A woodpecker is a bird that hits tree trunks with its hard, pointed beak, again and again, very fast. It does this for three reasons: to make a hole to live in, to dig out insects hiding under the bark, and — this part surprises people — to make noise on purpose, because the drumming sound is how it calls to other woodpeckers, the way other birds sing. So the noise is partly its song. Its tongue is very long and sticky to pull insects out, and its tail is stiff so it can lean back on it like a third leg while climbing straight up the trunk. Woodpeckers are common in America, Europe and Japan, and there are a few kinds in Taiwan's mountain forests, though most people here have only heard one and never seen it. In everyday English the word is also used for the sound: if someone says 'there's a woodpecker outside my window at six in the morning', they usually mean the knocking, not the bird itself.