During the fall dispersal period, some young grouse crash into buildings, trees or through windows in a so-called "crazy-flight." Both of the birds that flew through my windows were young of the year birds.
Others that I heard about in the area were young of the year birds also. It wasn't an uncommon thing in my area. Fairly often I would hear of a grouse crashing through a window.
But your bird was a different story. I still think he was trying to get in for more seed.
