Woodpecker woes: the right tree can be hard to find

Abstract

Woodpeckers and other cavity-excavating birds worldwide are keystone species. These birds excavate their nests out of solid wood, and because their nests are often well protected against predators and the environment, other species use and compete for their old, vacant nests. The presence of cavity-excavating birds in forests has far-reaching effects on species richness and ecosystem health.

Given the species’ importance, Teresa Lorenz, a research wildlife biologist with the U.S. Forest Service Pacific Northwest Research Station wanted to find out why cavity-excavating birds do not use many trees seemingly suitable for nesting. This puzzle has eluded researchers for decades. Lorenz and her colleagues also wanted to know what role wood hardness plays in the birds’ nest site selection.

The resulting study in the eastern Cascades of Washington found that cavity-excavating birds preferred to nest in trees with significantly softer interior wood. The researchers also found that at-risk species were nesting within burned areas where up to 96 percent of the trees had unsuitably hard wood. This suggests that many trees and snags previously considered suitable for cavity-excavating birds actually may not be.

In dry forests, prescribed mixed-severity fire may be a useful tool for creating suitable nesting habitat for cavity excavators.

Citation

Vizcarra, Natasha; Lorenz, Teresa. 2017. Woodpecker woes: the right tree can be hard to find. Science Findings 199. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 5 p.