White-headed Woodpecker Home Ranges in Managed Ponderosa Pine Forests

Project abstract:

White-headed Woodpeckers (Dryobates albolarvatus) are important cavity excavators that recently have become the focus of much research because of concerns over population declines. Past studies have focused on nest site selection and survival but information is needed on factors influencing their space use when away from the nest. We examined space use by White-headed Woodpeckers during the nesting (May–Jul) and post-nesting (Jul–Oct) periods and compared the role of environmental factors (e.g., landcover) and socio-demographic factors (e.g., age, breeding success) in home range size and selection of location. We also investigated foraging substrate use by adult white-headed woodpeckers during the nesting and post nesting periods (May - October).

Project goals:

Our first objective was to obtain base-line information on White-headed Woodpecker home range size in managed stands for comparison with other studies, because past studies have focused on their space use in forests with an old-growth component. Our second objective was to examine factors associated with variation in home range size. We were particularly interested in the degree to which socio-demographic factors such as bird age, population density, and nest productivity influenced space use compared to environmental factors such as stand age, tree size, and availability of old-growth forest. Third, we tested for selection of habitat features on the landscape for home ranges (second-order selection) during the nesting and post-nesting periods. Because old-growth forest was rare in our study areas, we were interested in determining features selected by White-headed Woodpeckers in landscapes lacking large, old trees. Our fourth objective was to characterize both substrate use and size of trees used for foraging in areas that had been harvested and/or burned, and which generally lacked the large trees (e.g., 68 cm diameter). Our fifth objective was to model habitat selection by foraging white-headed woodpeckers during two time periods, the nesting period (combining the incubation and nestling periods) and post-nesting period (combining the fledgling and post-breeding autumn periods). Our final objective was to examine whether differences in foraging behavior affected one important measure of population growth, number of young fledged from nests.

Project plan:

There is limited information on space use by White-headed Woodpeckers in managed forests, such as characteristics of home ranges and habitat selection. Additionally, we found no studies that simultaneously related environmental factors (e.g., vegetation features, landscape composition, topography) and socio-demographic factors (e.g., productivity, population density, bird age, bird sex) to White-headed Woodpecker space use. Past studies have considered only the effects of environmental factors (specifically, the proportion of old-growth forest within home ranges) on home range size, even though socio-demographic factors such as population density and productivity affect ranging behavior in other woodpeckers. There is also a lack of regionally appropriate data on white-headed woodpecker foraging with which to guide management plans in the northwestern U.S.A. In addition to this region-specific need, no past studies have examined habitat selection by foraging white-headed woodpeckers; past studies have only measured use or selection relative to tree-level characteristics. We also could find no past studies that examined demographic consequences of foraging decisions. Our study will help answer these questions and uncover more of how this species is utilizing ponderosa pine dominated stands with a history of timber management.

Project progress:

This project was completed in 2013. The results of this study have been published in the Journal of Wildlife Management and Forest, Ecology and Management. These papers can be accessed at the links below.

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