The 4,507-acre (18.24 km2) refuge primarily consists of intensively managed wetland impoundments, with some grassland and riparian habitats.

Colusa National Wildlife Refuge typically supports wintering populations of more than 200,000 ducks and 50,000 geese.

The refuge is a stronghold for populations of the endangered palmate-bracted bird's beak and the threatened giant garter snake.

About 35,000 visitors come to the refuge each year for wildlife viewing and 4,000 come to hunt waterfowl and pheasant.

This article incorporates public domain material from websites or documents of the United States Fish and Wildlife Service.