A conservation team based in the Wensum Valley is encouraging members of the public to help gauge the success of a breed and release programme by listening out for a distinct bird cry.

Corncrakes have one of the bird world’s most distinctive cries and by keeping a record of the numbers of detected birds, the conservation team at Pensthorpe Natural Park, near Fakenham, are hoping to track how many have survived the winter and migration.

Each year they make an 8,000-mile migratory round trip to the Democratic Republic of Congo, where they spend the winter and then return to the UK at the end of April and into May.

They were once widespread across the UK but have been in decline and numbers have now reached their lowest point since 2003. The reason for the fall in numbers is due to numerous factors, including habitat destruction on the wintering grounds, hunting on migration routes and changes in agricultural schemes.

To combat this the Pensthorpe Conservation Trust, which is based at Pensthorpe Natural Park, has spearheaded a breed and release programme and last year 154 corncrakes were hatched and reared by the team.

The birds were released from a location within the Wensum Valley in the summer of 2017 and it is hoped that 15 to 20pc of them will return to the area in spring, ready for the breeding season.

Pensthorpe’s head of species management, Chrissie Kelley, said: “These fascinating, rare, farmland birds are seriously under threat so we are appealing for help from local birding groups and the general public to listen out for the distinct rasping cry of the corncrake.

“We can only start to understand the success of our efforts by determining the numbers of returning birds. Of the 69 birds we released in 2016, four males were known to have returned, but we suspect numbers were higher. We hope by engaging support we will gain a clear understanding of return success.”

Generally, corncrakes prefer grassland including wet and dry meadows, and tall crops. They also live at close quarters to humans.

Anyone who hears the distinct ‘crex crex’ call are asked to email Pensthorpe or post @wensummonitors on Twitter using the hashtag #corncrake. For more information visit their website.