Use of Hardwood Tree Species by Birds Nesting in Ponderosa Pine Forests

Abstract

We examined the use of hardwood tree species for nesting by bird species breeding in ponderosa pine (Pinus ponderosa) forests in the Sierra National Forest, California. From 1995 through 2002, we located 668 nests of 36 bird species nesting in trees and snags on four 60-ha study sites. Two-thirds of all species nesting in trees or snags used hardwoods for nesting, with 19 species using California black oaks (Quercus kelloggii) and 11 using canyon live oaks (Quercus chrysolepsis). Although hardwoods comprised only 17 percent of available trees, 51 percent of nests in trees were in hardwoods. The two oak species comprised more than 90 percent of the hardwoods used. Oaks used for nesting were larger than those available. Hardwood snags were seldom used. Cavity nesters used mostly conifers, especially conifer snags, but when nesting in hardwoods they nested mostly in dead portions of live trees. Of 10 species with adequate sample sizes to examine individually, six species used hardwoods more than expected [Anna's Hummingbird (Calypte anna), Western Wood-Pewee (Contopus sordidulus), Cassin's Vireo (Vireo cassinii), Hutton's Vireo (Vireo huttoni), American Robin (Turdus migratorius) and Black-headed Grosbeak (Pheucticus melanocephalus)]. Two species used conifers more than expected [Western Tanager (Piranga ludoviciana) and Purple Finch (Carpodacus purpureus)], and two species showed no overall preference compared to available trees [Hammond's flycatcher (Empidonax hammondii) and Steller's Jay (Cyanocitta stelleri)]. Western Wood-Pewees and Cassin's Vireos nested primarily in California black oaks. Hutton's Vireos, American Robins, and Black-headed Grosbeaks showed a preference for nesting in canyon live oaks. Anna's Hummingbirds used both oak species. Our results underscore the importance of hardwood trees species, particularly oaks, to birds breeding in ponderosa pine forests. For recruitment to mature trees, these shade-intolerant species need openings in the understory that were probably created primarily by fire in the past. We recommend retention of mature oaks in ponderosa pine stands, creation of openings to encourage growth of existing oaks, and management activities that encourage recruitment of oaks to replace those that die, such as carefully-applied prescribed fire.

Parent Publication

• Proceedings of the sixth California oak symposium: today's challenges, tomorrow's opportunities

Citation

Purcell, Kathryn L. ; Drynan, Douglas A. 2008. Use of Hardwood Tree Species by Birds Nesting in Ponderosa Pine Forests. In: Merenlender, Adina; McCreary, Douglas; Purcell, Kathryn L., tech. eds. 2008. Proceedings of the sixth California oak symposium: today's challenges, tomorrow's opportunities. Gen. Tech. Rep. PSW-GTR-217. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: pp. 417-431.