During the vineyard expansion on the California central and north coasts the past decade, many growers left individual trees within newly established vineyards. Recent research in several habitat types worldwide has documented the ecological contributions of lone or residual trees to habitat structure, connectivity, and aesthetics in the highly-modified landscape. During spring, 2008, we used point counts and behavioral observations to compare bird diversity and abundances from three replicate vineyards at 17 valley oak (Quercus lobata) trees within the vineyards vs. 17 valley oaks of similar size in adjacent oak savanna. Our measurements of bird species diversity and abundances were similar in both treatments, including on those of several insectivorous bird species potentially beneficial to growers. Several bird species, however, that may be sensitive to development were detected substantially more in savanna or were unique to savanna. To further evaluate the costs to the grower and the contribution to biodiversity of lone trees in the vineyard landscape, we are using the results of this pilot study to develop an expanded study, including more replication, a measure of bird reproductive fitness, experimental habitat enhancement, and cost-benefit analyses.
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