Sonoma County vintners using barn owls for pest control
High above the vineyard, Michael McGuire leans from his perch on a tall orchard ladder and signals: pay dirt. He’s peering cautiously into the dark interior of a rectangular wood box bolted to the top of a 15-foot metal pole amid rows of greening grapevines.
Usually, McGuire is out making house calls as an animal exclusion specialist for Sonoma County Wildlife Rescue. He’s the person people are happy to see when skunks go wild and spray under the house, or bats move into the attic.
Today he’s on a different mission. He extends his phone slowly into the box. From inside we hear a faint hissing shriek, like a broken steam pipe. After taking a quick video, McGuire retreats, then backs quietly down the ladder. In the video, we see three big fluffy white owl chicks. They all stare round eyed at the intruder. It’s mid-spring, and the three fledglings are what we came to find. It means barn owls have moved in and are nesting here, and that means the chicks’ parents are out on the job, keeping Quail Hill Vineyard from being overrun by hungry gophers.
Quail Hill’s 10 owl nesting boxes, staked out around the vineyard, are part of a small but rising trend among local growers. Supported by partners like Wildlife Rescue’s Barn Owl Management Project (BOMP), they’re enlisting wildlife to help on the farm.
Left to itself, nature is not particularly friendly to farmers. The standard approach to starting a vineyard is to clear away the natural vegetation and wild things, then use machinery and chemicals to fight off pests and keep out any competing plants.
But for the last decade or two, an increasing number of growers have been experimenting with a more organic approach, intentionally letting plants grow between the rows of grapes. The right cover crops, it turns out, can help manage water and improve soils. Equally important, they reintroduce a diversity of life to the vineyard, from healthy microorganisms in the soil, to insect-eating spiders.
Unfortunately, the verdant strips are also a lush green welcome mat for plant-munching rodents such as gophers.
“Gophers and voles are particularly dangerous to grapevines,” says Jason Stalling, vineyard manager at Quail Hill in Sebastopol. “Gophers will chew through the base of a young vine in a single feeding session. Voles can girdle fully mature vines, if left unchecked”.
Rather than killing rodents with poison, the solution for Lynn and Anisya Fritz, Quail Hill’s owners, was to bring native wildlife back into the vineyard, as partners. That’s where the barn owls came in. By setting up specially designed nesting boxes, they hoped to encourage the raptors in the area to take up residence in the vineyard, raise a family, and in so doing, help manage the rodents.
As Wildlife Rescue McGuire’s ladder-top survey confirmed this April, it’s working. Quail Hill now contracts the Barn Owl Management Project to inspect, maintain and seasonally clean their owl boxes.
Around Sonoma County, a growing number of property owners are following suit. Hundreds, perhaps thousands of barn owl nesting boxes are now sitting on poles around the county.
Although barn owls are native to Sonoma County, few people ever see them, because they’re usually only out at night, and work in the dark. They’re a gloriously handsome bird, with soft rust and white mottled feathers, long silent wings, dark round eyes and a finely sculpted ruff around the face. Their main diet are the rodents that come out to graze after the sun sets.
To their prey, the first and last view of a barn owl is usually an oval basket of eight very sharp talons dropping silently from the night sky. The owls are remarkably good hunters, thanks to some impressive accessories, according to Dr. Matt Johnson, a Humboldt State University Wildlife scientist, who’s leading a first-ever study of their role in Wine Country vineyards.
They have amazing hearing, for example. “In studies,” Johnson says, “scientists found barn owls were able to locate and snatch prey in total darkness, relying just on sound.” It turns out, the characteristic mask around the owl’s face isn’t just for looks. “Those facial feathers actually channel and concentrate sound toward the owl’s ears, which are located at the edges of the ruff on either side.” The feathers work something like cupping hands behind our ears.
But do barn owls help Sonoma County vineyards and farmers? Surprisingly, no one had studied whether owl boxes were actually working. Johnson and his team are systematically studying them to find out.
“In the beginning I was skeptical,” he admits. “But when we did our surveys, we found that 25-50% of the owl boxes were occupied.”