PARENT SESSION
Oral Session 2: Avian Ecology I: Habitat and Disturbance.
Presiding: D Miles and C Lepczyk
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room A 106.
Do stand structure changes resulting from "sudden oak death" affect insectivorous, cavity-nesting birds?
Apigian, Kyle*,1, Dahlsten, Donald1, Brown, Letty1, Allen-Diaz, Barbara1, 1 University of California - Berkeley, Berkeley, CA
ABSTRACT- Sudden Oak Death (SOD) is a tree disease caused by a newly described pathogen, Phytopthora ramorum. The disease affects dozens of plant species, and its effects are particularly pronounced in coast live oak (Quercus agrifolia), often resulting in rapid crown dieback and tree death. The disease has killed thousands of trees in 12 California counties. Such disease-induced habitat changes may impact bird populations by altering their resource base. For example, forest dieback can result in changes to insect populations, which subsequently impact insectivorous birds by forcing them to switch prey items, change foraging substrates, or increase foraging time. This can ultimately impact the nesting success of these birds. The goal of this study is to examine the effects of SOD-induced changes in oak woodlands on insectivorous cavity-nesting birds, particularly oak titmice (Baeolophus inornatus) and chestnut-backed chickadees (Poecile rufescens). We are examining the impacts of SOD on the population ecology of these birds by studying nest box use, as well as the behavioral ecology by studying foraging behavior and diet composition. We set up study plots in the San Francisco Bay area in both heavily affected stands (high rate of SOD symptoms and many dead trees) and lightly affected stands. Preliminary data indicates that nest box use may be higher in heavily affected stands than lightly affected stands. Our foraging data indicates that coast live oak is a preferred foraging substrate for chickadees, while California bay-laurel (Ubellularia californica) is avoided more than expected. Also, in heavily affected stands, birds tend to switch to a variety of other trees and shrubs as foraging substrates, rather than feed more heavily on remaining oaks or bays. We suggest that any management related to sudden oak death recognizes the importance of protecting healthy coast live oaks while promoting diverse stands in affected areas.
Key words: foraging, baeolophus inornatus, disturbance, poecile rufescens