I haven't gotten a bird bath heater yet. We do feed birds tho. Yesterday I saw 3 bluebirds eating the sumac berries! Also a nuthatch on the suet bar. I don't know where the Christmas cardinals are ?
Titmice and a finches also. My favorites might be the woodpeckers. We have the pilated ones, they nest in our woods in old snags that are left. They don't come to the feeders but I have seen them on the electric pole!