I feed sunflower hearts,it's definitely the little birds favourite,we have one of those iron hook hangers which is screwed to a big tree,so they swing freely but these crows have figured out how to cling on to them,I've already moved it as before it was on a tree next to a fence and they just used to jump from the fence onto the feeders but now they've been moved they have figured how land on them from nowhere,one bird does it then spills the seeds all over the ground and the rest come and eat them all,very clever but still infuriating