Woodpeckers and their relatives nest in holes or cavities. Woodpeckers and barbets chisel out their own nest-holes using their dagger-like bill. Some species are rather anti-social in their habits and show aggression towards other woodpeckers (including those of their own species). Other woodpecker species are more social and live in groups that breed communally. Some woodpeckers gather with other species of birds in mixed flocks.
Like parrots, woodpeckers and their relatives have zygodactyl feet, which means that of their four toes, two face forward and two face backwards. This arrangement enables woodpeckers to grasp onto and climb tree trunks with ease. It should be noted though that there area a few species of woodpeckers that have only three toes (they are know, not surprisingly, as the three-toed woodpeckers).
Many woodpeckers and their relatives have strong legs and a sturdy tail, both adaptations that enable them to grasp tightly to vertical surfaces such as tree trunks. Since woodpeckers hammer their bills against the tree trunk to dig out insects or build nests, they have specially adapted skulls which protect the brain by cushioning the impact that repeated pounding inflicts.
Bill shape varies widely among members of the group. Woodpeckers have a chisel-like bill that is long and sharp. This enables woodpeckers to hammer and chip away at the bark of trees to get to insects and grubs hidden within. Toucans have a long, broad bill with serrated edges. The toucan bill is well-suited for grasping fruit from branches and tearing it apart. Puffbirds and jacamars capture their prey in mid-air, catching flying insects with their sharp, slim bill.
The smallest species of the woodpeckers and their relatives is the rufous piculet (measures just over 3 inches in length). The largest is the toco toucan which can grow to more than 24 inches in length.
Most woodpeckers and their relatives feed almost exclusively on insects, grubs and other arthropods. They forage on tree trunks of both dead and living trees.
The barbets and toucans are the exceptions among the otherwise insect-eating woodpeckers. Barbets and toucans feed on fruit. The honeyguides are also unique, they feed not only on insects but also on beeswax.
Woodpeckers and their relatives are found in most parts the world but are absent from oceanic islands as well as Australia, Madagascar and Antarctica. Among the various subgroups, the woodpeckers are widespread, piculets inhabit tropical regions within Southeast Asia, Africa and South America, and wrynecks occur throughout Europe, Asia and Africa.
Woodpeckers and their relatives prefer woodlands but live in a variety of habitats such as temperate forests, tropical rainforests, savannas, bamboo forests, deserts and scrublands. Woodpeckers and their relatives include species that are migratory as well as those that are sedentary.
The woodpeckers and their relatives include two living groups. The first, the Galbulae, include the jacamars, puffbirds, nunbirds and nunlets (a total of about 50 species). The second, the Pici, include African barbets, Asian barbets, toucans, toucan-barbets, American barbets, woodpeckers, piculets, wrynecks and honeyguides (a total of about 350 species).
The closest living relatives of the woodpeckers and their relatives are the perching birds and the kingfishers. Woodpeckers and their relatives belong to a group of birds known as the Neognathe, a clade that includes nearly all living birds with the exception of the kiwis, ostrich, rheas, cassowary and tinamou.