An Island Scrub-Jay cooperates with scientists aiming to restore habitat on recently burned land on Santa Cruz Island. Photo: Morgan Heim

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These Students Are Partnering With Corvids to Replant a Forest After Fire

Island Scrub-Jays are acorn-planting machines. Might flying foresters be just what today's scorched Western landscapes need?

The bird flares blue as gas flame. It seems to dive, not fly: Two flaps, a tuck tilting to full fall, all grace and faith and then the sure catch of its wings rocketing it up, before another plunge lands it swaying on a branch.

It’s an Island Scrub-Jay, cousin of the California Scrub-Jays common at mainland feeders, but found only here, on Santa Cruz Island, the largest of the eight Channel Islands off Southern California. The azure bird has white brows, a gray vest, and a broken V striped across its white breast like a shirt collar. It scolds the three women who have summoned it on this January afternoon—PASHPASHPASH!—like a dapper old man grumpily demanding dinner.

Carina Motta is counting on this boldness. She presses her lips together in an approximation of the jay’s scold, calling it to a wooden platform loaded with acorns from the island scrub oak. The jay obliges by winging the seeds away and tapping each into the earth with its beak.

Feeding animals in the wild is generally frowned upon. But this particular interaction may offer a gentle shortcut for restoring oaks to damaged landscapes where they once stood, including the field where Motta now crouches with Minerva Rivera and Evelyn Bobadilla.

The three women are undergraduates working with Scott Sillett, a scientist at the Smithsonian Migratory Bird Center, and Mario Pesendorfer, a researcher at the center and the Cornell Lab of Ornithology. They’re using feeding platforms to lure jays from intact scrub oak onto recently burned land, hoping the birds will deploy their special talent there.

Island Scrub-Jays, like many other corvids, are “scatter hoarders.” Oaks produce acorns each fall, and the birds cache up to 4,500 each—far more than they eat. Those acorns that survive winter undevoured have a shot at becoming trees. When naturalist Joseph Grinnell observed California Scrub-Jays carrying acorns far uphill from oaks in the Sierra Nevada in 1935, he saw the “locomotion of the whole forest” borne aloft on birds’ wings.

The goal on Santa Cruz is to direct that locomotion, creating “little islands of oaks,” Motta says, and speeding the woodland’s march across the burn scar. It’s not a farfetched idea. After the last Ice Age corvids are thought to have accelerated the spread of North American beech and oak northward on the tails of retreating glaciers. In Germany, foresters have taken advantage of jays’ planting by preserving massive oaks and providing additional acorns in baskets. In an urban forest in Sweden, researchers estimate that it would cost up to $3,800 per acre annually to hire humans to do what Eurasian Jays do for free.

Minerva Rivera, Evelyn Bobadilla, and Carina Motta made up the field team for the Channel Islands project last winter. All three are part of the UCSB-Smithsonian Scholars Program, which connects underrepresented students from local colleges with opportunities like this one. Photos: Morgan Heim

The Santa Cruz study, now in its second season, will take several years to show whether enlisting jays is a viable restoration tactic. If it and similar studies bear out, they could suggest new ways to tap landscapes’ native healing powers, as practiced by their wild inhabitants, and stretch scant conservation funds farther. “That’s a really exciting possibility,” Sillett says.

There’s no shortage of places that need help, and California is high among them. The state has lost more than 30 percent of its oak woodlands, mostly to development. And though oaks are adapted for fire, climate change is driving more intense and frequent wildfires that can kill mature trees and even transform oak habitats into shrublands or grasslands. After 2017’s North Bay fires, Californians joined acorn drives and planted oak seedlings to stabilize soil, beat back invasive plants, and restore bulldozed woodlands in areas they share with scrub jays. Just imagine what the birds could contribute, Sillett suggests, if we carefully guided their skills. “You walk along these incredibly rugged landscapes of California, and it becomes quickly apparent to anybody that if you had a little blue seed-dispersing robot, that’s way more efficient than us lumbering around.”

The Channel Islands certainly count among California’s most rugged, and most altered, landscapes. In the 1800s, ranchers introduced tens of thousands of livestock including sheep, cows, and pigs to ecosystems unaccustomed to grazing; soon, grassland and barrens replaced oak chaparral and woodlands. By the time The Nature Conservancy purchased most of Santa Cruz in 1978, 10 plant and animal species were near extinction, and feral pigs and sheep ran rampant.

After the sheep were removed in the 1980s and acorn-eating pigs by 2006, native habitat rebounded: Santa Cruz’s scrub oak increased by 50 percent, right along with what Sillett’s work suggested was a 20 to 30 percent increase in jays. Other researchers found that the trees’ expansion was consistent with the jays’ seed-dispersal range. “That got us thinking, ‘Could the jays have been their own accidental gardeners, and recovered their own habitat?’” Sillett says. And, if so, would it be possible to enhance that process?

Decades of similar work from tropical forests offer some insights. These complex systems host hundreds of tree species, and the majority rely on animals to move their seeds around. It generally isn’t logistically or financially feasible for people to replant them at large scales. “Restoring the processes and attracting the dispersers makes the most sense because then the ecosystem can be self-sustaining,” says Karen Holl, a University of California, Santa Cruz researcher who studies forest restoration in Costa Rica.

That elegant approach is more complicated than it sounds. Many scientists have tried to jumpstart natural recovery by erecting artificial perches and nest boxes in abandoned pastures to attract birds and bats, which then poop out seeds they’ve eaten in intact habitat. But invasive grasses often outcompete new seedlings, halting forest recovery before it begins. Instead, planting a tree, or islands of trees, can provide a seed source and attract animals while shading out grasses, letting seedlings take root.

Seed dispersers’ helpfulness also depends on their numbers, and how much of their original habitat remains to provide seeds. In Brazil’s fragmented Atlantic Forests, where both native dispersers and habitat are limited, Wesley Silva of the Instituto de Biologia, UNICAMP, studies how feeding stations might turn whatever animals are available—including invasive ones like marmosets—into restoration “collaborators.” His vehicle of choice? Bananas packed with native seeds. The animals “are very fond of bananas,” he says. It is “the universal fruit.”

Because trees grow slowly, these techniques take time to produce results. In the western United States, for instance, scientists are planning a multicentury restoration strategy for whitebark pines where Clark’s Nutcrackers will be “doing the heavy lifting,” says biologist Diana Tomback of University of Colorado-Denver. Blister rust from Asia is wiping out the trees, alongside pine beetles and fire suppression. Agencies have spent decades collecting seeds, cultivating them, and screening seedlings for resistance to the fungus. Once they plant those whitebarks, they will lean on the birds to spread their seeds—a literal resistance movement. “It’s going to take a few human generations to get this done,” Tomback says. “Let’s hope someone has a good attention span.”

Sillett and Pesendorfer didn’t need a multi-­generational commitment; they needed a study site. Then, in March of 2018, managers lost control of a fire they had set on Santa Cruz to dispose of invasive trees. The flames licked through 260 acres of invasive fennel, then singed into scrub oak: a perfect margin from which to coax the accidental gardeners.

Island Scrub-Jays are not always amenable to coaxing, and on the second morning of the crew’s January field visit, Motta is having an understated faceoff. She walks with an acorn held aloft between thumb and forefinger, pishing over her shoulder at some stationary birds.

“You kind of have to build a relationship with them,” she explains.

“If we don’t have trust,” Rivera adds, “we don’t have anything.”

Gentle and sharply intelligent, Motta describes herself as a little old lady trapped in a 22-year-old’s body. She perfected her avian sound at a “pishing workshop” she attended solo in high school. At University of California, Santa Barbara, she was heartened to meet peers who racked up bird sightings the way others might accrue vinyl records. Still, she was not a collector so much as an admirer of beautifully interrelated things, and she soon resolved to study the ways animals and plants build worlds together.

The jays eye Motta skeptically, and she and the others change tack, throwing sterilized acorns into the grass as if chumming water to attract sharks. Finally, a pair descends on the feeding platform.

Rivera drops acorns onto a feeder. Photo: Morgan Heim

In past experiments, Pesendorfer and Sillett planted radio tags inside acorns to track how they fared. But the birds tossed all aside, “like, ‘To hell with this. This is bogus,’ ” Sillett says. It shouldn’t have been a surprise: Jays favor solid acorns over those riddled with insect tunnels, which, along with the birds’ habit of stashing seeds under protective brush, leads more to sprout. Now Motta, Rivera, and Bobadilla rush to follow the jays’ movements with more analog tools—binoculars, rangefinder, and GPS—setting waypoints for every acorn stashed. The women are part of the UCSB-Smithsonian Scholars Program, which connects underrepresented students from local colleges with opportunities like this one.

Six platforms stand inside the burn scar, each adjacent to the likely territory of a mated jay pair. Jays are mad for peanuts, so the crew used them to train the birds to see the platforms as food sources. Though they’re starting small, with 10 acorns per station per visit, the hope is to fill platforms with seed and walk away—a set of restoration bird feeders.

The crew’s island weekends unfold in a series of comedic dramas. There is backseat stashing, one jay re-hiding caches when its mate looks away. Others gulp three at once, gaping like gluttons. Sometimes, Motta says, the crew pishes for 15 minutes before realizing the jays are perched behind them, watching. In those waiting moments, it is quiet enough to hear the stroke of ravens’ wings—a sound Bobadilla loves. To her, the birds’ proximity is something from a Disney movie. “I’m telling you, I feel like Cinderella,” she exclaims after a hummingbird circles her head.

Top: The team selects and measures 10 acorns at random to plant in revegetation plots of burn scars. Later they will monitor those plots for seedling growth within burn zones hoping to get an idea of what kinds of seeds are most successful at germinating. Bottom: Test plots check the viability of the seeds Island Scrub-Jays have been tasked with planting. Photos: Morgan Heim

When the crew returns in May, there are green shoots—“our children,” Motta dubs them. They are unimpressive in stature, but made wondrous by the mechanism of their arrival. Eighteen baby oaks push up into the fire scar near the platforms. In sites where the crew didn’t feed birds, they find only one. Though the birds flew most of the seeds back toward the scrub oak, rather than farther out into the open, they hid more than 80 percent of the acorns within the burn scar.

By October a freshly graduated Motta has returned to the island to oversee a new crew as they fine-tune the study methods. This time, they’ll use chains of two platforms at each site to draw jays deeper into the scar and supplement acorns with toyon berries and islay cherries, both native shrubs that could shelter oak seedlings.

Ultimately, it will be critical to assess feasibility. “What’s the cost per germinating acorn that’s put out there by a human versus put out by a bird?” Sillett asks. And how likely is each to become a tree? Oak reproduction is fickle, adds Liv O’Keeffe, senior communications director at the California Native Plant Society, which is leading an effort to “Re-Oak California.” Acorns are viable for only a season, and seedlings die for countless reasons. “Anything we can do to improve the odds of an oak tree is important,” O’Keeffe says, so it may be best to encourage jays to help human planters rather than replace them.

Regardless, there’s already interest in the approach. With Sillett and Pesendorfer, the National Park Service hopes to tap Smithsonian Scholars for a study with California Scrub-Jays on the margins of the scar from last year’s Woolsey Fire, which charred 100,000 acres. About a fifth of that is on park land within the Santa Monica Mountains National Recreation Area, where unnaturally frequent and intense fires have raised concerns about a surge in invasive species. In a vicious feedback loop, that will lead to yet more frequent and intense fires, possibly converting whole ecosystems. The statewide story isn’t rosy, either: Total annual area burned has increased five-fold over the past five decades, likely driven by warmer temperatures drying out vegetation.

But even if using jays to speed the recovery of such places doesn’t prove cost-effective, Sillett says, its utility to students remains: It reveals the deep interconnectedness of living things and the myriad ways they sustain each other, made visible in a shower of seeds and a flash of blue feathers.

This story originally ran in the Winter 2019 issue as “Corvid Conservation Corps.” To receive our print magazine, become a member by making a donation today.​

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