Mystery surrounds the disappearence of rare wader chicks at a Norfolk wetland reserve.

Nature lovers mounted a vigil at the Welney Wetland Centre in the Fens after a pair of black-winged stilts nested on the site for the first time. They feared that egg thieves would target the nest.

Twenty-five people took part in stilt watches around the clock for 10 days.

When the brood hatched, the Wildfowl and Wetland Trust went public, saying the birds' breeding was an inspiring conservation story.

Today it emerged that the nest had failed. Earlier, bird watchers said they believed that the young had disappeared.

Mark Simpson from the Wildfowl and Wetland Trust said: 'It appears that the stilt pair has lost its chicks.

'The adults were seen to move to the far side of the reserve, indicating that they no longer had the chicks with them. They are currently back where the chicks were last seen.

'Staff and volunteers at Welney have not yet been able to confirm exactly what has happened, but we fear the worst.'

There is speculation that the chicks could have been killed by a predator such as a stoat or bird of prey. Sparrowhawks and peregrine falcons are common in the Fens.

The birds had built their nest on an area of land called Lady Fen, which has been fenced to keep out larger predators such as mink and otters.

'It seems likely it could have been some kind of predator,' said Mr Simpson. 'It's sadly one of those things that affects all wildlife.

'We were excited that the stilts managed to raise their chicks at Welney. We just hope they come back next year.'

Stilts are classed as vagrants - rare visitors - to the UK by ornithologists.

Normally breeding around the Mediterranean, they can be driven north when conditions are drier than normal in their usual habitat.

A pair successfully bred at Holme, near Hunstanton, in 1987 and at Cliff Marsh, in Kent, in 2014. Experts say that climate change may bring them to our shores more regularly in future.

The birds are easily distinguished from native waders with their black and white plumage, thin black bill and long, spindly red legs.