Winemaking is a delicate and millennia-old craft. To achieve a desirable product, vintners have to pay close attention to soil, rain, heat, and sunlight. Mice and gophers are other problems that vintners often turn to rodenticides to solve. In a bid to provide a more natural solution, a team of students at Humboldt State University in California is testing the efficacy of a centuries-old practice: using owls to hunt pesky rodents.

As part of the long-term study, the researchers placed around 300 owl nest boxes in random places through vineyards in Napa Valley. The aim of the study is to test how effective owls are at removing pests and if they can offer a feasible natural alternative to pesticides.

The students surveyed a total of 75 wineries in Napa Valley, 80 percent of which have reported a difference in rodent control since they started using the owl nest boxes. During the nesting season — which is around four months — barn owls spend about one-third of their time hunting in the fields. On average, a family of barn owls eats about 1,000 rodents during the nesting season.

So far, the study has revealed that the owls were doing a pretty good job at reducing the number of gophers in vineyards, while the number of mice hasn’t been affected. With that said, the key part of the study is whether the owls are leading to a decrease in rodenticide use in Napa Valley. According to the researchers, that is indeed the case, with most of the participating vintners reporting using no poison since they introduced the owl next boxes.