Bar Entrance

Alright, listen up, you dummy. The joke is that "ducked" sounds like "walked" but also means to lower your head quickly to avoid being hit. Get it? Three birds go into a bar and instead of WALKED, the dude say's DUCKED, because a "swan, a goose, and a penguin" are all ducks. So instead of a bird using its LEGS to get into a BAR it uses its wings! You probably don't get it because your mother was a hamster and your father smelled of elderberries.