Woodpeckers are a familiar sight and sound in many natural landscapes, distinguished by their rhythmic hammering against trees. This distinctive behavior raises a central question: why do these birds repeatedly strike wood? Their pecking serves multiple purposes, integral to their survival and communication.
Primary Motivations for Pecking
Woodpeckers primarily peck wood for foraging, creating nests, and communicating with other birds. Foraging involves drilling into wood to find insects hidden beneath the bark or within the wood. Their long, barbed tongues then extract the prey. Some species, like sapsuckers, create small, neat rows of holes to access tree sap, which also traps insects for consumption.
Beyond finding food, woodpeckers excavate cavities in trees for nesting and roosting. These cavities provide shelter for raising their young and a secure place to sleep. Both male and female woodpeckers participate in this demanding task, with nest cavities often taking one to three weeks to complete. They prefer dead or diseased trees, as the softer wood makes excavation easier, creating a safe, unlined chamber for eggs and nestlings.
Rapid, resonant pecking, known as “drumming,” serves as a form of communication. Unlike the slower pecking for food or nests, drumming is a territorial display and a way to attract mates, especially during the breeding season. Woodpeckers choose surfaces that amplify sound, including hollow trees, branches, and human-made structures, to ensure their message carries widely. Both sexes engage in drumming, establishing their presence and warning off rivals.
Ingenious Adaptations for Pecking
Woodpeckers possess specialized physical adaptations that allow them to peck vigorously without injury. Their skull structure includes extra plates of spongy bone, once thought to act as shock absorbers, but now understood to enhance pecking performance as a stiff hammer. The brain’s small size and tight fit within the skull also protect it from deceleration forces.
The elongated hyoid bone is another adaptation, originating in the nostril and wrapping around the skull, sometimes encircling the eye sockets. This structure helps anchor the tongue and, when muscles contract, stabilizes the skull and spine during impact, similar to a seat belt. This allows the woodpecker’s tongue to extend beyond its beak, reaching deep into crevices to retrieve insects. Different species have specialized tongue tips, such as barbs for grasping insects or a brush-like tip for lapping sap.
Powerful neck muscles enable the rapid, forceful pecking motion, allowing the bird to strike wood with considerable impact. Their feet are zygodactyl, meaning two toes point forward and two point backward, providing a strong grip and stability on vertical tree trunks. Stiff, wedge-shaped tail feathers act as a prop, bracing the bird against the tree and providing support and balance during pecking.
When Woodpecker Pecking Becomes a Problem
While woodpecker activity is a natural part of forest ecosystems, it can sometimes lead to concerns for humans. Excessive pecking, particularly by sapsuckers, can damage trees by creating holes that allow diseases or insects to enter, potentially weakening branches or the entire tree. Healthy trees can often withstand woodpecker activity, and holes may indicate an existing insect infestation.
Woodpeckers occasionally peck on human-made structures like houses, siding, eaves, or utility poles. This behavior can be driven by a search for insects, an attempt to excavate a nesting or roosting cavity, or for drumming to communicate territory or attract a mate. Siding made of rough-sawn plywood or natural wood is more susceptible to damage.
When pecking on structures becomes problematic, various strategies can be employed to deter them. Visual deterrents, like reflective tape, windsocks, or Mylar balloons, can discourage their presence. Covering affected areas with bird netting or physical barriers can prevent access. Addressing underlying insect infestations may reduce the woodpecker’s motivation to peck.