The Piciformes group includes all species of woodpeckers, bearded woodpeckers, jacamars, barbacous and toucans. These species have important morphological differences, but they all have in common the presence of zygodactyl feet. This allows them to cling to branches easily. With the exception of jacamars, all Piciformes do not have downy feathers. Within this group, most woodpeckers are commonly known for their ability to quickly peck tree trunks with their beaks, making a drumming sound. Toucans, in contrast, have a highly developed, enormous and often colourful bill. This appendage is vascularised and allows them to thermoregulate. They form a sister group to Coraciiformes (rollers, common kingfishers, tree kingfishers, ground rollers, todies, motmots and bee-eaters).