Crows 1305
Crows and their fascinating behavior — it’s believed they can recognize human faces and have ‘crow funerals’ — get their own chapter in Berkeley writer Nathanael Johnson’s book Unseen City. Photo: Elaine Miller Bond

Berkeley-based author Nathanael Johnson’s book Unseen City was published in April, but its subject matter — the close examination of, and appreciation for, the nature that directly surrounds us — has provided him with particular comfort in the past few weeks.

“I’ve been finding peace by focusing intently on the life in front of my nose these days — there’s some relief in knowing that the antics of ants will continue even if the antics of a certain chaos president leads to global nuclear war!” he said a few days ago.

Scroll down to read an excerpt from Unseen City and for a chance to win a copy of the book by sharing your local nature photos.

Johnson will be giving a free public talk about his book Wednesday Nov. 30, 7:30 p.m., at a Shaping San Francisco event at the Eric Quezada Center for Culture and Politics on Valencia Street.

Unseen City‘s subtitle provides a good descriptor of what the father of two and food writer at Grist set out to achieve with this, his second book: “The Majesty of Pigeons, the Discreet Charm of Snails & Other Wonders of the Urban Wilderness.”

The idea for Unseen City came to Johnson  when he realized he couldn’t teach his then toddler-age first daughter the names of many local trees, as he didn’t know them himself. He decided he would explore the natural world on his doorstep with his daughter and write a field guide about it, grounded in their observations, and drawing on the help of experts.


Unseen City includes many fascinating revelations about the creatures that live all around us, but that can also become invisible to us, including pigeons, squirrels, turkey vultures — as well as plants like dandelions and ginkgo trees. Crows, for example, have been shown to be able to recognize human faces and gather for what appear to be funerals when one of their own dies. And Johnson surfaces theories as to why pigeons, who have astonishing mapping skills, often seem to have a missing or mangled feet.

The book also includes the first mention of Berkeleyside in a book: in his chapter on crows, Johnson refers to a popular March 2014 article by Ilana DeBare headlined Counting crows: Why are there so many in Berkeley?

Berkeleyside has one copy of Unseen City to give away to readers who help Johnson continue to collect images of nature in our midst. Simply tag your photos #berkeleyside and #unseencity if you are posting on social media. Photos can also be emailed to Johnson will select his favorite photo and we will alert the winner on social media or by email. Photos already shared with the author can be viewed on Unseen City‘s Instagram  feed, and Johnson’s full collection so far can be seen on Tumblr.

Excerpt from Unseen City: How so squirrels remember where they hide their nuts?

One cloudy morning I arrived at a coffee shop across the street from the UC Berkeley campus to meet Mikel Delgado. Delgado is a grad student who studies squirrels, which means that, rather than traveling to the rain forest to trap butterflies or scuba diving to observe whales, her subject of research is directly outside her door. Squirrel habitat is almost 100 percent coincident with student habitat.

She was waiting for me at an outside table, wearing a brown Carhartt sweatshirt, a green knit scarf, and purple glasses with gray checked temples. Her hair was black, with a few strands of white, and pulled back. She smiled and suggested we walk to her office.

“I’ve only just begun my research,” I told her. “You can assume total ignorance.”

She scanned for squirrels as we strolled, and seemed disappointed when they did not immediately appear. “It’s still early,” she said. “They may not be up yet. They are adapted to the schedules of the students.”

That is, because the people around them are not early risers, neither are the squirrels. They are attuned to their food sources’ rhythms, whether they be the seasonal production of tree nuts or the time of day at which college students are most likely to flip pizza crusts toward a charming tree kitten.

A pair of crows called from a treetop as we approached, and Delgado explained that squirrels react to crow alarm calls. The crows seem to sense danger a little sooner than squirrels do.

When we got to her lab, Delgado opened a big plastic tub filled with neatly partitioned nuts. She stowed a few handfuls of these in a fanny pack: pecans, walnuts, and almonds, all in their shells.

As soon as we emerged we began seeing squirrels. “Watch this,” she said, tossing a nut to one that approached us. “You’ll see he turns it ’round and ’round in his mouth, and he’s just feeling for what’s the best way to carry it, and maybe also checking for imperfections in the shell. If it’s cracked he might eat it right now rather than burying it and having it go bad.”

“How do they crack something like a walnut?” I asked.

“They have incredibly strong jaws. Before I started studying squirrels I got bitten by one while feeding it, and it really hurt. They have poor close vision, so they can’t see which is the nut and which is the finger. They have relatively clean mouths, they don’t often carry rabies, but they can carry other diseases, so it’s not a good idea to touch them.”

As she was saying this, another squirrel approached and pawed at my pant leg. “Step back!” I cried.

Delgado tossed a walnut directly at the beast’s head. It dodged nimbly and picked up its reward.

“So he’ll turn it,” Delgado said, “and then if you watch care- fully, they do this headshake.”

I watched.
I had seen nothing.
“It’s very fast. There was a student here, Stephanie Preston”—

now a professor of psychology at the University of Michigan— “who first noticed it. All these squirrel scientists had been observing them for years and no one had ever described this.”

It took me a good half hour of close watching before I saw it.

A few months later, watching videos of squirrels, I found it had become invisible to me again, and it only reappeared after I watched a video in slow motion.

It’s almost a flinch, a jerk over one shoulder and back. Scientists still aren’t sure why they do this; maybe they get a sense for the quality of the nut by rattling it in its shell. If insects have partially eaten an acorn, a squirrel will eat it immediately (along with the insects) rather than burying it.

Delgado studies the way squirrels store food. Different species have different food-storage strategies. First, there are the larder hoarders, which put all their nuts in one place and defend it. Then there are the scatter hoarders, and city squirrels fall in this category. It’s a diversified investment strategy: If someone else pillages a storage place, they lose just one nut. The problem with scatter hoarding is that squirrels end up with thousands of nuts all over the place, and they have to remember precisely where each one is, or else it’s gone forever.

It’s impossible to compass the enormity of this problem unless you’ve tried to do what a squirrel does. Forget about remembering the locations of thousands of nuts—do you sup- pose you could remember a single location? And to make things easier, instead of remembering that location for three or four years, as squirrels do, do you think you could remember it for just, say, five seconds? When I tried to do it, it resulted in utter, humiliating failure.

The squirrel had taken Delgado’s nut about fifteen feet away. It scratched at the surface for a couple seconds, deposited the nut, and then bent over to tamp it down with its teeth, arching its back and pumping twice. Then it brushed some dirt and pine needles over the spot and was off. The whole operation was over in a quarter minute.

Delgado suggested we try to find the nut. At first, this seemed a little bit unsporting. After all, I’d never taken my eyes off the spot where the squirrel had been. But I gamely walked over. Then, as I crouched down, something curious happened. The ground in front of me dissolved into an undifferentiated pattern of sticks and leaves and tufts of grass. Had the squirrel been right here? Or was it perhaps a half foot to my right? That actually looked more likely, and that’s where there was a bit of pine needle duff overturned, with the wet underside facing the sun. I brushed this away, but there was no sign of disturbed soil. I dug up a bit of ground with a stick. Nothing. Compacted clay. The idea that a squirrel had just made a hole there seemed impossible. I turned back toward my original spot, but I couldn’t pinpoint it now, and I noticed glumly that Delgado was searching several feet away. I disconsolately turned over more leaf litter. It was utterly hopeless. I’d have to dig up yards of dirt to find this nut. It did make me feel a little better when Delgado came up empty as well. Often she does find the buried nut, but not always. “This is just something that squirrels have evolved to be very good at,” she said. “Hiding nuts is one of their specialties.”

For many years researchers suspected that squirrels actually did not remember where they buried their nuts, and instead simply sniffed the ground until they located any subterranean stash at random. But the leader of Delgado’s lab, Lucia Jacobs, showed that this was not the case. Squirrels do sometimes stumble across (and eat) the nuts of others, but the vast majority of the time they dig up the nuts that they themselves have stored.

Henry Thoreau wondered at this as he tromped through the snow around Concord, Massachusetts. “In almost every wood, you will see where the red or gray squirrels have pawed down through the snow in a hundred places, sometimes two feet deep, and almost always directly to a nut or pine-cone, as directly as if they had started from it and bored upward.”

The problem here is not just that you have to remember that there’s a nut buried under the juniper bush (as it was in this case), you have to remember precisely which square inch under the juniper bush it is. Then multiply that by five thousand. Delgado wonders if it’s based on some kind of geometric mnemonic, with each squirrel filling in dots that sketch a shape, perhaps a giant spiral.

Do you like staying informed about Berkeley news? Then please consider becoming a Berkeleyside Member. Berkeleyside is also inviting readers to become investors through a direct public offering. Learn more.

"*" indicates required fields

See an error that needs correcting? Have a tip, question or suggestion? Drop us a line.

Tracey Taylor is co-founder of Berkeleyside and co-founder and editorial director of Cityside, the nonprofit parent to Berkeleyside and The Oaklandside. Before launching Berkeleyside, Tracey wrote for...