Woodpeckers, part of the family Picidae which includes piculets, wrynecks, and sapsuckers, are found globally except in Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. These birds primarily inhabit forests, but some can live in treeless areas like deserts, and the Gila woodpecker has even adapted to cacti. Recognized for pecking at tree trunks to forage for insects and larvae, woodpeckers communicate by drumming on trees, a sound audible from a distance. Their diets can include fruits, small animals, tree sap, and human scraps. Woodpeckers nest in holes they excavate in trees, which become habitats for other species once abandoned. Occasionally, woodpeckers come into conflict with humans by drilling into buildings or feeding on crops. The Picidae family, belonging to the Piciformes order, encompasses about 240 species in 35 genera, with nearly 20 species at risk of extinction because of habitat loss.
Woodpeckers possess varied sizes, ranging from the tiny bar-breasted piculet to the large great slaty woodpecker; their plumage too varies from drab for camouflage to conspicuous patterns with bold colors. Notably sexually dimorphic, these birds have zygodactyl feet (two toes facing forward and two back), enabling them to grasp tree trunks for vertical movement. These adaptations, along with their strong claws, legs, and stiffened tail feathers (except for piculets and wrynecks), allow for efficient climbing and pecking. Their beaks are strong and adapted for drumming and drilling, while their tongues are long and sticky, aiding in extracting food from crevices. Woodpeckers protect their brains from the impact of pecking through several anatomical adaptations. They also exhibit various flight patterns, are mostly sedentary, and prefer forests but can adapt to other habitats.
Woodpeckers engage in different behaviors, with some living solitarily while others form groups. Communication involves drumming and a range of vocal calls, with drumming serving as a territorial signal and part of courtship rituals. Most species feed on insects and invertebrates under bark and wood, playing a crucial ecological role in forest health by controlling pests. Breeding involves cavity nesting, mostly in trees, and they are predominantly monogamous, sometimes with cooperative breeding habits. The survival of woodpeckers is closely tied to the availability of trees for nesting and feeding.
Multiple studies have looked into the woodpecker's resistance to head injury from pecking, noting adaptations like spongy bone structure and uneven beak lengths that absorb impact energy. Furthermore, researchers have found tau protein accumulations in woodpeckers, akin to what is seen in human CTE, though the implications of this are not fully understood.