The numerous pothole lakes, sloughs, fresh water marshes, and ponds provide ample aquatic habitat in an otherwise dry environment. The primary value to birds is as a migration staging area in both spring and fall. Dominant species are Northern Pintail, Common Goldeneye, Mallard, and American Wigeon. In most years, more than 1,000 ducks occupy the refuge during breeding season. Dominant breeding species are Mallard, Redhead, Ruddy Duck, and Cinnamon Teal. The wetlands also support breeding populations of Black Terns and Great Blue Herons. The refuge also has high-quality remnants of native sagebrush and perennial grass, and aspen riparian forests. The transition between the shrub-steppe and forest ecosystemscombined with the wetlands, ravines, and basalt outcropsprovides a rich mix of habitats.