Throughout the weekend though, a particular robin had come back to that window every 10 minutes only to repeatedly fly into it for about 30 seconds before we would chase him away.
I've read that male robins make it their mission to defend their territory from those who dare to encroach during nesting season. When they see their reflection in a window they believe it is another robin, and the closer they get to that "intruder" the more it looks to them as if the intruder is challenging them back! It's an endless cycle of wrongly perceived threats that ends with the robin attacking his own reflection. In our case, that robin has been battling himself for almost a week.
On Memorial Day, this robin was unstoppable. At first his misguided valor was funny. By mid-afternoon, however, humor was replaced with sheer aggravation as that bird flopped into every last nerve we had.
I placed a deck chair against the window to see if it would block enough of the reflection but soon realized the chair had become a handy, bird-poo-covered perch for him to rest on while he stared his enemy down. I put paper over the window and it seems to have helped.
As soon as his brood hatches his attention will turn to caring for his family. The average robin egg incubation period takes about 12-14 days, so we may endure another week of this crazy behavior.