During the past decade, an increasing number of winegrape growers in California’s North Coast have placed songbird nest boxes in their vineyards. However, until recently, no studies have systematically analyzed the role of these cavity-nesting birds in suppressing vineyard pests.

The objective of a recently concluded study was to test whether biocontrol of pests is enhanced through conservation of insect-eating birds via the establishment of songbird nest boxes. Two certified organic vineyards chosen for this experiment were located in Mendocino County, California, in Hopland and near Ukiah. Both were planted between 1985 and 1988 and managed identically by the same manager, David Koball, of Fetzer Vineyards. 

David Koball was consulted so that vineyard experiments did not interfere with daily management practices. Nest boxes were erected and placed back-to-back in pairs within nest box treatments to maximize bird densities. Nest boxes were constructed from redwood following recommendations of the North American Bluebird Society. 

Project investigator Julie Jedlicka, who hand-built the 200 or so nest boxes that were installed at Fetzer Vineyards for this project, said what was most gratifying was the response of the birds once the boxes were set in place. The nest boxes increased the abundance of insectivorous birds, most notably the Western Bluebird and significant predatory effects of the blue birds were noted not only immediately adjacent to occupied nest boxes but at randomly selected points throughout the nest box treatment of the vineyard. The study revealed that the presence of occupied nest boxes benefitted the vineyard and provided ecosystem services to the winegrape growers.

As a "thank you" to Fetzer Vineyards for their cooperation in this project, Jedlicka  donated the boxes for their continued use in the vineyard. David Koball of Fetzer Vineyards, who worked closely with Jedlicka on the study, was glad to have the nest boxes in the vineyard. “From my standpoint," remarked  Koball, " there are more birds in the field, which is rewarding from a conservation perspective."

Still, the presence of birds has not replaced the need for use of organic materials to help manage the insect pressure. Koball says he hopes that further systems research will help vineyard producers implement multiple biocontrol strategies for pest management.