Wildlife & Habitat


Bill Williams River National Wildlife Refuge holds one of the last stands of naturally regenerated cottonwood-willow forests along the lower Colorado River.

Situated in a transition zone between Mojave and Sonoran desert, this unique ecosystem provides excellent habitat for many resident and migratory wildlife, including 355 species of birds, 34 documented reptiles, 40 species of butterflies and 57 species of mammals and 7 amphibians.

Because the refuge contains the largest remaining stand of native cottonwood and willow forests on the lower Colorado River, it draws a variety of Neotropical migratory birds from Central and South America migrating to their breeding grounds. Yellow warblers, vermillion flycatchers, summer tanagers and other bright colored birds can be seen along the riverbed or perched overhead in the tall trees. The refuge is host to some endangered birds as well, including the southwestern willow flycatcher, which nests on the refuge, and the Yuma ridgeway's rail, which resides in the marsh’s cattails but is most likely heard at dusk and dawn with their dry kek-kek-kek.

The surrounding desert uplands and the refuge’s rugged cliffs are home to a diversity of wildlife, including majestic desert bighorn sheep, mule deer and an occasional mountain lion. On the landscape, rattlesnakes recede into the coolness of a crevice and desert tortoise feed on prickly pear cactus. The western viceroy butterfly and Macneill sooty wing skipper find one of their last strongholds along the lower Colorado on the Bill Williams River. The river also supports a diversity of non-native sportfish, including largemouth bass and channel catfish. The refuge has documented 192 aquatic species that live some or all of their lives within the river, including 23 species of dragonflies.

It is the diversity of habitats found on the Bill Williams River National Wildlife Refuge that sustains one of the highest diversity of wildlife and plant species within the lower Colorado River watershed. It has been recognized by the National Audubon Society and The American Bird Conservancy as a birding area of global importance.