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News / Life / Pets & Wildlife

How one Napa vineyard might have saved millions of dollars by using birds as pest control

By Jason Mastrodonato, The Mercury News
Published: November 13, 2023, 6:00am

NAPA, California — On a damp and gray Friday at Bouchaine Vineyards, Rebecca Rosen looked up, noticed the handful of ravens circling above her and lobbed an insult.

“Jerks!” she yelled.

They flew together, swirling and squawking as she walked to the trunk of her Tesla Model S and pulled out the box.

There, she hides her ammo: a 6-year-old Harris’ hawk named Rocky, a 17-year-old falcon named E.B. and a 4-year-old spectacled owl named Hootbert, whose only job is to perch himself on a chair and let some tipsy wine tasters snap a photo.

Rocky is the real threat. Rosen pulled him out of the box, removed his hood and loosened his strap. Free at last, Rocky soared to the roof of the Bouchaine tasting room and perched high enough to scan the vineyard. His mere existence is enough to irritate the ravens.

Armed with long legs, a wingspan of almost 4 feet and an air of unspeakable confidence, Rocky has an aura that demands respect. The raven family knows it; they met one of Rocky’s siblings just last week, when the bird chased the ravens out of a tree at nearby Stanley Ranch.

On this particular spring day, Rocky wasn’t hunting. He was at Bouchaine as part of a weekly falconry demonstration, a fun attraction open to the public and, more importantly, a stoic symbol of what was soon to come: another summer at the vineyard, where Rosen’s hawks and falcons will work the fields, shooing away pesky house finches, red-winged blackbirds, cowbirds and starlings hoping to feast on millions of dollars worth of grapes.

“I like to start at the end of a lag season, which varies year by year, but is usually the end of June or early July, before the pinot grapes start to color up,” said Rosen, an Arizona falconer who moved to Napa a few years ago as business picked up. “It takes about two weeks to change the behavior patterns of birds. It’s easier to get birds out when there’s nothing to eat than to get them out after they’ve started eating.”

Rosen owns 20 different birds, mostly falcons and hawks, which she deploys strategically, depending on the job.

Hawks are typically reserved for the work that requires the most grit. They’ll often catch their prey, but they make for bad abatement birds, because they’ll get bored — or literally fed up after eating — and basically start sleeping on the job.

Falcons are the bird of choice for most vineyard gigs. Rosen has a handful, including a peregrine falcon, the fastest animal on the planet. The bird can dive at speeds upwards of 200 mph.

“These birds are like projectiles,” Rosen said. “Like a projectile, they don’t need to be big, they just need to be fast and hit in just the right spot. That’s why the (fear) response to a falcon is so strong. They’re like the shark fin in the water.”

Mostly, though, Rocky and his friends are there to fly above the vineyard, intimidate the grape-eating birds and send them somewhere else.

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In Napa, falcons are nature’s pesticide. They’re a potent force.

It’s called “a landscape of fear effect,” said Sara Foss, a senior lecturer at the University of Canterbury in New Zealand. “When a predator is present, the prey will behave differently. They spend less time gorging themselves and have to be careful.”

Foss ran a study in 2013 that reintroduced the New Zealand falcon into native habitats where European birds were running amok with few predators to control them. The results for the local vineyards were remarkable: Grape damage was reduced by nearly 70 percent.

Wild raptors can be spotted in the skies above Napa, but trained birds like Rosen’s can play a big role, too.

“The trained birds can be effective,” Foss said. “And maintaining those wild populations or supporting them will keep the pest species at a lower level.”

Bouchaine president Chris Kajani has not totaled up exactly how many grapes have been saved by Rosen’s falcons over the years, but she knows it’s a big number.

Kajani met Rosen in late 2015, just as Bouchaine was preparing for a late harvest of chardonnay grapes. Over the course of 48 hours, a flock of birds came through and “took every berry off the vine,” Kajani said. “There was nothing left.”

Rosen has worked for the winery ever since. It’s one of several Napa vineyards she counts as clients, charging anywhere from $400 to $1,500 a day, depending on the difficulty of the job. It might seem expensive, but not once Kajani starts doing the math.

“We do somewhere around 200, 250 tons of grapes,” she says. “Let’s say we (lose)10 percent. That’s 25 tons, 165 gallons a ton, about 2.4 gallons a case, over 1,700 cases that we don’t make. If our average case price is around $500, that’s $859,000 (per year).”

Rosen nearly fell over.

“I should be charging more!” she said.

Bouchaine prides itself on running an eco-friendly operation, but how it thrived without falcons is a mystery to Kajani. The 87-acre plot is bordered by rows of telephone poles that run down the long sides of the land. Before the falcons arrived, flocks upon flocks of birds would perch atop the telephone wires, she said, just waiting for the grapes to ripen so they could dive in and eat their fill.

But the use of falconry at vineyards isn’t as widespread as one might think — or hope, said Aaron Fishleder, vice president at Cakebread Cellars, another Rosen client.

“There’s a lot of other technology,” Fishleder said. “But some of it is causing consternation and issues with the community around the vineyards.”

Among those other methods, cannon fire — yes, cannon fire — doesn’t work. The marauding birds get so comfortable with it, they go right back to their feeding spot when the sound dissipates. The flimsy, metallic pieces of tape that are supposed to scare birds away? They’re a joke at this point. Netting can be helpful, but birds will often find an opening near the bottom, then get trapped inside.

“The falcons are great, because they don’t make loud noises,” Fishleder said. “Nobody traps birds. They aren’t shiny pieces of tape. They’re just natural birds, flying around and doing what they’re doing.”

The movement toward more environmental winemaking isn’t just some eco trend or branding thing, said CalPoly Humboldt wildlife professor Matthew Johnson, who studies birds in vineyard settings.

Studies in the 1990s found that it was actually less expensive to go organic with wine grapes than to use pesticides or rodenticides, adding financial incentive to what was already a groundswell of support for green solutions. “A lot of the really high-end, elite grape growers are going organic,” Johnson said.

Falcons alone can’t save vineyards. But they’re a part of a larger ecosystem that can function naturally if given the chance.

Back in the ‘80s, a lot of growers began installing nest boxes to entice barn owls to make a home among the vineyards. Owls eat the voles, mice and gophers that are prevalent in Napa, and while the rodents don’t eat the grapes, they chew the stalks and damage the vines.

“We’ve calculated on average a full family of barn owls — adults plus three or four offspring — will eat about 3,400 rodents in the course of a year,” said Johnson, who studies barn owls at 65 different Napa vineyards. “Some of these vineyards will have 10, 20, even 30 nest boxes. So you’re talking about 100,000 rodents removed. It’s pretty remarkable.”

If the falcons and hawks are scaring away the grape-eating birds, and the owls are eating the vine- and stalk-damaging rodents, what remains to be done?

“We are studying — for the first time — the bluebird and swallow boxes,” Johnson said.

Why would a vineyard want to attract more birds? Because bluebirds and swallows don’t binge-eat grapes by the flockload. But they do eat insects.

“Birds aren’t necessarily a bad thing,” said Rosen. “You just have to decide. Yes, bluebirds eat grapes, too. But they tend to operate in pairs or small groups. They don’t come in a plague of 2,000 and wipe out your vineyard.

“So it’s up to the individual vineyard manager to decide at what point are birds a problem. Because they’re a part of the ecosystem. And nature loves balance.”