House finches have a not undeserved reputation for being aggressive to other birds. Unlike most of the other visitors to our feeder they will stay on it and eat seed after seed. While they know their business, so to speak, I’m not sure this is the wisest strategy as we have hawks and the occasional coyote. Hiding in the nearby brush seems a safer idea. But then I’m not a house finch.
I’ve noticed that most of their aggression follows two paths. First, the females are rather bossy; they rather definitely rule the roost and will move male finches from their preferred perches. Second, the males are intolerant of other males, but mostly when there’s a female around. The males seem to have some sort of dominance structure themselves, but will settle down to the important business of feeding when there is no reason to fight.
I’ve added a slow motion video with narration (which you should feel free to turn off) that shows some of this behavior.