The possibility that there might be skylarks nesting at Stonehills on the island of Portland, where the famous limestone used to build London comes from, has put a £500,000 project to open a mine on the site on hold.

During an ecological appraisal it was identified that Albion Stone's Stonehills site supported populations of skylark birds. This month (on 3 June), Avalanche Road, which leads to the site, was thoroughly checked for the ground nesting birds and ecologists concluded that even though the survey was conducted within typical bird nesting season, no active nests were found.

However, due to the high levels of breeding activity that usually take place between April-August, Albion Stone has taken the precautionary decision to delay the opening of a mine at Stonehills, which will ensure future supplies of Portland stone from the company.

Albion Stone have appointed Woodmace Ltd Civil Engineering to complete the first phase of the operation to open the Stonehills Mine. The operations were planned to commence with the topsoil stripping in conjunction with the Archaeological Programme of works on Monday 8 June. But Albion suspended the work.

Michael Poultney, Albion Stone’s Managing Director, says: "While it is difficult to suspend such an enormous, well planned operation, we recognise that skylarks, although not rare, have been declining in numbers and the breeding of such bird species needs to be protected.

"Since we took control of the surface [land at Stonehills] nearly 10 years ago, we have worked with Natural England / Dorset County Council ecology teams and the RSPB to enhance biodiversity and the habitat for farmland birds in particular. The management plan has clearly been successful and we are oddly now a victim of that success!"

Joshua Eiles-Clarke of the Woodmace Ltd Operations Department says: "We have carefully planned the operations and were commencing with the final public consultation when the news came through that there was a concern about potential nesting Skylarks on the site.

"Therefore, we are now looking to delay the start date until after the nesting season and will ensure that a suitably trained ecologist gives the site the all clear and we receive confirmation from the planners before the operation commences."