Rooks and Pigeons

I have a suggestion aswell. For seeds I used to have a similar situation the big bird would prevent the smaller bird from getting them but I found a solution that worked. I only had one feeder so if the big bird had it and the other smaller birds couldn’t get it. but I tryed an idea I put another feeder out or a couple of them depending on if there only one big bird or more than one and put this one further away from the previous feeder so the big bird doesn’t feel like the small birds are in his space. And then if the small  birds find they can’t get to the previous feeder cause of the big bird they will settle for the other feeders instead. And then the big bird knows they wont try and go after that feeder since there is another other one available that the big bird isn’t interested in cause he’s too busy eating. And defending his food. So the small birds don’t come less or stop comeing cause they can still get to the food. I don’t know if it will work for you or not but you could give that idea a try aswell