Human density can go hand in hand with biological diversity. Our civilization is not always a force desolating the earth.
That doesn’t mean that those trying to preserve wilderness are misguided or that we should be building condos in Yosemite. We need remote areas to support all the species that don’t thrive alongside humans. The point is that the places where people live, if thoughtfully designed, might also be places for the rest of creation to thrive.
Marzluff would like to see cities located near at least a hundred acres of dense forest, ideally consisting of native vegetation and abutting a waterway. Berkeley, for instance, which researchers found has a wide variety of species, borders a two thousand–acre wooded park.
I believe bringing people together with other species is beneficial, even for people who aren’t nature lovers. Evidence shows that stress levels drop and health improves when people are in the company of plants and animals. If we care about biodiversity and want to experience it personally (in addition to knowing it exists somewhere else, thousands of miles away), it’s eminently possible to increase the species richness of our daily lives by nurturing a variety of habitats in and around cities.
Flying Monkeys
Here’s another potential explanation for the rise of crows in cities: More people make more crows. Marzluff estimates that the territory a nesting family of crows controls is about the size of two backyards. That’s about one crow per person. This equation breaks down as density increases and backyards disappear under skyscrapers. But when a city is dominated by freestanding homes, an increase in population usually means more lawns and more garbage, and therefore more crows.
The attributes that allow crows to thrive in our company also make them interesting. They are innovative and flexible. They pay close attention to us, read our body language, and anticipate our intentions. Neuroscientists studying crows have shown that they can quickly and accurately infer the cause of an unexpected event. They also, like humans, can make mistakes about what causes what; in other words, crows can develop superstitions.
Sometimes they seem to toy with humans. Angell and Marzluff tell the story of a crow pilfering a sandwich from golfers and then returning the empty sandwich bag to them two holes later. Another pair of ravens stole a pie from sea kayakers, then bombed them with the pie tin the following day.
Crows use humans. They drop nuts and shellfish on roads to be smashed by our high-speed steel-belted radial nutcrackers. At certain intersections in Japan, it’s common to see crows tossing nuts into the road, waiting for the signal, and then walking with the pedestrians to retrieve their reward.
The birds quickly adapt to our ways. In the 1950s, when cars started zipping down the highways, crows would fly away from the sides of the road whenever a vehicle passed. By the 1960s, they were barely flinching as cars zoomed by.
New Caledonian crows, which have the largest brains among crows, use and even make tools. For example, they carefully trim twigs into hooks to excise insects from tight cracks. Some behavioral ecologists were skeptical of the amazing feats reported to have been accomplished by New Caledonian crows until researchers filmed one, Betty, using tools to lift a basket of food out of a cylinder. It’s an astonishing video. Betty first attempts to spear the food with a wire the researchers had provided. She considers a moment, then wedges a rod under a rock, deftly bends it into a hook, and fishes out the food. Betty does this nimbly, without a misstep. This video demonstrated that the crow is able to think three steps ahead: First, Gosh, it sure would be a lot easier to get the food if this rod had a curved end; second, Maybe I could bend the rod to make a hook; and third, I could use that rock to bend the rod. These birds are amazingly clever. To raise the bar, researchers devised an experiment in which the crow would have to pull up a string to retrieve a short stick, then use that stick to retrieve a longer stick, and then use the longer stick to get a piece of meat. The crow did it on the first try.
American crows are not as clever as New Caledonian crows, but they are still very smart. Researchers compare their level of intelligence to that of primates. “They’re like little flying monkeys,” Marzluff said.
Using Crows as Crows Use Us
In at least one way, though, American crows are considerably more resourceful than humans. Crows have exercised their considerable intelligence to exploit human quirks—our wastefulness with food, our reflexive desire to carpet outdoor spaces with grass, our predictable driving habits—but humans have devoted no thought to how we might take advantage of the rise of crows in our midst. Why are we the stupid ones in this relationship?
This question has obsessed Josh Klein for nearly a decade. Klein is one of those Information-Age Renaissance men who not only ponder crazy ideas, but also take the process a step further by engineering those ideas into existence. Klein’s ideas for making the relationship between humans and crows more reciprocal began in the form of a vending machine: He built a box designed to produce a peanut every time a crow inserted a coin. Then, working with a crow trainer, he demonstrated that the birds could learn how to find coins and exchange them for food.
When people hear about his crow box, Klein says, many tell him he’s going to get rich. He’s not optimistic about making money; he just wants to make the relationship between humans and crows a mutually beneficial one. He’s disturbed by the fact that very few people have noticed that some animals have changed to thrive with modern humanity. It’s not just crows, but raccoons, rats, deer, turkeys—by some estimates these species have larger populations than ever existed in North America before. “We have these animal populations evolving to take advantage of us,” Klein told me. “We can’t kill them off. And we aren’t doing anything to make it a more productive relationship. We are effectively breeding them for parasitism. I think it could be disastrous.”
The crow box is Klein’s contribution toward establishing a more balanced relationship. When I spoke to him, Klein said that he was redesigning the crow box because it had proved too difficult for some of the beta testers. I assumed that by “beta testers” he meant the crows and asked what it was about his machine that had been hard for them. He quickly corrected me: The crows were doing fine, the problematic beta testers were humans who had struggled to set up the machines. “Asking what about the crow box makes it hard for crows is like asking, ‘What about your front door makes it hard for your teenage son to use?’” he said. It’s clear that crows can work the vending machine; tame birds were ready to exchange money for peanuts after watching Klein set it up and test the box. But just because a teenage boy knows how to operate a front door doesn’t mean he’s going to be interested in coming home every night for a family dinner.
For crows, the mechanics were easy, motivation was much more complicated. After one crow learned how to work the vending machine, it began to hide the coins rather than inserting them for peanuts. Instead of being compelled to action by a reward of a peanut, it seemed to be compelled to watch the spectacle of its human colleagues searching furiously for the coins. Another time, Klein was training a crow using raw hamburger—to a crow, a more enticing reward than peanuts. While no one was watching, the crow hid some of the meat in Klein’s jacket pocket.
“When I was getting ready to go I put on my jacket, put my hand in my pocket, and screamed like a little girl,” he said. “The owner of the crow laughed his ass off, and the crow—they make this caw-aw-aw call that sounds like laughing.”
The very next time they met for a training session the crow snuck into the bathroom, stole some toilet paper, wet it in the toilet water, and cached it in Klein’s jacket pocket. When Klein put on his jacket and felt the wet mass, he jumped again, then gaped at the complexity of the practical joke.
There’s no doubt that crows can operate Klein’s vending machines if they want to, but it may turn out that they simply find it more entertaining to live off human excess than to work for peanuts. Whatever ends up happening with this project, in my opinion, it’s already a success.
No matter how efficiently it hacks the behavior of crows, it has already hacked the behavior of humans. Klein gets e-mails weekly from people who have heard about the crow box and want to know more. It’s snapped people out of their normal pattern of ignoring animals until they become a problem that can no longer be ignored. Klein is not going to single-handedly put us on a path to coevolutionary harmony with crows, but I do think he’s taken the right first step by replacing ignorance with curiosity and attention.
FAMILY LIFE
Though I’ve been looking, I haven’t managed to find a crow’s nest. They prefer conifers, Marzluff told me, because evergreens provide year-round cover. It’s apparently easy to mistake a squirrel’s nest for a crow’s nest. “Actually, squirrels’ nests typically start off as crows’ nests,” Marzluff said. But squirrels like to use leaves and pine needles, and crows prefer sticks. In addition, crows use grass whereas squirrels don’t, so McGowan looks for grass sticking out of the bottom of a nest.
In the spring, a mated pair will lay down a crosshatch of sticks (although in Tokyo, where coat hangers are more abundant than sticks, crows sometimes use those instead). Then they’ll add mud and grass. Finally, the female will line the nest with some soft and comfortable material.
Sometimes the offspring born the previous year will help with nest building. They stick around until they reach sexual maturity between the ages of two and four. Crows are different from most other birds in that the males sometimes stay even longer than that, until well after they are capable of starting their own families (the females, in contrast, always leave). They assist with feeding the next generations and cleaning up the nest.
The eggs range from sky blue to aquamarine, and are flecked with brown. Crows keep the nests clean by tossing out the chicks’ scat until they grow large enough to poop over the edge.
The chicks are ridiculous. They slump in the bottom of the nest as if they are dead, like sagging black assemblages of skin and delicate bone. But then, whenever there is a noise—a passing car, say, or a barking dog—they spring up like jack-in-the-boxes and open their mouths so wide that they all but disappear behind their straining red maws. As they age, the insides of their mouths darken and are fully black by the time they reach sexual maturity. If you think you might be looking at a juvenile, watch until it opens its mouth.
HINTS OF CULTURE
As soon as I started learning about crows, I began seeing them everywhere. It was almost as if all I needed to do was muse for a moment about some aspect of crow behavior to make one appear. But I had been unsuccessful in my attempts to eavesdrop on the more intimate aspects of their lives, and I certainly haven’t found much that would capture the curiosity of my three-year-old. No crow family has claimed my backyard as its territory, and the nests nearby must be well hidden, because I haven’t spotted any. Whenever I can, I stop to watch crows, but they quickly notice me watching them. Why is this human staring at us? I imagine them thinking, and then they wing away. Usually humans are blind to crows, and when we do pay close attention to them, they’ve learned that it often portends violence.
Nonetheless, I have managed to notice a few things I hadn’t seen before. For example, crows are almost always in pairs. They aren’t always side by side, though; they split and regroup, then split again. When they lose visual contact, they call back and forth until they are reunited. If the crows continue these calls, other crows also come. This gathering call is the classic caw-caw that you probably associate with crows. The scolding that accompanies the mobbing of a raptor has a harsher, screaming tone. Crows are said to have different warning calls for humans and raptors, but I haven’t been able to tune my ear to the difference. They make other sounds too: a clicking trill that sounds like a spoon rattling over a washboard, a bell-like chiming. Swift has recorded a two-toned moan, a rising minor second that sounds just like the famous half step in Jaws: duuh-duh, duuh-duh. No one knows what these sounds mean, and it seems likely to me, given the other similarities between crows and humans, that they mean different things in different places, depending on the local dialect. We know that each flock of crows has its own set of calls forming a sort of song. If an outsider is trying to join a flock and sings the wrong song, the group attacks. But sometimes outsiders stick around long enough to learn the group’s song, which, just as is often the case in human tribes, leads to acceptance.
Most of crow culture is inconspicuous, and they seem to like it that way, but a crow funeral is striking. It’s a sight strange enough to snap normally crow-blind adults out of their spells. When the birds come across a dead body of their own kind, they call in their neighbors. This can go on until a giant congregation is present. Scientists have observed crows placing objects near bodies, and even outlining them with sticks. Haupt has also witnessed what she called a “crow hospice”—a silent gathering around a bird that was dying.
Kaeli Swift is studying these funerals by laying a taxidermied crow on the ground. Each time the pair of crows that controls the territory sees this dead bird, they call their neighbors. Sometimes just a handful show up, Swift said, sometimes forty-five birds have come. They scream, then go quiet, then all scream again. It usually lasts for about twenty minutes. But Swift cautions that what she sees may be different from authentic funerals because she is introducing an unknown bird. “There might be a significant distinction between a stranger bird and a mate of ten years,” she said. For instance, Swift didn’t see any crows holding silent vigils, but there are credible documented observations of crows assembling noiselessly around the body of a compatriot.
Swift has proposed several possible explanations for the behavior. The first is that the crows come to study the cause of death and learn how to avoid it themselves. Avoiding death, along with successful reproduction, is an evolutionary driver powerful enough to create all sorts of behaviors. I have a pet theory that the human fascination with narrative grew from this evolutionary seed: The simplest, most gripping stories tend to be ones about narrowly avoiding death or finding love. So perhaps crows are storing away the lessons death and dying offer so they can pass them on to their chicks.
The second explanation is that these gatherings are less funerals than readings of the will. The death shakes the social hierarchy and the crows assemble to see what it means: Is a mate newly available? Is there territory to be claimed? Perhaps they watch each other and assess who is going to make the first move.
The other possible explanations are emotional rather than rational: The crows gather to grieve or to engage in some kind of spiritual ceremony.
There’s no reason that several of these possibilities can’t all be correct. In fact, it makes perfect sense that emotional and rational explanations would go together, given what we know of neuroscience. The experiences that are stamped most firmly into the memory are the ones accompanied by a powerful limbic system response. Emotion is the glue that makes reason stick.
To many people, roosts of thousands of crows and crow funerals are eerie. When a crow appears in a movie, it’s almost always an ominous symbol. But the influence of crows in our cultural heritage goes far beyond a gloomy omen. We recognize in these birds strange reflections of ourselves, and we gesture to these similarities to make meaning: You can find corvids embedded everywhere in our language. Marzluff and Angell point out that we have crowbars and crow’s-feet, we rave and are ravenous, we “eat crow” and reckon distance “as the crow flies.” These expressions suggest that crows and ravens might even have affected the way we think, because we’ve been using crow metaphors to explain the world for so long that they are now part of the bedrock of collective memory.
I value the cultural associations we’ve made with crows and all the meaning we have built atop them. But it troubles me that we now understand the crow much better as a symbol than as a bird. We’ve used crows to enlighten our own culture, yet ignore their culture.
It’s clear to me that crows do have culture. They pass on lessons to their children and compatriots. The
y play, and tease, and harbor grudges. They do things that seem illogical, implying deep and intricately reasoned motivations. Raptor mobbings and crow funerals suggest, at the very least, a keen, perhaps overactive, curiosity. At the very most they suggest culture: a collective, perhaps spiritual, affirmation of memory and community.
SNAIL
When a friend brought Elisabeth Tova Bailey a snail as a present, along with some field violets, she was perplexed and asked what purpose this creature was supposed to serve.
“I don’t know. I thought you might enjoy it,” was her friend’s reply.
Bailey was bedridden by a rare illness, or perhaps by the drugs the doctors had given her to cure it, and she was in no position to take responsibility for a pet, let alone exert the will necessary to enjoy the company of a snail. But then the snail unfurled itself from its shell, slipped down the pot, and consumed a single purple petal from a withered blossom. As she watched, Bailey became aware that she could hear chewing, like the sound of a tiny person eating a tinier stick of celery.
So begins Bailey’s beautiful, spare book, The Sound of a Wild Snail Eating. Bailey did enjoy her snail as her friend had hoped. Convalescence had reduced her to a snail’s pace, but she found some small consolation in this diminishment of speed. Bailey, often too weak even to roll over in bed, fixed her attention on the mollusk living a few inches from her head and began to notice things that most of us never see or hear. She would even contribute to the scientific literature on snails, making the first observation of a snail caring for its own eggs. The aim of the book you are holding is to persuade people (myself first and foremost) to slow down enough to see the wonders around us. Bailey, on the other hand, forced to move slowly, had no choice but to cling to the observation of small things. She wrote, “Survival often depends on a specific focus: a relationship, a belief, or a hope balanced on the edge of possibility. Or something more ephemeral: the way the sun passes through the hard, seemingly impenetrable glass of a window and warms the blanket, or how the wind, invisible but for its wake, is so loud one can hear it through the insulated walls of a house.” And so she trained her focus upon a snail.
Unseen City Page 17