Dec 19, 2011

hooded crane hubbub

Birdwatchers at the crane refuge on the Hiwassee River spotted a black crane with a white head among thousands of grey sandhill cranes December 13. Soon it was identified as a hooded crane, an Asian species rarely found in North America. In fact, the Tennessee sighting is only the third known occurrence in the U.S. The second was this spring in Nebraska, and the first the prior spring in Idaho (the bird in the photo).

Hooded cranes have escaped from captivity in the U.S., including a 2006 escape from an Idaho aviary. Three hooded cranes escaped in 2001, also in Idaho. Cranes can live long lives, spanning several decades. If one or more escapee survived, it is likely trying to find a flock and a mate among sandhill cranes it encounters, but it may be having trouble on one or both counts due to its appearance. This could account for the pattern of sightings.

North America has three crane flyways, an eastern route between Florida wintering grounds and breeding grounds near the Great Lakes, a Great Plains route between Texas and the northern plains and tundra, and west-of-the-Rockies flyway between Mexican wintering grounds and northern Alaska. If the Idaho, Nebraska and Tennessee sightings are the same bird, it has switched from the western to central to eastern flyway in the span of four migrations.

In winter, cranes are opportunistic, nomadic, and travel in flocks. On their breeding grounds, they break into pairs or small family groups, and individual birds return to the same nesting area year after year. Unless a crane has no family and no mate, it will be geographically loyal. Unmated birds are subjected to harassment, especially on breeding territory, and an unmated bird that looks different likely gets double trouble. This social pressure could explain how one bird could show up on three migratory routes in close succession.

It does not explain whether the hooded crane originally strayed from a Siberian flock on its own or with human assistance. An initial sighting in Idaho would be expected either way. The retreat of Arctic ice in recent summers has created more opportunities for Siberian flocks to come in contact with Yukon flocks. The wings of a captive bird would be clipped, so it would struggle to fly and keep up with other cranes until molting in a new set of feathers. It should also have leg bands, and the observed bird does not.

Is it the same bird? Is it a wild bird? No one knows for sure.

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