Bird Communities of the Garry Oak Habitat in Southwestern British Columbia

Abstract

Identifying the bird communities of a habitat could contribute to conservation efforts and provide benchmarks for ecosystem studies. Garry Oak (Quercus garryana) ecosystems in British Columbia are among the most endangered in Canada and warrant conservation. Four bird communities were determined by analyzing an extensive sample of Garry Oak habitat bird data. These communities were defined objectively by aggregations of the bird species themselves from across the various sites and areas. Characteristic species of these communities include American Goldfinch (Carduelis tristis), Spotted Towhee (Pipilo maculatus), Bewick’s Wren (Thryomanes bewickii), Rufous Hummingbird (Selasphorus rufus) and Chestnut-backed Chickadee (Poecile rufescens) in community 1; House Wren (Troglodytes aedon), Olive-sided Flycatcher (Contopus cooperi), Purple Finch (Carpodacus purpureus), White-crowned Sparrow (Zonotrichia leucophrys), and Pine Siskin (Carduelis pinus) in community 2; Western Tanager (Piranga ludoviciana),Yellow-rumped Warbler (Dendroica coronata), American Goldfinch, Pine Siskin, Pacific-slope Flycatcher (Empidonax difficilis), Cassin’s Vireo (Vireo cassinii) and Chipping Sparrow (Spizella passerina) in community 3; and Northwestern Crow (Corvus caurinus) and European Starling (Sturnus vulgaris) in community 4. Differences between the communities are suggested from the life history traits of the species, including a community consisting mostly of insectivores when on breeding territory (number 1), one with species foraging primarily in shrubs and trees (community 3), and another with tree-nesting ground gleaners (number 4). One community (number 3) had analogues in two widely disparate areas: oak-associated in north-central New Mexico, and aspen (Populus tremuloides)-related in northcentral British Columbia; otherwise communities reported in the literature were generally not directly comparable.