Pileated woodpecker nest testing

Pileated woodpeckers in this area often nest in a living aspen infected with a fungus called Phellinus tremulae. The fungus attacks living trees and rots the heartwood inside an outer shell of sound living sapwood. The fungus forms hoof-shaped fruiting bodies on the outside of the tree called conks. Hence the common name for this fungus - the horse-hoof conk. Although they are strong enough to chip away at very hard wood, even pileated woodpeckers don't like to excavate their nest cavities entirely in hard wood. Large aspens with heartrot are their favourite.

Each spring mated pairs explore for possible nest trees. They are well into the process for this spring, and yesterday I found a test excavation behind Maxwell Lake. There were actually 3 test holes on one tree. Perhaps the tree didn't have enough rot, because I couldn't see any fungal conks on the trunk and the chips on the ground were sound. There is dark hardwood at the back of the excavation however, which might mean rot is present. I'll keep watching the tree to see if the woodpeckers agree with me or not.

Sometimes a woodpecker pair will return years later to an old abandoned start and complete it for use as a nest cavity. There's some evidence to suggest that the original test hole might have actually introduced the fungus to the tree, in which case the woodpeckers are helping their own cause. Clearly the original tree met their requirements, but it didn't have enough rot. No problem, just inoculate the tree and come back later. A neat process to ensure a long-term supply of suitable nest trees.