A UNIQUE solution for the conservation of the greatly-endangered whooping crane (Grus americana) is currently under trial in the us. Kent Clegg, a biologist and rancher, belonging to south-eastern Idaho hit upon the idea of teaching cranes to migrate to areas where their lot would not be threatened, by following an ultralight aircraft (ul). The north-western territories of Canada, home to the only self-sustaining population of whooping crane in winter, borders the Gulf Intracoastal Waterway, one of the busiest in the world. Much of the cargo passing through the area contains petroleum products and an accidental spill could push the birds to the brink.

Clegg's research, funded by the us Fish and Wildlife Service, Windway Capital Corporation of Wisconsin, the World Wildlife Fund-Canada and the National Biological Service used captive-reared sandhill cranes (Grus canadensis tabida) as research substitutes for the rare whoopers. Under natural conditions, juvenile cranes learn a migration route and winter location from their parents. But in this case, the creation of new migratory populations and destinations could be done only with captive-reared juveniles. The objectives of the experiment were to determine whether young captive-reared sandhill cranes could be trained to follow an ul to a specific wintering area; cranes reared in a semi-wild environment could develop behaviour typical to the wild; and whether these birds would return unassisted to their summering areas. Initially, Clegg led them behind an all-terrain vehicle or truck. The actual experiment took off last year when he took 11 sandhill cranes on a 1,204-km migration route from Idaho to the Bosque del Apache National Wildlife Refuge in New Mexico.

The selection of landing spots on the route depended on when the birds became tired, night approached, the uls needed fuel, weather became unfavourable or the cranes scattered due to golden eagle attacks. A second and faster ul accompanied the party to monitor conditions in advance, select the landing sites and protect the cranes from the eagles. Daily distances flown varied from 43 to 217 km, depending on factors like wind, temperature, snow, terrain and daylight. But, by the time the group had settled down at the Reserve, in the company of the wild cranes, their numbers suffered considerably due to eagle, coyote and poaching attacks. In fact, one had even returned to the Clegg ranch, early on in the trip.

But the remaining four cranes did spend the summer associating with their wild cousins, feeding in the uplands during the day and roosting in the wetlands at night. And at the end of the season, they too took flight like the wild ones. While two of them dispersed, the other two returned on their own to their summer homes. Although the crane losses have been disappointing, a more fine-tuned version of the technique has the potential for establishing migratory flocks of captive-reared cranes. Research is currently continuing with sandhill cranes and if the results are favourable, a small batch of whooping cranes are likely to be trained in 1997.