In the still-stark days of early spring, it’s easy to see evidence of woodpecker activity in the Upper Delaware River region.  Swatches of light-colored wood catch the eye as one passes by a tree from which the bark has been stripped by a determined woodpecker intent on sourcing food.

Other animals such as porcupines, white-tailed deer, beavers and bears leave their marks on the stripped trees in our forests. Sometimes it’s challenging to determine which species has done what.

While it’s easy to identify the work of a woodpecker when one spots a rounded excavation peering like an eye carved into a tree, it can be trickier to tell when investigating an exposed swath. At first glance, the tree depicted in this column might appear to have been plied by a porcupine, but a closer inspection points to the more probable attention of a medium to large species of woodpecker.

In addition to carving holes, some woodpeckers harvest the larvae of wood-boring beetles or carpenter ants by removing the bark in a practice known as bark sloughing. The process calls upon the capacity of larger species that have the ability to hammer sideways across and under the bark, creating perpendicular slashes that can be mistaken for porcupine activity.

Bark sloughing is largely limited to foraging on dead trees, as the bark of living trees is too tightly bonded for easy removal by smaller species. Larger birds like the pileated woodpecker can be capable of removing bark from a tree that has recently died, in a process referred to as tight-bark sloughing.

Bark gleaning, also known as “Peer and Poke,” is a surface-foraging technique that allows the woodpecker to forage by peering and poking into bark with minimal damage to the tree. Small single holes resembling the tap of a nail into a stud (hunting impact marks) are created when a woodpecker taps a tree and listens for the sounds or movements of insects within.