Late in February, while the San Luis Valley is still frozen hard at night, the first cranes come in from the south. Within weeks there are thousands of them in the stubble fields and shallow marshes around Monte Vista, gray birds four feet tall with red crowns, dancing, feeding and filling the air at dawn and dusk with a rolling, rattling call that carries for miles.
One population, one valley
These are greater sandhill cranes of what biologists call the Rocky Mountain population, about twenty thousand birds, more in some years. They winter along the Rio Grande in New Mexico, around Bosque del Apache National Wildlife Refuge, and in Mexico. They nest in the wet meadows of the northern Rockies, many of them at Grays Lake in southeastern Idaho and around the Greater Yellowstone country. Between the two lies a long stretch of dry mountains and desert, and the San Luis Valley, high, flat and laced with irrigation water from the Rio Grande, is where nearly all of them stop to rest and fatten.
They stay from February into late March, then go north. In the fall they come back through, from late September into November, with the year's young birds, called colts, flying beside their parents. A colt stays with its family through its first winter and leaves only when the next spring's migration begins.
A refuge farmed for birds
The Monte Vista National Wildlife Refuge was established in 1953, mainly for waterfowl, and became the cranes' main stopping place. Refuge staff grow barley for them and manage the wetlands where they roost standing in shallow water, safe from coyotes. The birds also feed in the valley's private fields, gleaning grain left after harvest, and gather at the Alamosa refuge and the state's wildlife areas nearby.
The Monte Vista Crane Festival has celebrated the spring return since 1984, with bus tours of the refuge at dawn and thousands of visitors who come mostly from Colorado and New Mexico.
The whooping cranes
For a time a few much rarer birds flew with them. From the mid-1970s into the 1980s, trying to establish a second wild flock of endangered whooping cranes, biologists placed whooping crane eggs in sandhill nests at Grays Lake, hoping the foster parents would raise the chicks and teach them this same migration. The sandhills did raise them, and the young whoopers learned the route through the San Luis Valley. But they never paired with their own kind, and the flock died out. For years festival-goers looked for the last few tall white birds among the gray ones. They are gone now, and the cranes that come through each spring are sandhills alone.