Bewick’s swans may have flown to the rescue of opponents of a concrete factory’s expansion plans at Littleport.

The long-delayed application by McCann to expand their site along the Wisbech Road is facing fresh opposition from the Welney Wetland Centre.

Centre manager Leigh Marshall told East Cambridgeshire Council planners that little attempt has been made to monitor or assess the use of by Bewick’s and Whooper swans in the vicinity.

He said he would have expected the applicants to have “collated much better records on swan-use of Mare Fen fields adjacent to the site”.

Mr Marshall said the information would inform the ornithological survey for describing the birds’ use of the area and the potential impact of disturbance from the concrete plant both during construction and operation.

He would have welcomed suggestions of how disturbances could be minimised to ensure no significant impact on the swans’ use of Mare Fen.

The centre criticised the lack of detailed data in the application.

Bewick’s and Whooper swans have been subject to several counts each winter since the early 1980s, said Mr Marshall, and although the surveys are occasional and not comprehensive they show Bewick’s feeding at Mare Fen within 500m of the site boundary in 1986, 199, 200, 2001, 2003, 2009 and 2010.

“Moreover we understand from local reports and from tracking a small number of Bewick’s the swans have visited Mare Fen more recently, albeit not on our survey dates,” he said.

“This is an important consideration because swans generally show site-fidelity to particular feeding areas, even if there is annual variation in their timing or use of particular fields in line with crop rotation and other factors”.

The wildlife centre also argues that better attention needs to be given to whether noise and human activity – for example movement of tall machinery – would deter them from foraging on nearby farmland.

Mr Leigh said they would like the development plans to be adjusted to ensure “no significant impact” through disturbance to swan-use of the Mare Fen fields.

He said Natural England supported their comments.

Protestors say the plans would see 30 acres of Mare Fen used and what are now green fields “concreted over”.

Save Our Fens protest group said: “The site will also house a factory building 50ft high (higher than St George’s Church) and covering an area of over 33,000 sq ft as well two giant silos 64 ft high (higher than four and a half double decker buses).

“What was a beautiful fen landscape will be an ugly, noisy and dusty industrial site.”