Woodpeckers are known for their distinctive pecking against tree trunks. This persistent activity serves various specific purposes linked to their survival and daily lives. These functions reveal the intricate relationship between these birds and their arboreal environment.
Pecking for Food
Woodpeckers primarily peck at trees for food. They often target wood-boring insects, such as beetle larvae, ants, grubs, and caterpillars, that reside beneath the bark or within the wood itself. Woodpeckers locate these hidden meals by tapping on surfaces and listening for subtle sounds of insect movement or for hollow areas that might indicate an infestation. Once detected, they use their strong, chisel-like bills to excavate holes, then extract the prey with their long, barbed tongues.
Some woodpecker species, notably sapsuckers, also peck to access tree sap. These birds drill rows of small, precise holes, known as sapwells, into the bark to allow the sugary sap to flow out. They then return to lap up the sap with their specialized brush-tipped tongues. These sapwells additionally serve as traps for insects attracted to the sweet liquid, providing an extra source of protein for the woodpeckers.
Communication and Territory
Not all pecking is related to foraging; woodpeckers also engage in “drumming” for communication. This drumming involves rapidly striking their bills against resonant surfaces, producing a distinctive sound. Its purpose is to declare territory, attract mates, and communicate with other woodpeckers.
Woodpeckers intentionally select surfaces that amplify sound, such as hollow tree trunks, large branches, or even human-made structures like metal gutters, chimney caps, or utility poles. Both male and female woodpeckers participate in drumming, especially during the late winter and early spring breeding season. The specific tempo, rhythm, and duration of drumming patterns can vary between different woodpecker species, acting as a unique auditory signal.
Nesting and Roosting
Woodpeckers also peck to create cavities in trees, which serve as safe spaces for nesting and roosting. Unlike many other cavity-nesting birds, woodpeckers excavate their own homes. They typically prefer dead or decaying trees because the wood is softer and easier to chisel.
The excavated cavities usually begin with a round entrance hole, leading to a deeper vertical chamber. Woodpeckers do not bring in additional nesting materials; instead, wood chips created during excavation cushion their eggs. While a pair might use one nest cavity per breeding season, individual woodpeckers often create multiple roosting cavities, particularly in the autumn, to provide shelter from predators and harsh weather conditions. These abandoned cavities are frequently reused by other wildlife that cannot excavate their own.
Effects on Trees
Many people wonder if woodpecker activity harms trees. In most instances, pecking does not cause significant damage to healthy trees. Woodpeckers often target trees that are already weakened or infested with insects.
However, extensive pecking, especially by sapsuckers creating numerous sapwells, can potentially reduce a tree’s vigor or create entry points for diseases and pests. In rare cases, continuous rows of sapwells encircling a tree can girdle it, disrupting the flow of water and nutrients and leading to decline. While foraging holes are typically small and scattered, the larger cavities created for nesting and roosting are generally found in dead or decaying wood, which poses less of a threat to a tree’s overall health.