Woodpeckers as ecosystem engineers

Background/Question/Methods

Woodpeckers are among the most striking examples of ecosystem engineers because they excavate their nest cavities in heartwood of trees, consequently providing a valuable supply of tree holes exploited by many other cavity-nesting species. In western North America, for example, at least 32 bird species, 12 mammal species, and several invertebrate species nest in cavities created by Red-naped Sapsuckers, Northern Flickers, and other woodpeckers. The last two decades have seen an increasing amount of research on cavity-nesting species. These studies have, for example, described nest webs (communities of producers and users of tree cavities), elucidated important factors in nest-site selection, quantified longevity of cavities, analyzed the effects of forest pests, suggested management strategies, and identified conservation priorities. While woodpeckers undoubtedly provide important ecosystem services—for example, some of the most common and welcome visitors to bird feeders are woodpeckers and secondary cavity-nesting species (e.g., chickadees and nuthatches)—few if any published studies have explicitly appraised these services.

Results/Conclusions

We review the current state of knowledge of ecosystem services provided (directly and indirectly) by woodpeckers and suggest directions for research that will help quantify the value of these services. We also discuss some poorly understood factors influencing cavity-nesting communities, such as the ecology of heartwood-decaying fungi.