Lone whooper swan last hope for millions

The hopes of millions of people around the world who have followed the progress of six swans on their winter migration from Siberia to Britain are resting with a single bird ­ Huck the whooper.

Scientists from the Wildfowl and Wetlands Trust (WWT) have been monitoring the swans by using radio transmitters the size of cigarette packets strapped to the birds' backs and tracked via satellite. The result has been a worldwide audience that has charted the swans' movement south this month, via the internet, television, radio and newspapers.

But the blips on the screen have gone out one by one, and the experiment's authors are trying to work out whether the birds are the victim of failing technology or have fallen foul of the hunter's gun or other predators. Dr Eileen Rees, the head of the waterbird population research unit at the WWT, said: "I was so disappointed, because we particularly wanted to know the flying routes they use to get from Europe to Britain." None of the paths has been completed; Huck is still in Finland.

The project, which the WWTis sponsoring with the BBC Natural History Unit, sounded straightforward. But problems started as soon as the migration got under way on 3 November. One transmitter, attached to a Bewick's swan named Alexei, never seemed to work. Others petered out, or worked sporadically. Yesterday there was only one working reliably, attached to Huck. "We have had problems with tracking several of the birds," a WWT spokesperson said with admirable restraint.

The biggest fear is that the missing swans have been shot by hunters or eaten by an animal. After a similar experiment in the 1990s, when the tracking devices worked rather better, scientists tracked one transmitter, and its swan, to an Inuit's fridge and another to an Arctic fox's lair.

The transmitters, made by an American company, Microwave Telemetry, cost about $2,000 (£1,200)each and weigh 45 grams (2oz), compared to the 100g of the 1990s versions. The company suggested the problems could be due to the birds shrugging off the harnesses, or misaligning the aerial.

The monitoring is intended to discover where in their migration the different breeds stop off ­ known as "staging". "They fly along the Baltic coast, where there are 61,000 lakes and only six scientists," Dr Rees said. "We didn't have any idea where the whoopers stop off. Having pinpointed the key migratory sites, you can advocate protection of those areas".