Effects of elevation and forest cover on winter birds in mature forest ecosystems of southern British Columbia

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Abstract
Winter diversity, distribution, and density of nonmigratory birds were examined in six mature forest ecosystems from two study areas in southern British Columbia. Forest age ranged from 91 to 150 years and the ecosystems ranged from 500 to 2100 m above sea level. Sampled forest stands had no previous history of logging and were a minimum 30 ha in size. The main objectives of this study were to measure nonmigratory birds in relation to elevation and to percentage of stand-level lodgepole pine composition. Twenty-one nonmigratory bird species totaling 2747 observations were detected at 775 point-count stations in 107 stands using 10-min unlimited-distance point counts. Pine siskins (Carduelis pinus (Wilson, 1810)), red-breasted nuthatches (Sitta canadensis L., 1766), and red crossbills (Loxia curvirostra L., 1758) were the three most commonly detected species. Mature forests at low elevation had between 1.7 and 3.5 times more species and between 2.0 and 4.7 times more birds than forests at high elevation. In addition, species richness and bird density declined with increasing stand-level composition of lodgepole pine. We suggest that low-elevation ecosystems be given high priority in coarse-filter management of winter bird habitat.