PEREGRINE falcons are believed to be nesting in Hadlow Tower – and could delay work to preserve the Grade I listed monument.
The tower, which dates back to the 1800s, is due to undergo a £4million restoration after a compulsory purchase order is put into action.
But the relatively scarce breeding birds, which are believed to be nesting at the top of the tower, have special protection – making it an offence to disturb their nests.
Sonny Stoneley, who initially recognised that the falcons were in the tower, said he had heard them in the mornings and they had been seen flying across the castle grounds.
"They are eating all the pigeons in the grounds, which I think the people living there are happy about," he said.
Michael Kiesser, who currently owns the tower, said: "I hear them every day as they have a very distinctive screeching noise. Neighbours and villagers have been coming to have a look at them."
The compulsory purchase order, which was approved in March last year, means the borough council will take possession of the tower before passing it to The Vivat Trust.
The trust is planning to refurbish the tower to include short-term holiday accommodation, with a separate exhibition centre planned for part of the ground floor.
Steve Gilbert, from the RSPB, said peregrine falcons have more commonly been seen across the south-east in recent years nesting in tall buildings.
He added: "The birds are not extremely unusual but are something to be noted. They are among the fastest birds around when they swoop, and they have special protection under Schedule One of the Wildlife and Countryside Act."
The act states that it is an offence to take, injure or kill a peregrine or to take, damage or destroy its nest, eggs or young – with a fine of up to £5,000 and a prison sentence of up to six months.
Mr Kiesser said he was not hoping the work would be delayed but had heard from people that the nests could not be disturbed.
A spokesman for the Vivat Trust said the building would be starting as soon as possible but there was no definite time frame.
She said: "It is not unusual for wildlife to use derelict buildings and we are well aware of the restrictions and working with the wildlife.
"It is not a case of the wildlife stopping the building, it is just that it needs to be taken into consideration."