There is also a soft linen ceiling inside perhaps to keep the birdie from bumping his head. The center bump out comes out to allow for a large sized bird, either a chicken or a pigeon to exit/enter. There are a few perches and a swing which would make more sense for a smaller bird. 
 
I do not recommend using it for its original purpose. I have used it for many years as a plant display on the top of my bookcase as shown in picture 3. 
 
I originally bought this item from a barn during an estate sale over 20 years ago. I cleaned it up the best I could and have kept it displayed in my library. It has chipped and crackled paint. I considered spraying a clear coat of varnish to lock in the "history". 
 
Approximate measurements- 21"x12"x9"