This usually happends when a guy with big hands (which of course means big fingers) flicks you off. His fingers are so huge, a "bird" just isn't big enough. Also see Flipping the Hummingbird for the smaller version.

Anatidaephobia is defined as a pervasive, irrational fear that one is being watched by a duck. The anatidaephobic individual fears that no matter where they are or what they are doing, a duck watches.

Anatidaephobia is derived from the Greek word "anatidae", meaning ducks, geese or swans and "phobos" meaning fear.