In California Vineyards, Owls are Replacing Toxic Chemicals to Help Protect Vines

Clusters of wine grapes are on the vine ready for harvest in Napa Valley.
About 80 percent of the winegrape growers in California are now using barn owl nest boxes in order to reduce the rodent population in their fields. (Image: Michael Warwick via Dreamstime)

Wine cultivated in the top California vineyards tastes excellent, beyond doubt. However, have you ever thought about who or what safeguards the vineyards from rodents and pests? The winemakers are particular about each aspect of the process, from cultivating the grapes all the way through to production and bottling. They have to be especially careful about the rodents and pests that can wreak havoc in the vineyard, killing the plants and spoiling the fruit. Wine producers in California’s Napa Valley are now resorting to a better natural alternative to pesticides: barn owls! In order to combat the rodent population, they previously had to use pesticides. However, the side effects of using pesticides are well known.

The students of Humboldt State University have begun tracking the use of barn owls in vineyards, a practice that some vintners took up as early as the 1980s. This is actually a long-term research project led by the university’s Wildlife Department Professor Matt Johnson. The students are mainly working in Napa Valley vineyards where there are more than 300 barn owl nest boxes. 

80 percent of California vineyards now use owls to control rodents

The students have checked around 75 wineries located in California and found that 80 percent of them now use owl nest boxes. The barn owls have a four-month-long nesting season and they hunt in the fields. In a year, a barn owl family can kill approximately 3,400 rodents. Gophers, voles, and mice are the main prey of these raptors. So far, the students have seen evidence that the barn owls in those vineyards have successfully reduced the gopher, but not the mouse, population, and their data on voles is inconclusive.

In a year, a family of barn owls can kill approximately 3,400 rodents.
In a year, a barn owl family can kill approximately 3,400 rodents. (Image: Ondřej Prosický via Dreamstime)

The California Department of Pesticide Regulation imposed stricter rules on rodenticide use. These products can lead to the death of the birds and predatory mammals that feast on rodents killed by pesticides. The students have noted that a majority of the wineries that have started using barn owls no longer use toxic rodenticides.

Johnson told baynature: “Whether the use of barn owl boxes caused that reduction in rodenticides is, of course, not proven. Nonetheless, this result is encouraging.” The students have been asked to monitor 280 owl boxes set up in 65 different vineyards for the study. 

It is not a drastically new idea to use natural weapons against rodents and pests that harm the plants in vineyards. In fact, farmers have used owls and other raptors for killing rodents for ages. In the last few decades, however, usage of toxic pesticides has shot up. This has hampered the ecology to an extent and so experts think implementing a more natural way is the better option.

The Gunther's vole sitting on a rock.
Farmers have used owls and other raptors for killing rodents for ages. (Image: Lukas Blazek via Dreamstime)

The Napa Valley winegrowers are using barn owls to ensure the longevity of the plants and enhance the yield, but they are also using other tactics. The vineyard owners are also trying to reduce water usage in the fields. While using barn owls to combat rodents is a good idea, the vintners are also keen on using other prey birds like hawks and falcons. 

The advantages of using barn owls and other predatory birds for rodent and pest control are obvious. This not only helps reduce damage to the ecology, but the plants are also spared from toxic chemicals. The vineyards can also save a significant amount of money that would otherwise be spent buying pesticides.

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