All true with many birds and male Cardinals seem normally even more so. That said, the two feeders in our back yard have been a lifeline this winter to our fine feathered friends. We have at least four and five males at one time eating or waiting their turn on the one feeder and I have seen up to three female cardinals at one time as well. They all seem to get along with no issues. As for the rubbing of the beak on a tree branch, I have seen others doing that as well and wondered if it may be like us rubbing our nose or something like that.