Graduation Date
Fall 1988
Document Type
Thesis
Program
Other
Program
Master of Science
Committee Chair Name
Barry R. Noon
Committee Chair Affiliation
Cal Poly Humboldt Faculty or Staff
Second Committee Member Name
John D. Stuart
Third Committee Member Name
Hared Verber
Keywords
x
Abstract
I studied the cavity-nesting bird guild of an oak woodland habitat in the western foothills of the Sierra Nevada. Two different aspects of the biology of these birds were investigated and 2 different approaches employed. First, an experimental approach was employed to test the hypothesis that secondary cavity-nesting bird breeding density vas limited by nest site availability. A treatment and control plot were censused before and after blocking about 38% of the cavities found on the treatment plot. Nest success was also monitored for many of the nests. Total secondary cavity-nesting bird breeding density declined by a greater percentage on the control plot, suggesting breeding density of these birds was not being limited by nest site availability prior to the experiment. Comparison of indices of reproductive success between plots during the treatment year suggests reproductive success was not substantially affected by nest site reduction. A follow-up experiment on the same plots in which nest site availability was reduced by about 60% also failed to produce any detectable adverse effect on overall secondary cavity-nesting bird breeding density. Second, a comparative approach was employed to study the habitat use patterns of the species comprising this guild. I compared habitat characteristics of nest trees and sites (area surrounding nest trees) with habitat characteristics of randomly located non-nest trees and sites, and compared nest cavity, tree, and site characteristics among species. Nest trees differed markedly from non-nest trees, but nest sites differed little from non-nest sites. Nest trees had greater diameters at breast height, more wounds, more broken-off limbs, and greater dead limb lengths suggesting they were older and more decayed than non-nest trees. Snags however were unimportant as nest substrates. Nests were clearly associated with wood decay; approximately one-third of the secondary cavity-nesting bird nests found were in cavities formed by the decay process, and the majority (79%) of acorn woodpecker nest cavities were located i n either dead limbs or in live limbs next to wounds. About half of the 277 secondary cavity-nesting bird nests found were in cavities excavated by acorn woodpeckers, indicating the importance of this species within the cavity-nesting bird guild. Comparison of nest tree and site characteristics among species revealed considerable overlap. Analyses suggest that species responded to different habitat features at different spatial scales when selecting nest locations.
Recommended Citation
Waters, Jeffrey R., "Population and Habitat Characteristics of Cavity-Nesting Birds in a California Oak Woodland" (1988). Cal Poly Humboldt theses and projects. 2637.
https://digitalcommons.humboldt.edu/etd/2637