Summer tanager obsessive behavior (1 Viewer)

[scatterbug]

I have an east wall made up of windows. To prevent bird hits, I have strings hanging across the windows & have not had problems. For the last 4 days a pair of tanagers have continued to fly from one side to the other holding on to the string tapping against the window. i do not have plants inside & can’t figure the draw. Suggestions? East Texas

 

[Mono]

It is often territorial, the birds are seeing their reflection and acting aggressively toward it. I don't know if Tanagers are prone to this but many bird are.