its Autumn and birds are in my loft

Help please.

We have had birds nesting in between 2 floors and it has been particularly bad as we have seen bird might infestation. I waited for the birds to leave the nest and lifted the floor and removed several redundant nests. The plan was to erect a bird box outside and to repair the loft entry point this autumn (in the next few weeks) but it sounds as if the birds have returned or others taken up residency. Can this really be the case, its autumn?