Piciformes nest in holes called cavities, but how they get the cavities varies. Woodpeckers and some barbets use their sharp bills to chisel out their own cavities in trees. Jacamars and puffbirds tend to dig nesting cavities in softer ground or dirt banks. Toucans colonize old woodpecker cavities or other tree holes, rather than excavate their own. Honeyguides hijack the nests of other birds, laying one egg per nest that will yield a honeybird hatchling that may kill the host hatchlings. Regardless, piciformes tend to have large bills adapted for gouging into things. All piciformes have a special foot with two toes facing forward and the other two backward (zygodactylous), in contrast to the usual bird arrangement of three forward and one backward. Piciformes can often be spotted climbing vertically up and down tree trunks.