What a hoot! California vineyards halt use of toxic chemicals to protect grapes in favor of nesting owls

October 25, 2021

Napa Valley vintners are increasingly turning toward winged-laborers for their pest control—and away from super toxic pesticides that poison everything, including their wine, Good News Network reports.

Barn owls, in particular, but also hawks and other birds of prey, known as raptors, are being welcomed onto vineyards across California for their skill in rat-catching, vole-estation, and gopher-gobbling—and scientists studying the impact of these strategies are finding encouraging results.

For years, vintners in California were proud of the certain je ne sais quoi, inherent in their wines, which made Napa a world class destination for growing grapes.

But, they were using super-toxic “rodent-icides,” a type of poison used to kill the mice and voles that munch on vines. The poison had become an industry standard in the state up until the 1980s; when raptors, trapping, and other more holistic methods became more popular.

According to the environmental nonprofit, Napa Green, a trend toward chemical-free farming statewide is reflected in the threefold increase of organic winegrape acreage since 2005—with the number of organic acres doubling in just the last decade.

The organization says, “Napa Green Vineyard certification provides a pathway for growers to improve soil health; become carbon neutral to negative within six to nine years; and increase the resilience of vineyards, businesses, and our community.

One of the world’s most efficient pest controllers is the barn owl, which is found on six out of seven continents worldwide and is capable of eating 3,400 rodents each year.

Matt Johnson is a wildlife professor at Humboldt State University who began a program years ago to study raptor pest control in vineyards and research the results. One of his surveys found that, of 75 California wine makers, 80% purposely invite owls onto their property by constructing nest boxes.

“We’re working mainly in Napa Valley, where there are over 300 barn owl nest boxes,” Johnson wrote on his department’s webpage.

“You can literally put a barn owl nest box in the exact location where you think you have a problem with the small mammals, and voilà! The owls will start using that area,” John C. Robinson, a local ornithologist, told Bay Nature Magazine.

Johnson and his graduate students have found that barn owls like their boxes to sit about 9 feet off the ground, face away from the sun, adjacent to an unkempt field, and preferably far from forested acres.

Research contact: @goodnewsnetwork

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