Drill, baby, drill: the influence of woodpeckers on post-fire vertebrate communities through cavity excavation

Several studies have addressed the importance of woodpeckers as ecological engineers in forests due to their excavation of cavities. Although research in green, unburned forests has identified the influence of different excavators on secondary use by cavity‐dependent species, little is known about the relative importance of cavities created by woodpeckers in recently burned forests. By excavating cavities, woodpeckers create habitat for secondary cavity users that can facilitate post‐fire regeneration through seed dispersal, seed germination and regulation of insect populations that affect vegetative growth. In this study, we monitored 77 cavities created by three species of Picoides woodpeckers for use by secondary cavity species in a fire that burned in the Sierra Nevada, California. At each cavity we measured nest tree and site‐specific parameters to determine if these characteristics could explain differential use by secondary cavity users. We found substantial overlap in cavity characteristics between woodpecker species, with the white‐headed woodpecker differing most notably in their placement of cavities in larger diameter, shorter and more decayed trees in less dense stands than either hairy or black‐backed woodpeckers. These differences in cavity placement may have resulted in the high diversity and large number of detections of secondary cavity species in white‐headed woodpecker cavities. Black‐backed and hairy woodpeckers were similar in the number of detections of secondary cavity use, although black‐backed woodpecker cavities were used by more species than hairy woodpecker cavities. Secondary cavity use was high (86%) suggesting these woodpeckers, and the white‐headed woodpecker in particular, can have an accelerating affect effect on ecological succession by providing valuable habitat features for seed dispersing birds and mammals, insectivorous birds, and small predators, thereby impacting ecological processes and functions.