A Norfolk natural park is seeking to boost the numbers of a threatened species of bird.

Pensthorpe Natural Park, near Fakenham, has installed two nest boxes playing frequent and repeated swift calls in the hope of attracting the amber-listed species to the reserve.

Swift numbers are reported to have been reduced by half between 1995 and 2015, with the new boxes set to project out the noises intermittently through a speaker to attract the species which migrates to the UK to breed from May to September.

Richard Spowage, reserve manager at Pensthorpe, came up with the idea of installing the boxes and said: "Adding swift call sounds could make all the difference to our biodiversity.

"We hope that this year the swifts will be drawn in by the noise, but we don't yet expect them to breed.

"Instead we hope that they will return next year as they become aware of Pensthorpe offering a suitable breeding ground."