Most Police Authorities have a Wildlife Crime Liaison Officer or even a whole squad or similar.
The mud nests under the eaves of houses will belong to house martins, not swifts which are more likely to nest under the roof tiles, but it is illegal to destroy martin or any other nests.
Posts
thank you everyone, who is the ideal people to complain to...?the council, police or rspca, or all three!
This is what Dove says up-thread-the RSPCA are sometimes slow to act -perhaps all three is the way to go