Pigeon racers say scores of their birds are mysteriously vanishing in what some claim is Britain's bird equivalent of the Bermuda Triangle.
Fanciers say they are experiencing "disastrous" and unprecedented losses in an area between North Yorkshire and Country Durham.
In one recent event, only 13 of the 232 birds released in the region made it home to Scotland.
And 200 failed to show up after 1,000 were released over the Triangle, which spans from Wetherby near Leeds to Consett, Co Durham.
Keith Simpson, of the East Cleveland Federation of pigeon fanciers, said: "They're calling it the Bermuda Triangle but who knows where they are going?
"Last weekend a mate had 63 birds away from Durham and 25 went missing.
"It's heartbreaking, it's puzzling and some people's seasons are finished because of this."
He said his club also got reports of 24 dead birds on a North Sea oil rig 40 miles off the Yorkshire coast.
Mr Simpson added that it was impossible to say why flocks were going AWOL, but it could be down to freak weather patterns in the area or a mystery illness.
Pigeon fancier Gordon Braban, secretary of the Washington Celtic Homing Society in Tyne and Wear, said he races some of his birds from the south of France to Newcastle, so losses are not uncommon.
But he said he was "gutted" at the number that have failed to return to the loft this year.
In a recent club race from Wetherby to Newcastle, a route that crosses the "Triangle", he released 1,014 birds and lost around 200 - an unprecedented amount, he said.
"There are people all over England losing vast amounts of pigeons," he added. "We've all been taking big hits over the last few months.
"A lot of owners have been finishing races 20 or 30 short. Where do they go and how do you lose that many? I can't put my finger on it."
He said an increase in satellite activity during the Olympic Games could have scrambled the birds' natural homing device, or it may be down to the bad weather Britain has experienced this summer.
Racing pigeons can be identified by a tag on their leg and racing clubs often organise couriers to pick up lost birds and return them to their owners.
Details of how members of the public can report a lost homing pigeon can be found at www.homingpigeons.co.uk.