But... why is that bird doing that?

After the picture went viral on Twitter, experts guessed what the bird might be doing, including 'showing off' or flipping over as a way to slow itself down while flying.

"They told me it's called "whiffling'," says Cornelissen, explaining the unusual method of a bird slowing down.

"A professor of the University of Istanbul told me he believes in the whiffling theory because the turning causes down-force on the wings. He even uses this picture in his lessons.

"A bird professional in the Netherlands says it's probably a way of showing off to his fellow geese. I don't know what is true, I like both explanations."