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Put a Bird on It

New research reveals birds' beneficial impact on Napa Valley vineyards



Julie Johnson delights in pointing out bluebirds whenever one alights in her certified organic Napa Valley vineyard. To encourage the colorful avians to stick around, she's put up more than 20 nest boxes, and she instructs her vineyard workers to recognize and spare the nests of other songbirds when they are working in the vines.

"People get excited about seeing these birds do good things," says Johnson, who owns Tres Sabores winery in St. Helena.

The good these birds are doing in this and the scores of other organic and sustainable winery operations that have installed nest boxes for them, however, has until recently remained somewhat anecdotal.

Johnson has also placed several nest boxes for owls at Tres Sabores. The nearly ubiquitous owl box mounted high on a pole almost functions like a totem these days; on many a vineyard tour, the guide will point to these boxes as evidence of the winery's environmentally friendly bona fides—be they certified organic, sustainable or merely well-intentioned.

"They're like superstars of the vineyard," Johnson says of the owls. "We know that barn owls are among our nighttime predators that are really crucial for vineyards, capable of eating an incredible amount of rodent pests."

But vineyard operators like Johnson can't say for sure whether the owls are performing their superstar feats in their own vineyard, whether a vineyard is even a particularly good place to site the nest, from the owl's point of view, or if they're simply talking from their tail feathers. And while no cynic might tag a box for pretty songbirds or majestic owls with the term greenwashing, "feather dusting" does have a ring to it.

To answer questions about the efficacy of owl boxes, graduate student researchers from Humboldt State University have begun a first-of-its-kind study, painstakingly mapping the interaction between owls and vineyard habitat in the Napa Valley.

"Finally, we're starting to get some really great research," says Johnson, who hopes that the findings will help her to develop a program for "bird-friendly" farming or wine, similar to Fish Friendly Farming, based in Napa, and the Smithsonian Migratory Bird Center's bird-friendly coffee program.

"They are very interested in looking at vineyards," Johnson says of the Smithsonian, "because similar habitat exists here. The idea is that these beneficial birds can coexist quite nicely." But first, research is needed to quantify that idea. "We know what the research needs to look like," says Johnson, "we just need to take it to the next step."


Under the shade of the oaks at Tres Sabores last summer, Carrie Wendt takes a break from that very research to explain the owl study she began in February. A graduate student pursuing a masters degree in natural resources and wildlife at Humboldt State University, Wendt studies the ecosystem services that wildlife can provide in agricultural systems. Her advisor, Dr. Matthew Johnson, instigated the project by pointing out that, although owl boxes have been used in vineyards for several decades, there is little to no scientific literature about them. Many of the oft-cited statistics on owls come from studies done in England and elsewhere.

To start, Wendt cold-called hundreds of vineyard managers up and down Napa Valley for permission to monitor their owl boxes. With a list of nearly 300 boxes in hand, she visited them all three times at 10-day intervals.

"It took five days to check all 300 at first," Wendt says, adding, "I've driven over 10,000 miles this year already!"

DEATH FROM ABOVE Humboldt State University researcher Carrie Wendt is studying the impact of owls on vineyard rodents in the Napa Valley.
  • DEATH FROM ABOVE Humboldt State University researcher Carrie Wendt is studying the impact of owls on vineyard rodents in the Napa Valley.

But only one-third of those boxes attracted a pair of breeding owls, so Wendt next concentrated on 91 boxes that did, 69 of which produced at least one chick that year. She's at Tres Sabores to check up on three chicks that are almost ready to fledge and begin exploring the world outside.

After a short hike to the box, Wendt hands her laptop to her undergraduate assistant, Breanne Allison, and plugs her improvised owl cam into the computer. Commandeered from a digital overhead projector, the camera is taped, with a flashlight, to a telescoping pole.

Wendt carefully pokes the camera into the owl box, while Allison monitors the screen. "You see those feathers right there?" Allison says. "Oh, no," Wendt replies. "Dammit. That's a dead chick."

It's not a happy introduction to their work, but they reluctantly tilt the screen for me to view. Inside the box is a wasted scene. Crumpled heaps of feathers lay scattered about—it's a failed nest.

"That's really unfortunate," says Wendt. "I'm sorry. Total downer!"

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