As I was driving home from the YMCA yesterday, I saw two sandhill cranes near a small pond that sits along the highway, only about a half-mile from my house. They were my first sandhill crane sightings of 2014.
But those two birds are also representatives of one of the Earth’s Great Migrations — a natural phenomenon we usually only associate with the African continent. We often forget that at the end of March, one of the planet’s most extraordinary migrations takes place right here in the United States. Five hundred thousand sandhill cranes head to Nebraska, to a site along the central Platte River. Unfortunately, the area of convergence has shrunk to a strip of land only about eighty miles long.
If rapid climate change, increasing human population pressure, and invasive species continue to influence this tiny plot, will our cranes be able to adapt, or will we, in our lifetimes, lose yet another natural wonder?
Eighty miles on the brink of extinction
Among the world’s oldest living birds, cranes have been around since the Eocene, which ended thirty-four million years ago. They are one of the world’s most successful life forms, outlasting millions of species (99 percent of the species that have ever existed are now extinct). The particularly successful sandhill crane of North America — the most abundant crane species — has not changed appreciably in ten million years.
Not only have sandhill cranes been around for quite some time, their migration has a long history. According to the fossil record, it’s been going on for millions of years.
Today, the Platte River Valley is the most important stopover on the sandhills’ long migration north from places such as Arizona, New Mexico, Oklahoma, Texas, or Mexico. The region is so vital to birds that it has been designated an Important Bird Area of Global Significance. Every year, four hundred thousand to six hundred thousand sandhill cranes — 80 percent of all the cranes on the planet — congregate along an eighty-mile stretch of the river, to fatten up in preparation for the journey to their Arctic and subarctic nesting grounds. This staging takes place in three waves of four to five weeks each, beginning in mid-February and ending in mid-April — peaking in the last week of March — during which birds that arrive emaciated from wintering grounds gain 20 percent of their body weight.
But whether the cranes will survive our rapidly changing climate and land development remains to be seen. Some say the Platte is almost dead and that the whole environment has been manipulated beyond restoration. The river has lost 80 percent of its width and 70 percent of its flow to hundreds of diversions — including eight major dams on the North Platte and twenty on the South Platte — that siphon it off for municipal and agricultural use. Fifty miles of crane staging habitat have been lost to dams and “reclamation”; only the eighty miles from Overton to Chapman remain.
Invasive wetland plant species, such as common reed and purple loosestrife, have also made negative impacts on the Platte River. In recent years, they have been encroaching on riverbanks and anchoring sandbars on the central Platte River, causing drastic changes in the river’s hydrology and surrounding habitats. When common reed and purple loosestrife start to invade, plant diversity is reduced until an eventual monoculture exists. The number of bird species found in invaded riparian areas and wetlands decrease due to the limited plant diversity and alteration of the river’s natural processes.
In addition, rapid climate change is melting the glaciers in the Rockies where the Platte rises. In 2012, the tornado season arrived three months early; in March there was a cluster of monster tornadoes only a hundred miles west of the staging. In l990, a flock of sandhill cranes was killed by a twister.
A bird that has stood the test of time
Others believe, however, that despite us, the sandhill crane staging on the Platte will continue long into the future. Sandhill cranes are highly adaptable — they wouldn’t have lasted for millennia if they weren’t. As the Platte changes, so will the birds’ habits. After all, sandhill crane population numbers have been stable for the last ten to fifteen years.
Many Native American nations had Crane Clans, including those in my home state of Wisconsin. To the Menominee, the Crane is a guardian bird, keeper of knowledge and science.
Perhaps we could learn to be better guardians from the cranes—especially when it comes to protecting that tiny strip of land that they depend on.
Do you think common birds, such as sandhill cranes, will feel the effects of climate change? Or are such adaptable species well equipped for the future?
Here’s to finding your true places and natural habitats,