Nuthatches, like this White-breasted species, have evolved a special feeding technique -- working from the top down. You've seen them, upside down on a tree, poking behind pieces of bark, looking for insects missed by bird species that work from bottom up or simply work at the landing point. This nuthatch, at one of our feeders, takes seed in the same fashion, even though it's not necessary. It's just the way it's done. The bird(s) do also feed like their feeder companions, this House Finch for example.