Source: Woodcraft Folk Games Games Games
Players line up at one end of a hall/space. There is a Caller who stands to the side.
The Caller shouts e.g. "Fly, fly blackbird!". All the players run to the other end of the hall and back, because blackbirds fly.
The Caller can also shout e.g. "Fly, fly car!" though. In which case the players should stay still, because cars don't fly. If a player does move at this point they change places with the Caller.
Die Vögel Fliegen Hoch!!!