A pair of squatters have brought a multi-million pound construction project in Manchester to a halt.
It is hoped the falcons will raise a brood of chicks
Restoration work on City Tower, one of the city's tallest buildings, was stopped after two peregrine falcons moved into the top floor.
Peregrine falcons are very rare in city centres but are sometimes spotted, usually only one at a time.
It is extremely unusual for a mating pair to set up home in such an urban environment, the RSPB said.
'Jack and Vera'
Bruntwood, the owners of the building, stopped external work on the tower at Piccadilly Gardens to allow the birds to breed.
It has employed an architect to design a permanent breeding site for the birds to breed in the future. The company is also in the process of installing a tiny camera close to the nest to observe their breeding habits.
It is hoped that Jack and Vera, as the birds have been nicknamed after the Coronation Street characters, will eventually nest and lay eggs.
Single peregrine falcons are believed to have used the building on and off for the last 10 years but in February workers spotted two of the birds flying around.
'A little excited'
A spokesman for the company said staff are "more than a little excited about this".
"All the staff are fascinated, especially in the mornings when the falcons are most active," he added.
Margaret Overend, of RSPB North West, said: "This is a great thing to see. These birds naturally use things like cliff faces to breed but it sounds like they have found an urban alternative.
"Anyone who has seen a peregrine will understand why this is such a special event. They are wonderful birds to watch."