A “Bird’s-Eye-View” of Oak Woodland Conservation

A Collaborative Venture by California Partners in Flight

Oaks ‘n’ Folks – Volume 12, Issue 2 – September, 1997

For most Californians, oak woodlands and their wildlife are a familiar and emblematic natural setting. Looking over rolling foothills of oaks would hardly conjure up images of conservation urgency and imminent decline for many people. Yet a clearly “cryptic” conservation crisis exists for woodlands and their wildlife in California. Many oak species are not regenerating sufficiently and many grasses and other flowering plants under these trees are invasive weeds.

The birds of our California oaks, species that consume and store the acorns, nest in the tree cavities, and otherwise depend on the oaks, therefore, are also at risk. How this issue and how birds might indicate particular concerns in oak woodlands, is the concern of “California Partners in Flight” (CPIF). CPIF is the basis of our developing “Oak Woodland Bird Conservation Plan: A strategy for Restoring the Oak Woodland Habitats in California associated with them.” California Partners in Flight was formed in1 1992 with the full participation of state, federal and private land managers, scientists and researchers interested in the conservation of nongame land birds.

Recognizing that the major cause of population declines in California was habitat loss, CPIF began identifying critical habitats important to birds. Our first effort was on riparian habitat (see the “Riparian Bird Conservation Plan on the PRBO web site http://www.prbo.org/prbo, for current information. Our second major effort is with birds in oak woodlands.

The objective in developing an oak woodland bird conservation plan is to synthesize and summarize the current state of knowledge concerning the requirements of birds in oak woodland habitats. Then provide recommendations for habitat protection, restoration, management, monitoring and policy to ensure the long-term persistence of both the birds and their critical habitat. Key to this process is a series of “species accounts” that provide detailed information on selected bird species of oak woodlands and their ecology, distribution and conservation concerns. Species we selected include the acorn woodpecker, blue-gray gnatcatcher, lark sparrow, oak titmouse, western bluebird, western scrub jay and the yellow-billed magpie. These species were chosen to represent a diversity of ecological interactions and conservation issues in oak woodland habitat that, as a whole, help indicate and focus management and conservation concerns.

The importance of acorns to wildlife cannot be overestimated. Among birds, the acorn woodpecker and western scrub jay clearly center much of their yearlong foraging activity on the consumption and storage of acorns. Large trees provide the most acorns, and thus the preservation of our remaining large oaks, particularly the imperiled valley oaks, is of great concern. Among these birds, the western scrub jay is important to oaks for the dispersion of its acorns. These jays cache thousands of acorns throughout oak woodland habitat. Because they do not retrieve the entire cache, remaining acorns can sprout and grow.

Many oak species are not regenerating over much of their range. The reasons for this are complicated and inter-related. Fire suppression, intensive grazing by cattle, invasion by weedy annual grasses, and other factors have conspired to reduce oak regeneration in many regions of California. This is the “cryptic” crisis: most oaks we see across our landscapes are very old. As these trees continue to age and senesce, increasingly no younger cohort, or, age group of trees is present to replace them. Unless we can manage our oak woodlands (the majority of which are in private ownership) to facilitate oak reproduction and recruitment, we may slowly, but surely lose these great landscapes.

Large oak trees are mosaics of living and dead branches. Large oak trees are key to the nesting of most oak woodland birds. Woodpeckers drill cavities into the heart rot of dead branches and create nesting and roosting sites. Disused cavities become the homes for other cavity-nesting species. Thus, acorn woodpeckers, Lewis’ woodpeckers, northern flickers, and Nuttall’s woodpeckers create cavities that may eventually be used by wood ducks, pygmy owls, ash-throated flycatchers, oak titmice, white-breasted nuthatches, Bewick’s wrens, western bluebirds, and, unfortunately, the introduced and very aggressive European starling. This latter species out competes several native species for cavities, particularly the western bluebird, and so is a factor in bluebird decline statewide. In addition, many species like red-shouldered hawks, western scrub jays, and yellow-billed magpies and others place their nests in oaks.

Finally, some birds are uniquely Californian. Oak titmice and yellow-billed magpies occur only in California. Other oak woodland species like Nuttall’s woodpeckers, California thrashers, and California towhees are found almost exclusively in California and provide a compelling reason for heightened conservation concern. Clearly, most of those birds most peculiar to California are tied to its most distinctive landscape.

We at CPIF are bringing this information together to provide our best “bird’s-eye-view” of oak woodland habitat, its management, and conservation concerns. Our next steps will include efforts to engage in collaborative research to identify key links between the bird community and healthy oak woodland ecosystems, and to assist in the implementation of progressive management alternatives that instill regeneration of oaks in woodlands on private land. Our hope is that this information will complement the efforts of the IHRMP, California Oak Foundation, and others to help conserve and restore our great oak woodland landscapes.

prepared and edited by Richard B. Standiford, Justin Vreeland, and Bill Tietje