You can reduce the problem, by the means suggested above, but you may not solve it altogether. We don't get starlings. No, we get rooks ! You'd never think that a rook would bother with a wire mesh feeder but ours do.It's pure mischief, because there's usually food thrown out,on the ground, for them.One gets on the feeder and attacks it, thereby shaking and swinging it enough that part of the contents falls out. Its pal, standing underneath, then eats the fallen supply! LOL Our jackdaws make a similar effort. I've not worked out whether the pairs take turns or whether the shaker gets anything directly, but, given recent research on rook intelligence, it wouldn't be surprising if they do work as a team.