eWestern Birds

Effects of Natural Habitat on Pest Control in California Vineyards

Katharine A. Howard and Matthew D. Johnson

ABSTRACT: Ecosystem services provided by wildlife can offer powerful incentives for conservation, particularly if species can be linked to natural habitat. We examined the hypothesis that natural habitats adjacent to vineyards provide a source of insectivorous birds by testing the prediction that predation rates should be higher close to oak woodland than in the interior of a vineyard. We simulated an insect outbreak in four small vineyards all adjacent to oak woodland. There was no evidence that predation was higher along edges of vineyards than in the interior. We did find that birds responded quickly to a simulated outbreak of insect larvae, with predation rates during the late summer reaching 90%. Motion-sensing cameras revealed that the most common predator of the larvae was the Western Bluebird (Sialia mexicana). These results suggest that vineyard managers may take advantage of biological pest control offered by songbirds and perhaps increase control by actively managing for the birds, a potentially beneficial scenario for both vineyard managers and bird conservation.

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