In the systematics of birds, the woodpeckers (Picidae) are a species-rich family from the order of woodpeckers (Piciformes). This bird family contains 28 genera and more than 200 species. In addition to the true woodpeckers (subfamily Picinae), the subfamily lesser woodpeckers (Picumninae) and the species-poor subfamily of turnstones (Jynginae) also belong to the family.
Woodpeckers are elongate-bodied birds with strong, straight, angular chisel bills that are nearly as long as the head, especially in the Pileated Woodpeckers (Picinae). The skull has special adaptations that serve to dampen vibrations without, however, absorbing too much kinetic energy during the species-typical knocking against wood. The thin, flat and horny tongue is widely extensible and has short barbs at the end.
The wings are of medium length and somewhat rounded. In pileated woodpeckers, the tail is wedge-shaped with stiff, pointed control feathers. It serves as a support when they climb up tree trunks.
The short feet usually have paired toes with strong claws, two pointing forward and two pointing backward. However, some species, such as the Three-toed Woodpecker (Picoides tridactylus) have only three toes, two pointing forward and one pointing backward.
Woodpeckers are distributed almost worldwide. However, they are absent in areas where there are no or hardly any tree stands, such as tundras, deserts and steppes; but there are also land masses with forests where woodpeckers are absent. These include Australia, New Guinea, New Zealand, Madagascar, and the Pacific islands.
With over 100 species, the family is richest in South America and Central America. The Lesser Spotted Woodpecker subfamily is found only in the tropics of the Americas, Africa, and Asia. Turning-necked woodpeckers are found only in the Old World.
The Great Spotted Woodpecker is by far the most common woodpecker in Central Europe, followed by the Black and Green Woodpeckers. There are also wrynecks, gray woodpeckers, middle-spotted woodpeckers, lesser spotted woodpeckers, three-toed woodpeckers, white-backed woodpeckers, and great spotted woodpeckers in Central Europe.
Woodpeckers usually live singly or in pairs in forests, tree plantations and gardens. They form larger groups only exceptionally outside the breeding season. Woodpeckers move almost exclusively by climbing; they hop around clumsily on the ground and rarely fly long distances.
A distinctive feature of woodpeckers is that they use considerable force and endurance to tap their beaks against tree trunks, chipping the wood to find food, “carve” nest cavities, mark their territory, or attract sexual mates. These activities are also called chiseling (chipping) and drumming (courtship behavior). It has been reported that the pileated woodpecker (Dryocopus pileatus) bangs its beak against wood up to 12,000 times per day, and it is surprising that its brain is not damaged by these blows.
A woodpecker can make up to 20 blows per second, and each blow, according to a report in the scientific journal Nature in October 2006, is comparable to a 25 km/h impact of the beak against a wall, whereby a deceleration of up to 1,200 g can become effective – a deceleration several hundred times greater than astronauts have to endure during a landing from space. At the same time, Nature referred to several scientific publications that explained why woodpeckers do not get headaches despite these stresses. For one thing, woodpeckers’ brains are surrounded by particularly little cerebrospinal fluid: Their brains thus sit relatively rigidly in the skull and are not hurled against the skullcap from the inside by the shock waves generated by tapping, thus preventing concussion. Furthermore, the skull is surrounded by remarkably strong muscles that act as shock absorbers: Like a boxer who sees a punch approaching, these muscles tighten against the wood just before impact, absorbing much of the energy. In addition, the tapping motion is executed in an extremely straight line, from the shoulder, so to speak. This keeps the neck and head rigid with each other, and any horizontal or vertical rotation of the head is avoided, so that only small shear forces can act. Finally, a woodpecker closes its eyes a millisecond before impact, protecting them from flying wood chips. In 2022, another study confirmed this reasoning.
Most species feed on insects they find in or under tree bark or bark or in rotten wood. To do this, they climb up trees and look for hollow places by tapping the trunks with their beaks.
Some species, such as the wryneck (Jynx torquilla) or the green woodpecker (Picus viridis), live mainly on ants and their pupae, which they search for on the ground. In some species, especially American sapsuckers (Sphyrapicus), tree saps make up a larger part of the diet, which they make flow themselves by ringing the trunks with their beaks. Some species also eat fruits and seeds of plants, buds, and fungi, and create pantries.
Great spotted woodpeckers, for example, press hazelnuts or pine cones into tree crevices (which they sometimes even create themselves beforehand by chiseling a corresponding notch in the trunk or a branch) in order to knock the objects fixed in this way open with their beak, which in turn other birds, for example magpies, take advantage of in order to get at the contents of the nut after the great spotted woodpecker has been driven away. Occasionally they also help themselves to tit dumplings.
The woodpeckers are cavity breeders. The breeding cavities are usually carpentered in tree trunks by the true woodpeckers themselves. They are lined with only a few chips. The woodpeckers lay three to eight white eggs, which are hatched by both sexes. The nestlings are then immediately provided with food. The young birds are also called nestling birds, which means they stay in their mother’s burrow for some time. When they have fledged, they are driven out of the nest cavity by the parent birds.
Woodpeckers also use composite thermal insulation systems on buildings to create nesting cavities. This results in so-called woodpecker damage.