|
|
Sandhill spectacle
A trip to the Platte this spring might be your most thrilling ever
Contributed by Eldon Greij
Published: October 22, 2010 A biologist picked me up in the dead of night one March for a once-in-a-lifetime birding adventure.
We drove through the pitch black to an area near the Platte River in east-central Nebraska and quietly walked to a hidden blind. As we went, I could hear the soft, scattered calls of resting Sandhill Cranes coming from all directions.
Soon shapes appeared in the pre-dawn light, and the density of birds became apparent. As sunrise approached, small groups raised their voices and lifted off, followed by larger groups of 20 or 50. The bugled, rattling calls were incredibly loud. The groups contained clusters of two to three birds, which likely were paired adults or family units.
Then it happened: Tens of thousands of cranes lifted off together. The swirling masses of cranes were spectacular and, at the same time, a bit unreal. The sound was deafening. Roger Tory Peterson once told me that all birdwatchers should experience the cranes on the Platte. I couldn’t agree more.
The Platte in Nebraska is a major staging site for Sandhills. About 500,000 stop over between late February and mid-April each year, and most are there at the same time. (The numbers were determined by means of nighttime infrared photography from 2001 to 2005.) Members of the Aransas-Wood Buffalo population of Whooping Cranes also stop over along the river, adding to the fun.
Both the Crane Trust (formerly the Platte River Whooping Crane Maintenance Trust) and the National Audubon Society’s Lillian Annette Rowe Bird Sanctuary own land on the Platte and provide access for birders. Peak observation time for Sandhills is from about the third week of March to the first few days in April.
|
Annual Midwest Crane Count
Help the International Crane Foundation monitor the abundance and distribution of cranes in the Upper Midwest. Count cranes with more than 3,000 other volunteers on April 16, 2011, 5:30 a.m.-7:30 p.m.
Contact: www.cranecount.org
|
A mile wide, an inch deep
The old saying that the Platte is “a mile wide and an inch deep” may be a bit inflated, but the river is indeed shallow and has many sand bars and islands, both submerged and exposed. The area allows cranes to roost surrounded by a protective barrier of water, while the open canopy affords no cover to predators above. Cranes typically sleep while standing, often on one leg.
Good water flow is important, because it scours the river bottom, removing woody vegetation, such as willow, before it can become established. Since diversion of water upstream leads to decreased water flow downstream, allowing islands and sand bars to become dry and vegetation to grow, irrigation presents a potential problem.
During the day, cranes forage in corn fields, where they eat kernels left from harvest, and in old fields and meadows, where they feed on invertebrates, especially earthworms and beetle larvae. Corn from area farmers has been an important food source since the 1940s. Cleaner harvest techniques, however, are resulting in fewer kernels left on the ground and may lead to a need for special management programs in the future.
At about sunset, the cranes return to their roosts. The birds come in high over the river and drop down vertically. Holding their wings open and dangling their legs, they resemble humans hanging from parachutes. Before hitting the water, the cranes flap their wings expertly to slow their fall.
Most of the cranes that stage on the Platte, individuals of the Lesser, Canadian, and Greater subspecies (see sidebar below), move north to breeding grounds in parts of Canada and Alaska, but some travel even farther, to northern Russia. Gary Krapu, a research wildlife biologist with the USGS Northern Prairie Wildlife Research Center, placed satellite transmitters on 133 cranes that had been captured at the Platte between 1998 and 2003. Of those, 35 continued across the Bering Strait to Siberia.
Sandhills have been expanding in northeastern Siberia during the last 50 years and currently number about 140,000. Some nest as far as 1,600 miles inland from the strait. In the fall, the cranes retrace their flight pattern and spend the winter in southern parts of North America.
The birds pair for life. Courtship involves frequent vocalizations — synchronized duets that pairs perform while standing close together, their necks erect — and elaborate dances featuring pronounced jumping.
Sandhills typically lay two eggs two days apart. Incubation begins with the laying of the first egg, lasts about a month, and is carried out by both sexes. The first chick hatches earlier than the second and appears to be stronger. Only 12 percent of the mid-continent cranes have two young, according to Krapu. Predation is probably the reason for the low number.
Take advantage of these fascinating birds, and try to see them sometime during the year. (Subscribers can read a list of crane-viewing locations on BirdersWorld.com; see “On the Move,” February 2008.) If you can make it to the Platte, you won’t be disappointed. The spectacle of crane watching reveals how amazing these birds can be.
|
Six Sandhill subspecies
Currently, six subspecies of Sandhill Cranes (Grus canadensis) are recognized on morphological data. DNA evidence, however, shows only two forms -- the Lesser and all the others. All of the migratory subspecies pass through Nebraska.
1 Lesser (G. c. canadensis)
The smallest Sandhill. Winters primarily in eastern New Mexico, northwestern Texas, and northern Mexico but also in California’s Central Valley. Breeds in Alaska and northern Canada, including Arctic islands. Makes up most of the Sandhills staging along the Platte.
2 Greater (G. c. tabida)
The largest subspecies. Winters along Texas Gulf coast, in the Rio Grande Valley in New Mexico, and in Arizona, north-central Mexico, and California’s Central and Imperial Valleys. Breeds in central and southern Canada and parts of the northern United States (east and west). Composes about 5 percent of the cranes staging along the Platte River.
3 Canadian (G. c. rowani)
Intermediate in size between the Lesser and Greater. Winters mainly in coastal Texas. Breeds in central Canada. Makes up about 15 percent of the cranes along the Platte.
4 Mississippi (G. c. pulla)
Nonmigratory, endangered. Found on and adjacent to Mississippi Sandhill Crane National Wildlife Refuge.
5 Florida (G. c. pratensis)
Nonmigratory. Occurs in Florida from the Everglades north to southern Georgia.
6 Cuban (G. c. nesiotes)
Nonmigratory, endangered. Occurs on Cuba and the Isle of Pines.
|
|
See great photos of birds, get birdwatching tips, learn about birding events, and more!
|