An anesthetized crow enters a PET scanner in a lab at the University of Washington. The bird's welfare is always paramount; here the straps keeps its wings from getting caught in the platform. Photo: Andy Reynolds


Meet the Bird Brainiacs: American Crow

Corvid expert John Marzluff scans crows’ brains to crack the mystery of what makes these smart birds so successful.

​Editor's Note: Members of the crow family, known as the corvids, are among the smartest birds in the world. Some are capable of using tools, playing tricks, teaching each other new things, even holding “funerals.” And yet there’s still much we don’t know about these fascinating, sometimes confounding creatures. What’s going on inside the mind of a corvid? Three leading scientists are finding answers.

John Marzluff | American Crows (below)

Tim Shields | Common Ravens

Nicky Clayton | Eurasian Jays  

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The crows in your neighborhood know your block better than you do. They know the garbage truck routes. They know which kids drop animal crackers and which ones throw rocks. They know the pet dogs, and they might even play with the friendly ones. If you feed them, they probably not only recognize you but your car as well, and they might just leave you trinkets in return. These birds live their lives intertwined with ours, carefully observing us even as most of us barely take note of them. That’s how they survive, and they’re good at it: In recent decades the American Crow has taken over our suburbs, and even moved into the hearts of our big cities. As we’ve reshaped the landscape, we’ve created an ideal environment for an animal that is canny and perceptive enough to exploit our riches.

Exactly how the crow mind recognizes the opportunities we unwittingly provide is mostly an open question, says University of Washington wildlife biologist John Marzluff, who has studied corvids and their behavior for more than 35 years. He’s collected countless stories over the decades about crows’ complex social lives, including how they play, deceive each other, hold “funerals” around their dead, and seemingly learn from one another—even banding together to mob humans who have somehow wronged one of their own. Marzluff has a knack for figuring out how to quantify these intriguing behaviors in rigorous scientific experiments. By testing how the birds remember, communicate, and learn, his team is gaining insights into why crows are so street-smart and how they manage to thrive in our world. “Being open to possibility is important, so that you don’t miss really interesting new things that nobody thought these birds could do,” Marzluff says.

PET scan of a crow's brain: Courtesy of Robert Miyaoka/Dept. of Radiology/University of Washington

For the past several years he has been spying on crows’ thoughts to figure out what makes them tick. On a December morning a few of us are gathered in the small-animal neuroimaging lab in the University of Washington Medical Center to see a wild crow’s brain at work. Marzluff and graduate student Loma Pendergraft are testing how the crow processes the sight of food and the feeding calls of other birds.

The subject hops restlessly from perch to perch in a cage as Pendergraft plays a recording of wild crows in the midst of eating. A chorus of hoarse caws, fast double-caws, croaks, and barks fills the room; it’s as if we’re suddenly in the middle of a cornfield in summer.

But what is it like for this fidgety crow? These are his roost mates’ voices on the recording. Does he recognize them? Is his mouth watering as he anticipates the hunks of bread they’re cawing about?

Five minutes ago the bird was injected with a short-lived radioactive compound. As he listens, this tracer accumulates in the most active areas of his brain. In another few minutes, he’ll be anesthetized and scanned using positron emission tomography (PET), which detects the radiation and maps out the parts of his brain that were most responsive to the recording. Marzluff’s team will combine this scan with those from 14  other American Crows. Just as in humans, different networks in crow brains regulate different thoughts and behaviors; although not much is yet known about how bird neuroanatomy connects to bird behavior, some regions of the brain seem roughly similar to mammalian areas that handle functions like memory, fear, vision, and reasoning. Whichever ones the compound concentrates in will suggest what all that cawing means to a crow: maybe a general alert, a food’s-over-here signal, or possibly a warning for other birds to back off.

On the scanner monitor, the crow’s head looks monstrous—a chisel-like beak, huge bulbous eyeballs, and just a few hazy blobs indicating where brain action has taken place. The team won’t know which exact areas were busiest until later, after data analysis accounts for the background metabolic activity. But the crow’s work is done. Marzluff pulls the anesthesia mask away from its beak. Soon the crow’s eyelids begin to flutter. Pendergraft holds the groggy bird quietly in his lap for a few moments, making sure he doesn’t hurt himself flopping around. The crow is sleek and beautiful, his jet-black plumage glossy even in this harsh light. His long black toes, each armed with an impressive curved black talon, hang limp below Pendergraft’s hands.

A crow is anesthetized before entering the scanner. It has just heard recording of its wild roost mates, and the scan will reveal how its brain responded to the recording. The results will help researchers understand what information was communicated between the wild crows. Photo: Andy Reynolds

The crow is waking up to a ring of people staring at him—quite likely the strangest experience of his life. But he does not struggle or squawk. He is still, and his black eyes are bright, watching us watching him. Watching.

Marzluff got hooked on corvids in graduate school, studying how mated pairs of Pinyon Jays in the mountains of northern Arizona recognize each other’s voices. These birds’ complex societies include dozens of large interrelated families, with dominance hierarchies and ruling lineages.

As he finished his Ph.D., Marzluff learned that famed behavioral ecologist Bernd Heinrich had begun working with wild ravens. I gotta get in on this, he thought, and he and his wife, Colleen, promptly moved to a one-room cabin in western Maine to begin working with Heinrich. (It was small enough that they could put another log on the fire without getting out of bed.) They spent the next three years huddled in blinds, watching ravens and other forest creatures feeding on the dead animals they left as bait. “It was really rich,” Marzluff says. “Really primal.”

A dead horse or moose in the winter is a meat bonanza, quickly claimed and defended by whichever raven pair inhabits that territory. If a wandering raven spots it, too, the Marzluffs learned, it’ll enlist backup. “The pair will kick your tail if you’re alone, so it pays to go back to the roost and recruit others,” Marzluff says. Once a bird brings a minimum of nine allies, the territorial pair backs down.

Marzluff next moved to Idaho, spending seven years at the Snake River Birds of Prey National Conservation Area, advising the U.S. military on how its tank training exercises affected big raptors. He also got involved in a project to build captive populations of the Hawaiian Crow, which is extinct in the wild, by perfecting egg-hatching and chick-rearing techniques in close relatives: the American Crow, the Black-billed Magpie, and the Common Raven, which acted as surrogates for the island species. There are now 114 Hawaiian Crows in captivity, and some are being reintroduced to their former habitat this year.

Meanwhile, he kept thinking about the fascinating behavior he’d seen in wild birds—the way the animals organized their social groups, the groans and croaks and whispers that seemed so much like language. When Marzluff hired on at the University of Washington as an assistant professor in 1997, he could begin to explore the behavior of corvids in greater depth, by connecting lab-based experiments with tests of wild birds in action. American Crows were an obvious choice: There are plenty of them around Seattle, they’re easy to work with—and they do interesting things.

All corvids have relatively big brains for their size. But while a seed storer like a Pinyon Jay or a nutcracker has a huge hippocampus—a region involved in memory—crows and ravens are more like primates. They have exceptionally large forebrains, the domain of  analytical thought, higher-level sensory processing, and flexible behavior. (Marzluff calls them flying monkeys.)

Experiments in the 1990s and early 2000s demonstrated that mammals ranging from monkeys to sheep could recognize individual human faces. People had often claimed that crows could recognize them, too, but Marzluff decided to actually test it.

One of the Neanderthal masks researchers wore during the study. Photo: Andy Reynolds

As they trapped and banded crows around the University of Washington’s Seattle campus, he and his collaborators wore a latex caveman mask. When they later returned to those locations, either maskless or wearing a Dick Cheney mask the crows had never seen before, the birds ignored them. But anybody showing up in a caveman mask would spark a crowpocalypse. It wasn’t just the trapped birds that responded; apparently others had witnessed the abduction and remembered it. Whole gangs of crows followed the evildoer, scolding and dive-bombing. The birds knew that caveman face, and they didn’t like it one bit.

It was an impressive demonstration, says Heinrich, Marzluff’s former post-doc adviser: “He put it on the map. The rest of us just took it for granted.”

Every so often Marzluff’s group retests the birds. It’s been 10 years, and not only have the crows not forgotten, the knowledge keeps spreading. When a crow sees other birds mobbing, it joins in, learning and remembering the identity of the villain. Each time, more birds mob and scold. Nearly all of the birds originally trapped by the caveman are likely dead by now, yet the legend of Seattle’s Great Crow Satan still grows.

Brain-imaging follow-up revealed that faces associated with threats activated brain circuitry that’s analogous to well-known fear learning loops in mammals. Since these are some of the first behavioral imaging studies in wild birds, we don’t really know what it all means, cautions crow expert Kevin McGowan, a behavioral ecologist at the Cornell Lab of Ornithology. “It’s new, and it’s cool, but it’s like everything else: We need to get a bunch more data before we can see what the picture is.”

Recently, Marzluff’s graduate student Kaeli Swift turned to another corvid oddity. When crows see a corpse of one of their own species, they often gather around the dead bird, cawing noisily and then silently departing. Is it grief? Fear? A corvid Irish wake?

To find out, Swift fed wild crows in the same spot for three days. (It turns out they have a particular fondness for Cheetos.) Next she staged one of three scary scenarios to instigate a gathering: a masked volunteer holding an evidently dead crow (actually a stuffed specimen); a masked volunteer standing near a lifelike taxidermy Red-tailed Hawk (a dangerous crow predator); or a masked volunteer near both the hawk and the crow. In all cases, crows formed mobs of a dozen or so angry, raucous birds.

The following three days, the birds were measurably slower to approach the place for handouts. Many of them also remembered the masks associated with the dead crow. When someone wearing one of those masks showed up weeks later with no taxidermy props, the crows scolded and sometimes mobbed. In the paper she published with Marzluff last fall, Swift proposed that “funerals” are a teachable moment, in which the birds collectively make an association between potential danger and a particular spot or predator.

A researcher secures the crow as it revives Photo: Andy Reynolds

These experiments help to show why crows are so successful. They need only one experience to form a long-lasting memory of who can be trusted and who can’t—essential knowledge when you’re dealing with humans who might either feed you or shoot you. Crows also share information, allowing individuals to adapt to rapid environmental changes much faster than if they learned on their own.

The studies also get to the questions that any observant person begins to ask when watching a crow: What in the world is that bird doing, and why? Despite establishing a global reputation for his research, Marzluff hasn’t lost touch with that moment of wonder. “He just has fun,” says Willamette University biologist David Craig, who collaborated with Marzluff on the caveman mask study. “It’s a blast to spend field time with him. He’s maintained a curiosity-driven research agenda at the highest level.”

It’s a damp, gloomy evening in December, and the University of Washington Bothell campus is boiling with crows. They litter the grassy hill. They choke the tennis courts. Crows alight on the buildings and crows perch in the nearby Douglas firs. Many just stand patiently in the drizzle, like commuters in black trench coats waiting for the bus. Once it’s completely dark, they’ll join roughly 10,000 other crows in the winter roost in the wetlands just beyond.

Marzluff and I walk down to the roost. Every one of the hundreds of trees is festooned with crows, their black silhouettes sharp against the pale branches. It’s eerie, like a portal to an elfin realm. “It’s a great natural spectacle,” says Marzluff. “I think it’s the coolest thing ever.”

The American Crow is what urban ecologists call an “exploiter”—a species that not only tolerates humans but flourishes alongside us. It is far from the only one, as Marzluff has shown. A pioneer in urban ecology—the study of life in areas where we live, work, and play—he launched a long-term project in 1998 to explore how land use and development affect birds.

His team monitored more than two dozen locales in the city, in the suburbs, and in forested areas, some of which were slated for development. Four times every breeding season, they’d count birds, monitor nests, and tag fledglings. By 2010 they had completed nearly 6,000 surveys, documenting more than 55,000 individual birds from 111 species.

Grad student Loma Pendergraft wears a mask while catching a crow at an aviary at the University of Washington before preparing it for release. The bird and its mates have been at the facility for about two months. Photo: Andy Reynolds

The upshot, as Marzluff describes in his latest book, Welcome to Subirdia (2014), is this: Although some species disappeared as forests were converted to suburbs, many did quite well. Seattle suburbs host 30 bird species to the forests’ 20, including Song Sparrows, American Goldfinches, Anna’s Hummingbirds, and Pileated Woodpeckers. Many birds lived longer and reproduced better in the suburbs than in the forests. It’s not that surprising, Marzluff says. Low-density suburbs include a diversity of habitats, from woodsy lots to shrubby gardens to open areas. Plus, we supply birds with seed and suet, set up nest boxes, and eliminate many natural predators.

Marzluff does not soft-pedal the damage that development does to wild places or the threats faced by “avoider” species like Pacific Wrens and Swainson’s Thrushes. In the study, some of these birds basically vanished from all but the forested reserves.

But the study suggests that we could treat backyards more seriously as bird refuges. We can replace lawns with native vegetation, and provide food. We can mark windows so birds don’t fly into them, and keep cats indoors. We can maintain dead trees for birds to nest in, or set out nesting boxes. It’s more than feel-goodism. Bigger suburban bird populations will have better chances to survive the monumental threat of climate change.

From Marzluff’s point of view, these two lines of research connect via conservation. The only wild animals that many of us see regularly are pigeons and crows, but conserving species requires sacrifices that people won’t make unless they believe that wild animals are worth protecting. That’s one big reason Marzluff has written four books about corvids, partnering with illustrators to create appealing, accessible works. Backyard birds—like the perplexing, amusing, exasperating crow—can open people’s minds. Changing people’s attitudes and spurring them to create bird-friendly yards or take other personal action is harder than just preserving one piece of land, Marzluff admits. “But it’s a better long-term strategy.”

We’re standing on the side of a four-lane highway on the outer fringe of Seattle, and it’s not exactly a breathtaking wilderness. There’s a big gravel lot, a recycling yard, and an RV self-storage facility in view. But there’s also a creek, grass here and there, and a few clusters of conifers—a mixed landscape, the kind that Marzluff’s research suggests can be bird heaven.

This morning Marzluff will release nine crows used for Pendergraft’s experiment here, where they were trapped two months ago. He lifts a dog crate out of his car and sets it down on the gravel. He opens the door and steps back. Nothing happens.

He leans over, peers through the airholes: “Hey, you’re free!”

Marzluff releases a batch of research crows outside Seattle at the same place they were captured. Photo: Andy Reynolds

A moment later, a crow bursts out, flying fast with deep strokes of its powerful wings. It banks, heading west toward a thicket of bare trees a few hundred yards away. The bird lands in an upper branch and shuffles its feathers and tail, as if to shake off the indignities of the dog carrier and the humans who have been poking and prodding it for weeks.

The rest of the birds, six of them in a second crate, follow one by one, exploding out of the crates and then coasting in to land near the first bird. As we watch, a few other crows join them. It’s hard not to imagine that our bad reputation is now spreading, that Marzluff’s crows are telling their wild friends: You’ll never believe what those crazy people over there did to me.

In any case, for us humans below, it seems obvious that something must be going on between these birds, some form of communication that we haven’t yet even begun to crack. They know us so well, but we have much to learn about them.

Within 10 minutes, all the crows are gone.

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