We have a Summer Tanager who has taken up residence near our deck. As they are prone to do, he is flying into our windows, hitting them with his beak. We think he sees his reflection and thinks he must attack his competitor.
Here is an image of a Summer Tanager from the web:
And here are a couple of pics I took of our guest, on our deck railing:
We keep thinking he will wear himself out and give up. But he is convinced that he must fight off that other persistent male!