White storks could be about to breed in Britain for the first time in almost 600 years.
The storks have started mating rituals, experts say
The birds have started to make a nest in the Calder Valley, West Yorkshire, and appear to be involved in mating rituals, experts say.
The last record of storks breeding in Britain was at St Giles' Cathedral, Edinburgh, in 1416.
An RSPB spokesman said: "Storks usually live in central Europe. It's extremely rare to see them nesting here."
The pair, which were first spotted last weekend, began building their nest on a pole carrying power lines next to the Calder and Hebble Navigation canal near Horbury Bridge.
"Unfortunately they chose a very risky place to do it," said the RSPB spokesman.
"The power lines are off at the moment due to temporary maintenance work, but if they were switched on it would be disastrous."
So the RSPB, in conjunction with Yorkshire Electricity and British Waterways, has erected a replica pylon with a nesting platform next to the original telegraph pole.
"The storks have started collecting sticks for the new nesting site," the spokesman added.
"We needed to act quickly to tempt them there but they seem to be quite happy.
"We're just keeping our fingers crossed that they'll breed successfully."
The new arrivals have caused quite a flap among bird watchers and local residents, with dozens of people flocking to the site to catch a rare glimpse of them.
The RSPB has even set up a temporary facility for visitors, who can use binoculars provided by the society to get a close-up view of the birds.