They feed by flying just above the surface of the water with the open knife-like lower jaw cutting through the water. When a fish is encountered the jaw snaps shut. This Long-billed Curlew, like other shorebirds, has a long narrow bill for probing in mud and sand for insects and worms. The tip of the bill is very sensitive so the bird can feel when it touches its food. In some of these birds the tip of the bill can open to grab the food even when the rest of the bill stays shut.
Toucans feed on fruit and use the serrated edges of their bills to cut the fruit.
The main purpose of the large and colorful bill is for display, however. The bill is quite strong but very light weight since it is not solid bone, but has a honeycomb of bony struts inside. Some birds beaks are used for things besides getting food. The Puffin has a large bright red bill which is used for courtship display. During the winter the colorful outside pieces fall off and the bill is smaller and dull colored.