Resource partitioning by an avian guild in an oak woodland

Graduation Date

1988

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, 1988

Committee Chair Name

Barry R. Noon

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Birds--Behavior, Birds--Feeding and feeds, Bird populations, Humboldt State University -- Theses -- Wildlife Management

Abstract

Bird community structure was described in an oak woodland near Hopland, Mendocino County, California, between March 1986 and June 1987. The bird community was censused, the vegetative community was measured, and the foraging behavior of 20 insectivorous and/or granivorous bird species was observed on 23 5 ha study plots. Resource partitioning between bird species in the foliage-foraging guild was investigated. Seventy-three bird species were detected during censuses. Thirty-three species were insectivorous and confirmed breeders. Cavity nesters comprised a large proportion of the breeding bird community in terms of species (24.5 percent) and individuals (58.1 percent). Deciduous oak trees dominated most study plots, and blue oak was the most abundant deciduous oak. Floristics, structure, and elevation varied among study plots. The 800 m elevation gradient that existed among study plots was partially responsible for the variance in vegetative characteristics among plots. Three guilds (bark-, ground-, and foliage-foragers) were delineated based on frequency of use of substrates where foraging attempts were directed. The foliage-foraging guild consisted of 10 species. These 10 species were widespread, with an average of 90 percent frequency of occurrence across study plots. Year-round residents (three species) appeared to be more abundant than summer residents (seven species). Resource partitioning between bird species in the foliage-foraging guild occurred on both spatial and behavioral "axes". Spatial overlap was measured by habitat association, plant species use, and location on the plant. Behavioral overlap was measured by substrates and maneuvers used to obtain prey, search movements, and prey type. Spatial and behavioral overlap was extensive among species, but the abundance of each species and the frequency of use of resources and behaviors varied between species. All species differed significantly on one or more resource axes. The influence of residency, body size, and nest type on resource use is discussed.

https://scholarworks.calstate.edu/concern/theses/vm40xv10k

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