It looks like he is wearing a yellow Batman mask over a black cap. He was smaller than a goldfinch and larger than a hummingbird.
He wasn't very happy with me holding him. When he finally escaped from my grasp, he flew a lap around the garage (I'm sure he saw my baby quail in a cage and thought he had barely missed that fate!), found the door and was gone.
I have searched my bird books but have had no luck in identifying him. If you know what type of bird this guy is, please let me know. I want to add him to my "Look What I Saw" list!
Note: Even though it looks like I'm squishing him in the photos, I promise he was not injured!
Thanks to Katie, Terri, Sharon, and 437 for identifying this guy! He is a male hooded warbler. He was probably heading south for the winter when he slammed into the window in the chicken house and couldn't figure out how he got in there! Let me think of some other questions I want answers to and get them posted.