Wine Country Pest Control: Bring in the Owls

Wine Country Pest Control: Bring in the Owls

We tend to think of vineyards as pristine places, with row upon row of well-tamed green vines and picture-perfect clusters of grapes becoming ripe enough to be crushed, bottled, labeled and, ultimately, poured into wineglasses and enjoyed.

Of course, vineyards are all that and more. And although winegrape growers might farm a more refined product than do many other stewards of agricultural land, they still have to deal with a problem common to all cropland the world over: pests. And by pests, we mean rodents. 

However, wine country pest control looks a little different than it does on your average farm. The next time you cruise through California wine country—either in person or online—take a look about 10 feet up in the air and you might see them interspersed at regular intervals among the grapevines: owl boxes for rodent control.

Vineyard Pest Control: A Short History

Unlike so many things having to do with winemaking, the use of owls for rodent control is not a matter of tradition. Instead, the building of owl boxes in Sonoma County and the Napa Valley came about through sheer necessity. 

The abbreviated version of that history is as follows: Rodents have presented a problem for crop-growers for as long as cultivated farming has existed. Until fairly recently, in California wine country winegrape growers controlled rodents the same way farmers everywhere have done: by dumping enough commercial pesticide to keep their populations in check.

We're pretty sure you can guess what happened next.

Grapes are a sensitive crop in which the subtle nuances of the taste of the end product is everything. Monoculture, combined with overuse of both pesticides and fertilizers, began to affect the flavor of the wines made by California vintners—after all, no one wants to sip a buttery Chardonnay and taste notes of pesticide. Sometime around the 1980s, when they were looking to employ a more natural solution to the rodent problem, winegrape growers decided to enlist the talents and appetites of owls for rodent control.

The Owl Boxes of Northern California

It's worth noting that the use of owl boxes for rodent control does have some precedent worldwide. According to Bay Nature Magazine, Malaysian farmers have built barn owl nest boxes on palm oil plantations, Kenyan maize farmers have done the same, and Israel enacted a national program that has seen some 1,500 nest boxes placed in agricultural fields. In the United States, farmers have turned more and more to the kind of natural pest control that only our owl friends can provide.

Owing to legislative changes as well as an overall trend toward sustainability, more and more vineyards are building owl boxes for rodent control. That same Bay Nature Magazine piece says that in a survey of 75 vintners, 80 percent of them say that they use barn owls as part of their overall vineyard pest control strategy. As well, a group of researchers—who weigh, measure, photograph and band each owl—are closely monitoring 280 nest boxes at 65 vineyards that are owned and managed by different groups. The owl rodent-control program is widespread and continues to grow.

Owls for Rodent Control: Does It Work?

The question of whether building owl boxes for rodent control is effective is more than just the subject of research studies. Wine country pest control is serious business with crop yield—and the millions of dollars that those crops bring in—at stake. So are the owl boxes of Northern California really making a difference to the health and well-being of the vineyards?

The answer is, well, maybe. Probably. Somewhat.

Some hard facts have emerged from the owl rodent-control program: First, owls are gopher-gobbling machines. According to researchers, barn owls spend only their nesting season in their vineyard owl boxes, and of those four months, they spend a third of their time hunting in the vineyards. During that window, a single barn owl family eats an estimated 1,000 rodents. Another study says an owl family eats 3,400 rodents annually. So if an owl family decided to hang out year-round, and a farmer had, say, 10 owl boxes, that's nearly 35,000 rodents removed from the vineyard. 

While the numbers owls are putting up are impressive, it still doesn't answer the question as to whether a vineyard pest control plan that involves owls is effective.

The truth is there's no real way to know. What is known is that farmers who use owl boxes for rodent control use less rodenticide overall than those who don't. And given the damage pesticide use does not only to plant life, but also to other animals in a particular area or ecosystem, a solution in which growers work with nature instead of against it can be considered a win. 

So the next time you pour yourself a glass of wine from Northern California, toast the owls who helped make it possible.

To find out more about the use of owl boxes for rodent control, including how it affects the owls and how researchers study them, see Bay Nature Magazine

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