Laura Erickson's For the Birds

Woodpeckers and fungus

It’s impossible to study forest ecology, looking at the interdependence of trees with other plants and animals, without considering the critical importance of woodpeckers. These handsome and interesting birds not only provide nesting sites for many other animals besides themselves in their excavated holes, but they also remove wood-boring beetles, carpenter ants, and other destructive insects, sometimes saving trees that would otherwise most certainly be doomed by insect pests. One group of woodpeckers, the sapsuckers, drill holes that allow sap to run out, the way people tap maple trees for syrup. The trees usually survive, and the running sap provides food for warblers, phoebes, kinglets, and hummingbirds when they first return in spring, before flowers open. And when branches or trees do die, woodpeckers bore through the dead wood to get bugs, breaking down the wood to help the decomposition process. And, according to an article that was just published in The Condor, the journal of the Cooper Ornithological Society, woodpeckers contribute to that decay process in another way as well, helping a huge variety of fungi at the same time.

Apparently, a woodpecker’s beak can be a lush garden of fungus spores. In the study, scientists from the Wildlife Conservation Society and Arkansas State University sampled woodpeckers living in ponderosa pine forests in northern California and Oregon, and found that over 60% had a variety of wood-inhabiting fungi spores living right in their beaks. This is obviously beneficial to woodpeckers—some of the spores are transferred to bark when the woodpeckers are probing near the surface for insects. The fungus in turn starts working on the outer wood, and as it decays, more insects can invade, providing more food for the woodpecker, and ultimately the tree will have enough decay to make excavating a nesting cavity easy. How do the woodpeckers get the spores in the first place? Apparently as they tap snags and rotten wood for bugs, they pick up spores, and then transfer them to other trees.

Although rotten trees seem to be a bad thing, when wood dies and rots away, the nutrients return to the forest soil. And after trees fall in windstorms, the quicker they rot away, the smaller the risk of fires. So fungus transfer by woodpeckers is a very important process in forest ecology, but one that is just now getting serious study. We humans like to think we are forest managers, but the truth is we don’t understand the implications of much of what we do. As much as we already know, there is a great deal more to learn about the intricate connections between the animals and plants of our forests. Wildlife Conservation Society researcher Kerry Farris, the study’s lead author, noted that this research “illustrates the numerous agents contributing to the complexity of snag decomposition and eventual cavity generation… Forest management could benefit from a consideration of these processes … on public and private land.” As Farris notes, “Woodpeckers are really the architects and landlords of the forest.”

In the mythology of ancient Rome, the Saturn’s son, Picus, was a beautiful forest god who could foresee the future. When the sorceress Circe tried to seduce him but was rejected, she angrily transformed him into a woodpecker. It’s fitting that these birds that dig through tree rings of past years not only see into the future but also provide for it, both by constructing cavities and providing the mechanisms for making cavities easier to build. And these gentle, focused birds provide not only for themselves, but also for the many other forest creatures who live in woodpecker holes, from flying squirrels and some mice to little owls. And, of course, fungus. The ecological importance of woodpeckers is, literally, mushrooming.