There is a large rookery at this end of the village. The noise of them nesting I can (just about) cope with, but they raid the bird feeders. They cannot perch on the seed feeders, but they try, flap wildly and do their best to break them. Or at least to tip seed onto the ground.
I daren't put anything out for the ground feeding birds, since a swarm of rooks/crows (a veritable "murder" of the wretched things) will swoop down and take everything.
They deter the smaller birds, and with the yearly growth of the ever-increasing rookery, the numbers of smaller songbirds have diminished.