Any ideas about what to do with a robin that's established his breeding territory at the end of my house and his prime rival is his reflection in my sliding glass door?

I think you may find this useful. It recommends trying to put cling film or something over the outside of the glass to remove the reflection

I’ve heard of people putting cling on dots on the window, but I think @bongo has a better idea of an entire cling on to cover the door. Or, stop cleaning your door.~

I’ve always heard that images of large owls will work as effective bird deterrents.

I suggest filming it, and posting it on youtube.

@Adirondackwannabe, this behavior is most likely causing real internal damage to the robin. If you don’t want to put stickers on your glass, put a container with plants outside the glass sliding door. He will sit in the plants instead of trying to fly through your door. He is seeing the entire outdoors reflected in the glass and thinks he can freely fly in the direction of your glass doors.

Before you start spending money, you should ask yourself, is it because the reflection, or is he trying to fly inside because he can not see that there is something in the way.

Paint your window with peelable glass paint (but not until you’ve gotten video of the ordeal)