While some species will habitually return to established sites like roof spaces, there is (unfortunately) nothing in law that protects those spaces or the nests in them when they are not occupied. The RSPB states that “If you must deter birds from nesting in your roof, work to deny access must be done during the winter months when they are not nesting”.(Note: pigeons can nest throughout the year).
They go on to say that “You should always avoid roofing work if you know birds are nesting there, but sometimes a roof nest is only discovered during renovation work. If this happens and the roof cannot be left until the young have flown, you can make an artificial nest box quickly and simply by cutting a four-litre ice cream tub.”
Many bird habitats (so the places where they nest rather than the nests themselves) are protected though and local planning authorities (LPAs) have a duty to conserve their biodiversity.