Owls protecting vineyards

Te Waiharakeke - Rodents like gophers and mice wreak havoc on vineyards, causing owners to make drastic decisions on how to control them.

Rather than turning to rodenticides to deter pests, a new study is testing the effectiveness of owls to manage the problem.

The researchers have surveyed 75 wineries in Napa Valley, and four-fifths now use the owl nest boxes and notice a difference in rodent control.

New Zealand wineries should trial the morepork, which is the only remaining native owl species found in Aotearoa. Barn owls have only very recently colonised in New Zealand from Australia.

Winemakers must pay close attention to their soil, the rain, the heat, and the sunlight. But rodents like gophers and mice can wreak havoc on a vineyard.

Rather than turning to rodenticides to deter pests, graduate students at Humboldt State University in California are testing a more natural approach by using owls.

Researchers have placed 300 owl nest boxes sporadically through vineyards in Napa Valley. They are documenting the impact of relying on owls to deter and remove pests rather than rodenticides.

The barn owls have a four-month nesting season, during which they spend about one-third of their time hunting in the fields. A family of barn owls may eat as many as 1000 rodents during the nesting season or around 3400 in a single year.

So far, the graduate students have found that the barn owls in vineyards are reducing the number of gophers, but not mice. They are also evaluating the owls' impact on voles, but that is inconclusive at this time.

The researchers say that most of the vintners in their study no longer use the rodenticides since adding nest boxes to their properties. But whether relying on owls is reducing pesticide use in Napa Valley isn't certain.

Farmers have been using owls and other raptors to hunt rodents for centuries, but modern chemical pesticides have taken precedence over natural methods in recent times.

In an effort to leave less of a negative impact on the environment, farmers around the world are reverting back to relying on raptors to control pests, rather than toxic pesticides.  

Still, there's a long way to go in improving sustainable agriculture, including in the wine industry. Napa Valley has over 40,000 acres of vineyards, and only 3800 acres are certified organic. With the increasing use of nest boxes, there's hope that farmers will rely on these more natural methods over the rodenticides.