Pic I Found Online

[wei0204]

Something different but awesome...

 

[Yazan]

looks like the bird cage is behind the tank but the reflection on the gravel makes it kind of look like theres gravel on the bottom of the cage. good pic

That mite be it.

 

[jakeroberts]

um if u look clocly the cage has been made watertight and then it has been put in the and has had somthing to hold it down and the birds can breath from the top of the cage

 

[Synirr]

AWESOME pic, that's fantastic. The colours of the birds and fish coordinate so well!
"A bird may love a fish, but where would they build a home together?"

I'd imagine this setup is all one piece, rather than being a separate acrylic/glass cage submerged in the tank. If you look closely at the edges of the setup you can see that the bird area is sort of inlaid into the fish part of the tank.
Quick drawing of how this setup appears to be done.

 

[Tokis-Phoenix]

Awesome tank, would love to see one for real, combine two great hobbies- fishkeeping and bird keeping!