The Snake River provides habitat for migrating waterfowl, riparian vegetation, and fish species. Mild Hagerman weather, in combination with spring water flowing at a constant 58 degrees Fahrenheit (14.4 degrees Celsius), allows much of the water to remain ice free during the winter months, attracting thousands of birds.
In recent winters, wildlife biologists have counted as many as 55,000 ducks and 4,000 Canada geese in the area. Mallards, gadwalls, redheads, ruddy ducks, and Canada geese commonly nest and raise young in the area. Other migratory waterfowl that can be found include tundra and trumpeter swans, northern pintails, American wigeon, cinnamon and green-winged teal, lesser scaup, and ring-necked ducks.
A variety of wading and shorebirds nest at Hagerman, while others stop briefly before continuing their northward migration. The short-eared owl and the western screech owl commonly nest in Hagerman. The ring-necked pheasant, grey partridge, and California quail also call Hagerman home. Black-crowned night herons, great blue herons, Virginia rails, American avocets, and spotted sandpipers are some of the species that stop briefly. Ospreys, bald eagles, peregrine falcons, and rough-legged hawks are seasonal guests. Marsh wrens, rufous-sided towhees, and numerous warblers species find sanctuary within the riparian areas, while horned larks, vesper sparrows, and northern orioles feed and nest among upland and wooded habitats.
The peregrine falcon (Falco peregrinus anatum) and the bald eagle (Haliaeetus) are federally listed threatened species and may be periodically seen on the Monument, but are not residents.