The doves try to dominate the flat feeder, and this red-headed woodpecker is having none of it. He has crouched down and prepared to take a bite out of the dove that is trying to push him out.
These little skirmishes go on day in and day out. Doves sit and eat rather than perch and eat, so they will camp out in the feeder and not let anyone in unless I shoo them away.
Since their behavior is so obnoxious, I wish they would take their voracious appetites elsewhere.