Special bird nesting boxes have been built in memory of a woman who helped crack Hitler's secret codes.

Margaret Bullen, who died at the age of 96 in October, was one of the codebreakers of Bletchley Park.

Workers at the top secret establishment in Milton Keynes deciphered messages used by Hitler and his generals, which helped to shorten the war.

Eastern Daily Press: Nesting boxes are being put up around west Norfolk in memory of Margaret Bullen.Nesting boxes are being put up around west Norfolk in memory of Margaret Bullen. (Image: Archant)

Mrs Bullen's son Andy, a West Norfolk councillor, has had 20 nesting boxes made. They will be put up under the eaves of buildings in Downham Market, Heacham, King's Lynn, Barton Bendish, HIlgay and Methwold.

"Her favourite bird was the swift," said Mr Bullen. "I got in touch with the Forward Day Centre in North Lynn and they made me 20 nesting boxes in memory of my mother."

Mr Bullen, who represents the North Downham Ward, wants the council to require developers to install swift boxes on new properties.

"Urban wildlife is a big thing of mine," he said. "There's all this focus on the eagles, it's a real distraction to the threats facing migrating birds."

Eastern Daily Press: Andy Bullen with Anna Foster from the Swan Project, which is putting two of the boxes on its building on Paradise Road, in Downham MarketAndy Bullen with Anna Foster from the Swan Project, which is putting two of the boxes on its building on Paradise Road, in Downham Market (Image: Rhiannon Eagle)

Swift numbers fell from an estimated 133,600 breeding pairs in 1994 to 52,000 by 2019. The birds spend their entire lives on the wing, feeding, migrating and even sleeping on the wing.

As they make their 8,000-mile flight to Norfolk, conservationists say more must be done to protect one of our most iconic summer birds.

Swifts will soon arrive from Africa after spending the winter in the Congo. One of their favoured nesting sites is under the eaves of buildings.

Eastern Daily Press: A swift peeps out from a nesting boxA swift peeps out from a nesting box (Image: Vanessa Dent)

Mr Bullen, who has set up a swift group on social media which now has more than 4,000 members, believes councils and developers could help reverse the birds' decline.

The Royal Institute for British Architects (RIBA) recommends one new nest place for every new housing unit. Some councils now say the same.

"If this is implemented then we will be a long way down the road to creating the right conditions for a swift recovery," said Mr Bullen. "As swifts rely on buildings for their survival we have a responsibility to help them."