Eastern Bluebird - Sialia sialis

This bluebird lived in my Mom's yard this past summer. But, unlike "normal" birds, it spent most of its time sitting on the outside of her windows trying to get inside. It will just sit and look in the window, flutter up into the air, and then sit back down. All the while, it makes little sounds. Then, it moves on to another window. Or, it perches on the hummingbird feeder, which is mounted on a window. Then, it will move to the door knob. It does this for HOURS everyday. Everyday!

It seemed that he had left in early autumn. But, now he's back. I spent the past couple days watching him and wondering what he is thinking/trying to do. He will literally sit on the window all day, staring inside. Every now and then, he flies off to the woods to eat some bittersweet berries, but then returns. My Mom contacted Audubon, but they have not responded with any suggestions or help.

Habitat: Rural backyard