Among Downy Woodpeckers, males defend their territory against other males, and females defend against other females. When an intruder enters a Downy's territory, the resident woodpecker displays threateningly, holding its bill high, flicking its wings, and/or fanning its tail, all in an attempt to drive the trespasser away. This went on for quite some time. The intruder flitted from branch to branch, tree to tree, but would not leave. The resident woodpecker followed his every move. I ended up having to leave before the intruder woodpecker did!
Note the fanned tail.
This was the first time I have seen this, and it was fun to watch!