Woodpeckers Carry Fungus In Beaks That Promotes Tree Decay

The authors examined several species of woodpeckers living in ponderosa pine forests in northern California and Oregon, finding that over 60 percent of the sampled birds nesting in tree cavities had a variety of wood-inhabiting fungi living in their beaks.

These fungi serve a critical role in the decomposition of dead trees and influence how they are used by wildlife. Without adequate decay, woodpeckers are unable to excavate nest cavities – vital components of forests that serve as nesting sites to a variety of wildlife.

"Our study shows that woodpeckers are really the architects and landlords of the forest," said WCS scientist Kerry Farris, the study's lead author. "Their activities play a key role in how snags decay and are used by other species."

Woodpeckers initially puncture dead and dying trees in search of bark beetles and other wood-boring insects, a process that creates holes in wood that serve as infection sites for airborne fungal spores. As the birds return to these holes to feed, or to excavate them further for nesting, they pick up the fungi in their beaks, then help spread the spores by foraging on other dead trees.

While some forestry practices on public and private lands allocate a certain number of snags per acre for wildlife use, some recent federal policies call for removing snags because of their perceived risk in forest fires. The authors say that more factors need to be taken into consideration than just density or spatial arrangement of snags.

"Our research illustrates the numerous agents contributing to the complexity of snag decomposition and eventual cavity generation by woodpeckers," Farris said. "Forest management could benefit from a consideration of these processes when managing snags on public and private lands."