Bitterns were nicknamed bog boomers centuries ago because of their legendary call, like a lowing cow or distant foghorn.

The distinctive sound of one of Britain's rarest birds is so loud it can be heard up to two miles away.

Bitterns are sometimes heard booming among the reedbeds of the Combe Haven valley, a lost world hidden behind seaside resorts of Bexhill and Hastings.

But their calls could soon have to compete with the roar of traffic speeding between the two towns on a link road that will cross or skirt their marshy home.

Councils began consulting on the road this week, a smaller scale alternative to the larger Hastings and Bexhill bypasses rejected three years ago.

Six routes are being considered, each a little more than three miles long and most relying on embankments or viaducts to carry them above the valley.

Without the road, Combe Haven is silent. Clumps of ancient woodland and meadows ring the valley's marshy bottom, which glows golden yellow in the winter sunshine.

There is little to remind visitors the valley lies so close to settlements with a combined population of 130,000.

The next-door towns do not deter visiting bitterns, nor the marsh harriers, swallows and warblers that have turned Combe Haven into a crucial stop-off point for migrating birds.

Otters, hunted close to extinction in the Fifties, have even returned to the valley in recent years, helped by its designation as a site of special scientific interes and wildlife-friendly management.

The Hastings Alliance, which successfully fought the bypasses, argues the link road would be no better than the bypasses.

Campaigners eye suspiciously Rother District Council planning guidelines that used to say Combe Haven's landscape was equal to the best of the nearby High Weald area of outstanding natural beauty.

The sentence has been dropped from the most recent version of the document.

Derrick Coffee, of East Sussex Transport 2000, said: "In landscape terms it will totally change the character of what is an unspoilt and tranquil place.

"It is a precious environment and anybody expecting a link road to be built without a protest is greatly mistaken."

He said the bypasses had been rejected for economic and social reasons, as well as concerns about the environmental consequences.

Most road journeys between Bexhill and Hastings are local.

The school run accounts for about 30 per cent of traffic during the morning rush-hour, well above the national average.

Seventy per cent of proposed development would have been possible without the western bypass, a figure that still stands for the link road.

Worryingly for traders in Bexhill and Hastings, the road could make it easier for shoppers to head for Tunbridge Wells or Bluewater instead of nearer town centres.

Mr Coffee said alternatives such as walking, cycling and public transport needed to be examined before local authorities, including East Sussex County Council, Hastings Borough Council and Rother District Council, embarked on road building.

He said: "These people start with the car but they have still not taken on board that if you build roads, they fill up with cars.

"They are actually making it harder and harder to make progress with schemes that will help walking and cycling because traffic levels put people off.

"If you persuade people to get rid of the second car you increase the market for public transport, not just walking and cycling."

The county council's attempts at developing integrated transport were criticised recently after the Department for Transport penalised it for poor performance.

Money was held back after regional planners said too many integrated transport schemes were "still going through consultation with few outcomes".

However, a council spokesman said yesterday two-thirds of projects were being completed, which was above the national average, and it had been penalised for making changes to individual schemes following consultation.

Mr Coffee said: "The leadership is far too focused on big schemes such as the Bexhill to Hastings link road while setting aside smaller schemes.

"If they do go ahead with the big road approach every alternative would be shackled.

This road would confirm the car habit and we have enough boy racers thank you very much."