Bird nest
Puffins, for instance, dig a tunnel that is usually two to three feet long. At the end they make a nest of feathers and grass and lay their eggs. They are able to do this because of their sharp bill and claws. A puffin can work for hours to make its tunnel. Kingfishers, too, dig or burrow their holes. They can burrow up to six feet into the side of a cliff and lay their eggs in that place.