A portion of three distinct populations of sandhill cranes winter in Arizona. Cranes from both the Rocky Mountain (RM) and mid-Continent (M-C) populations winter in the Sulphur Springs and Gila River valleys of southeastern Arizona. Sandhills from the Lower Colorado River Valley (LCRV) population winter along the lower Colorado River, primarily on the Colorado River Indian Reservation and Cibola National Wildlife Refuge, and below Gillespie dam on the Gila River. RM cranes nest primarily in Idaho, Montana, Wyoming, and Utah. LCRV cranes nest primarily in northeastern Nevada. The nesting range of the M-C encompasses most of Canada and Alaska. The M-C population migrates through the central plains, staging on the Platte River both spring and fall, to wintering grounds in Texas, Oklahoma, New Mexico, Arizona, and Mexico.
Wintering areas selected by sandhills feature shallow water roosting areas with low or no vegetation; playa lakes and sandbars along shallow/braided rivers are preferred. Cranes winter in close proximity to harvested grain fields, corn is preferred. In mid to late February cranes begin their return migration to nesting areas.
Cranes leave roosting areas in early morning, usually about sunrise, to fly to feeding areas, where they spend three to four hours. During midday the cranes return to the roost, or go to nearby loafing areas, which can be grasslands or wetlands. In the late afternoon cranes sometimes make short visits to feeding areas before returning to the roosts.
Sandhill cranes in the western United States nest in high elevation shallow marshes and wet meadows. Sandhills do not nest until they are four to five years old and typically have very poor success the first couple of years. Typically, cranes lay two eggs, but only about 1/3 of the successful nesters are able to raise two young. In dry years, when wetlands shrink, predators, especially coyotes, take a heavy toll on the flightless young. During recent dry years the proportion of young-of-the-year birds in the fall population has been around 4 percent. Even in good production years young-of-the-year birds rarely comprise more than 12 percent of the fall population.
Depending on habitat conditions sandhills begin to congregate in local agricultural areas, called pre-migration staging areas, in late August. Migration to wintering areas begins in September. Cranes typically migrate in a few long, high altitude flights stopping at traditional stopover areas. For cranes of the three populations that winter in Arizona the major stopovers are the Platte River in Nebraska for the M-C, San Luis Valley in Colorado for the RM, and wetlands near Lund, Nevada for the LCRV. Cranes begin arriving on wintering areas in late September.