The woodpecker family (Picidae) consists of specialized avian species found across the globe, with the notable exceptions of Australia, New Zealand, and Antarctica. They are instantly recognizable by their unique and powerful behavior of striking wood with their beaks. This high-impact action is a suite of distinct behaviors that allows them to thrive in their ecological niche. Woodpecker activities center on using specialized anatomy to navigate, communicate, and subsist within wooded environments.
Foraging for Food
The most frequent reason a woodpecker strikes wood is to forage for prey, primarily wood-boring insects and their larvae. This involves slower, exploratory pecking to locate insect tunnels beneath the bark or within the wood. Once a food source is detected, the pecking becomes a deliberate excavation to drill a hole into the tree.
After creating an opening, the woodpecker relies on its tongue to extract its meal. This organ is supported by the hyoid apparatus, a complex structure of bone, muscle, and cartilage. The hyoid features long, flexible “horns” that wrap around the skull, allowing the tongue to extend significantly beyond the bill, sometimes up to five inches in certain species.
The tongue is highly adapted for retrieval, often being sticky due to specialized saliva and equipped with tiny barbs at the tip. These features allow the bird to probe deep into the wood and secure the insect. While most species are insectivores, some, like sapsuckers, lap up tree sap, and acorn woodpeckers cache nuts in specialized storage trees called granaries.
Drumming and Communication
In contrast to the slow pecking used for feeding, woodpeckers engage in a rapid, rhythmic behavior known as drumming. Drumming is a communicative signal, similar to the songs of other birds, and is performed by both males and females. It is primarily used to announce presence, establish territorial boundaries, and attract mates, making it a seasonal behavior.
The goal of drumming is sound, not excavation, so woodpeckers select highly resonant surfaces to amplify their message. These surfaces often include hollow tree trunks, dead branches, or human-made structures like metal gutters and signs. Each species possesses a distinct drumming pattern, characterized by variations in speed and rhythm, which helps communicate their species identity. This rapid striking is considered an exaptation, a ritualized version of foraging pecking that evolved to serve a new communicative function.
Creating Shelter and Nesting Cavities
Woodpeckers are primary cavity excavators, creating their own holes for both roosting and nesting. These cavities are distinct from foraging holes, requiring significant time and effort to carve out a spacious interior. Site selection is careful; birds often choose trees with softer, diseased wood for easier excavation while maintaining enough sound wood for structural integrity.
The excavation process can take anywhere from a few weeks to several years, depending on the species and wood hardness. Woodpeckers often create multiple cavities in their lifetime, which are abandoned after initial use. These abandoned holes are ecologically significant, providing homes for over 35 species of secondary cavity nesters, such as owls, bluebirds, and small mammals, which cannot excavate their own shelter.
Specialized Physical Adaptations
The ability to strike wood at high speeds without injury is enabled by specialized anatomical features that absorb impact. During a pecking event, a woodpecker’s head can experience a deceleration up to 1,200 times the force of gravity (1,200 g). The skull contains spongy, plate-like bone structures that act as a shock absorber around the brain.
The hyoid apparatus, in addition to supporting the tongue, also functions as a flexible “seat belt” that wraps around the skull, helping to dissipate impact forces. The brain itself is small and tightly fitted within the cranium, with minimal cerebrospinal fluid. This limits brain movement and reduces the risk of concussion. Neck muscles are reinforced to resist rotational forces. Furthermore, the upper and lower halves of the beak are of slightly unequal length, which helps distribute vibrational energy away from the brain.