when they return to their northern breeding grounds. Habitat Diversity Attracts Birds and Other Wildlife Although managed mainly for migratory waterfowl, the refuges are also attractive to other wildlife. The marshes, with readily available fish, frogs, and invertebrates are attractive to grebes, white pelicans, egrets, herons, and bitterns.
Shorebirds probe the mud for seeds, snails, and worms.
Raptors find an abundance of waterfowl, rodents or small birds on which to feed. Woodpeckers, warblers, and other songbirds feed and nest in the cottonwoods and willows bordering the waterways and creeks. Deer and jackrabbits graze in the grasslands and on edges of wetlands. The following list contains 269 species of birds recorded on the refuges since 1937. Wildlife of the Sacramento National Wildlife Refuge Complex.