Does anybody have ever seen bird(s) that fly upside down?

 

I never see any.

 

I think bird's anatomy itself do not let them fly flipped upside down. But maybe I am wrong.

 

Sorry, it is a stupid question. But, I think it is interesting.

this is what google picked up: http://www.enature.com/expert/expert_show_question.asp?questionID=7161

Think about a bird's flapping wings and which way the power of the thrust goes. Also think about a bird gliding (without flapping it's wings) and how it's wings are held when it glides.

 

None of this can be reversed effectively by the bird and still maintain flight. They just aren't built for it.

I have seen film footage of birds flipping upside-down deliberately to present their talons to an attack from above. Not sustainable flight, perhaps, but they seem quite adept at doing it when necessary.

Thank you for the answers. I got the idea now.