It is the sort of digger that little boys (of all ages) would dream of sitting at the controls.

And its ability to reach places that other diggers can't reach is being proved this week as it excavates dykes on the Broads Authority's How Hill nature reserve that have been untouched for 100 years.

The seven-ton amphibious digger, which can both plough through mud on its metal rollers or float on water on specially-developed pontoons, is being used for the first time on the Broads as part of an important conservation project.

The Authority's field conservation officer, Rob Andrews, said it had been hired from Surrey-based firm Land and Water to dig out overgrown dykes on the 450-acre reserve near Ludham that could not be reached by conventional machinery.

He said: 'Our aim is to improve the habitat for bitterns by creating more areas of shallow open water in the wet reedbed.'

He said the work was being carried out before the bitterns start booming, heralding the start of their breeding season.

Increasing numbers of bitterns have been seen on the reserve –- including some sightings this winter – as a result of the ongoing conservation efforts, he added.

Three dykes and a pond are being excavated by the digger, which has been employed by the Environment Agency for similar work.

'Last winter we used a different machine which chopped and smashed the reed rather than digging it up, but this appears to be more effective,' said Mr Andrews.

He said the dykes contained very high quality water that was teeming with plant life as well as fish such as eels, roach and bream and aquatic invertebrates including snails, dragonflies and damselflies.

'The abundant fish provide a food source for the bitterns. The habitat is also excellent for other birds such as water rails and ducks which can nest on the edge of the reedbed,' he said.

The work is being carried out in conjunction with Broads Authority-funded fish surveys to determine how fish use the Broadland fens. Mr Andrews said it also fitted in with the aim of maintaining heritage landscapes and restoring old dyke systems.

Mark Cowell, a manager at Land and Water, said the �200,000-plus digger had been developed because his firm had seen the potential for one half the size of existing machines on the market. When transported, its undercarriage is retractable cutting its width from 4.3m to 3.5m

stephen.pullinger@archant.co.uk