The Genius of Birds

by Jennifer Ackerman

The avian brain had no cortex like ours,

Humans and birds have been evolving independently for a very long time, since our last common ancestor more than 300 million years ago.

INTELLIGENCE IS a slippery concept, even in our own species, tricky to define and tricky to measure. One psychologist describes it as “the capacity to learn or to profit by experience.” And another, as “the capacity to acquire capacity”—the same sort of circular definition offered up by Harvard psychologist Edwin Boring: “Intelligence is what is measured by intelligence tests.” As Robert Sternberg, a former dean at Tufts University, once quipped, “There seem to be almost as many definitions of intelligence as . . . experts asked to define it.”

We also share with birds similar ways of meeting nature’s challenges, which we’ve arrived at through very different evolutionary paths. It’s called convergent evolution, and it’s rampant in the natural world. The convergent shape of wings in birds, bats, and the reptiles known as pterosaurs results from the problems posed by flight. To meet the challenges of filter feeding, creatures as far apart on the tree of life as baleen whales and flamingos show striking parallels in behavior, body form (large tongues and hairy tissues known as lamellae), even body orientation during feeding. As evolutionary biologist John Endler points out, “Again and again, in totally unrelated groups, we find many instances of convergence in form, appearance, anatomy, behavior and other aspects. So why not in cognition, too?”

If we can understand why two animals so distantly related converged on the same pattern of brain activity during sleep, we might solve one of nature’s great mysteries—the purpose of sleep.

Like Lefebvre, most scientists who study birds prefer the term cognition to intelligence. Animal cognition is generally defined as any mechanism by which an animal acquires, processes, stores, and uses information. It usually refers to the mechanisms involved in learning, memory, perception, and decision making. There are so-called higher and lower forms of cognition. For instance, insight, reasoning, and planning are considered high-level cognitive abilities. Lower-level cognitive skills include attention and motivation.

In these kinds of lab tests, all sorts of variables may affect a bird’s failure or success. The boldness or fear of an individual bird may affect its problem-solving performance. Birds that are faster at solving tasks may not be smarter; they may just be less hesitant to engage in a new task. So a test designed to measure cognitive ability may really be measuring fearlessness. Is the grassquit just a shier bird? “Unfortunately it is extremely difficult to get a ‘pure’ measure of cognitive performance that is not affected by myriad other factors,” says Neeltje Boogert, a former student of Lefebvre, now a bird cognition researcher at the University of St Andrews. “Birds, just like humans, will differ in how motivated they are to solve a cognitive test, how stressed they are about the test situation, how distracted they are by their surroundings, and how much experience they have had with similar tests. A raging debate is ongoing in the field of behavioral ecology on how we should go about testing animal cognition; thus far no clear solutions have emerged.”

What are the smartest birds according to Lefebvre’s scale? Corvids, no surprise—with ravens and crows as the clear outliers—along with parrots. Then came grackles, raptors (especially falcons and hawks), woodpeckers, hornbills, gulls, kingfishers, roadrunners, and herons. (Owls were excluded from the search because they are nocturnal and their innovations are rarely observed directly, but rather inferred from fecal evidence.) Also high on the totem pole were birds in the sparrow and tit families. Among those at the low end were quails, ostriches, bustards, turkeys, and nightjars.

“It’s not just about size—at least not in all animals,” says Lefebvre. “When we’re measuring brain volume, are we measuring information- processing capacity?” asks Lefebvre. “Probably not.”

“The problem is to get inside an animal’s head,” says Lefebvre. “Until now, the focus has all been on brain volume, whole, or of particular parts. But that’s not really where it’s happening. What’s controlling innovation and cognitive ability is not size, but what’s going on at the level of the neuron.” This brings to mind the advice that neuroscientist Eric Kandel, who won the Nobel Prize for his work on the physiological basis of memory storage in neurons, took from his mentor, Harry Grundfest. When Kandel was a young man, Grundfest told him, “Look, if you want to understand the brain you’re going to have to take a reductionist approach, one cell at a time.” Says Kandel, “He was so right.”

Clearly there’s more to a brain than mere size. But the truth is, birds have long had a bum rap in the size arena. Contrary to the cliché, the brains of many birds are actually considerably larger than expected for their body size. This is the result of an extraordinary process that also gave rise to our own oversized brains—although through a completely separate evolutionary path. Bird brains range in size from 0.13 gram for a Cuban emerald hummingbird to 46.19 grams for an emperor penguin. Tiny indeed next to the 7,800-gram brain of a sperm whale, but compared with animals of roughly the same size, not so small at all. The brain of a bantam bird weighs about ten times as much as the brain of a similar-sized lizard. Consider a bird’s brain relative to its body weight, and it comes out more like a mammal.

The dinosaurs that gave rise to birds possessed so-called hyperinflated brains even before the evolution of flight. The visual centers of their brains had already expanded to control the enlarged eyes and superior vision they used to avoid collisions while jumping from tree to tree, as had the regions of the brain used to process sound and coordinate motion. The avian brain evolved to deal with the sophisticated level of neurological and muscular coordination required to explore new niches and escape predators. In other words, bird brains came before birds, just as feathers did.

Birds experience the same cycles of slow-wave sleep and rapid eye movement (REM) sleep that humans do—patterns of brain activity that scientists believe play a crucial role in the growth of big brains, theirs and ours. Birds rarely have REM sleep longer than ten seconds, packaged into hundreds of episodes per sleep period, while humans have several bouts of REM sleep per night, each lasting ten minutes to an hour. But for both mammals and birds, REM sleep may be especially important for the early development of the brain. Newborn mammals such as kittens have much more REM sleep than adult cats. Human babies may spend up to half their sleep in the REM stage, whereas for adults, it’s about 20 percent. Likewise, studies show that young owlets have more REM sleep than older owlets.

Like us, birds also have periods of deep, slow-wave sleep in direct proportion to how long they’ve been awake. Moreover, in both birds and humans, the brain regions used more extensively in waking hours sleep more deeply during subsequent sleep—another similarity born of convergent evolution. A team of international researchers headed by Niels Rattenborg at the Max Planck Institute for Ornithology recently discovered this convergence in a clever study that made use of birds’ ability to do something we can’t do: modulate their deep sleep by opening one eye, limiting the slow-wave sleep to only one half of the brain while keeping the other half alert, perhaps to navigate while they sleep on the wing, and certainly to watch for predators (an ability that came in handy for the sleeping herons in the predawn darkness of one April morning, when they were attacked by a great horned owl). The team rigged up a little movie theater for several pigeons, blocked one eye in each of them, and showed them David Attenborough’s The Life of Birds. After staying awake watching the film for eight hours with a single eye, the birds were allowed to sleep. Studies of their brain activity showed deeper slow-wave sleep in the visual processing region of the brain connected to the stimulated eye.

That both humans and birds show this kind of localized brain effect suggests that slow-wave sleep may play a role in maintaining optimal brain functioning, says Rattenborg. “Overall, the parallels between mammalian and avian sleep raise the intriguing possibility that their independent evolution may be related to the function served by ...

Birds that migrate have smaller brains than their sedentary relatives.

Birds have been evolving separately from mammals for more than 300 million years, so it’s hardly surprising that their brains look quite different. But they do in fact have their own elaborate cortexlike neural system for complex behavior. In ornithological parlance, it’s called the dorsal ventricular ridge, or DVR. It arises from the same region of the embryonic brain during development as a mammal’s cortex does—the so-called pallium (Latin for “cloak”)—and then matures into a dramatically different architectural form.

Finally, in 2004 and 2005 came a manifesto rescuing the anatomical reputation of the bird brain. An international group of twenty-nine experts in neuroanatomy, led by two neurobiologists, Erich Jarvis of Duke University and Anton Reiner of the University of Tennessee, issued a series of papers overhauling Edinger’s misguided views and antiquated alphabet soup of brain misnomers. (It was not an easy task. One participant described the challenge of seeking consensus among the bird brain experts as an exercise in herding cats.) The members of the Avian Brain Nomenclature Consortium not only renamed the parts of the bird brain in light of modern understanding; they also related its structures to parallel structures in the mammalian brain so that bird biologists could talk to mammal biologists about what, in fact, were very similar brain regions in their respective subjects.

Both birds and humans appear to use working memory in a similar way. In our brains, the process that generates it arises in the layered cerebral cortex. But birds have no layered cortex, so how is information in the crow brain stored from moment to moment? To find out, Andreas Nieder and a team of researchers at the Institute for Neurobiology at the University of Tübingen taught four carrion crows to play a version of pairs, the game of memory that involves holding an image in mind while searching for its match. They showed the crows a random image. The birds then had to remember this image for a second before selecting the match out of four options by tapping the recalled picture with their beaks. Correct answers were rewarded with a mealworm or birdseed pellet. As the crows performed the task, the scientists observed the electrical activity in their brains. The crows were pros, accomplishing the matching task easily and proficiently. What was happening inside their brains? In what’s called the nidopallium caudolaterale region, an area analogous to the prefrontal cortex in a primate, a cluster of up to two hundred cells that were activated when the birds saw the original image remained activated while they searched for a match. This is the same mechanism that allows humans to hold in mind relevant information while we carry out a task.

One consequence of such modest threat from competitors and predators is that the crows are free from the burden of vigilance—in other words, they have the time and ease of mind to tinker with sticks and barbed leaves, to poke and probe, to bite and tear, and then probe again, without looking up. Freedom from threats may also have allowed for the evolution of a more leisurely childhood, in which young crows under the watch of their parents could dabble safely in toolmaking, refining their skills over a long period of time without starving in the process.

THE CROW stares back at me, intense, quizzical, as if asking what is so surprising. I wonder if the brain inside that black skullcap is any different from the brain of other corvids. Research suggests that there may be small differences. One study shows that the New Caledonian crow’s brain is bigger, at least compared with the brains of carrion crows and European magpies and jays. (However, as we know, overall brain size can be a rudimentary measure.) There is some ballooning in areas of the forebrain thought to be involved in fine motor control and in associative learning. This may improve the crow’s dexterity and boost its ability to pay attention to what it’s doing—a big advantage in any mental challenge. Moreover, as Russell Gray points out, New Caledonian crow brains have slightly higher numbers of glial cells, which in humans are thought to be involved in the mechanism of learning and memory known as synaptic plasticity. In sum, the brains of these crows may possess “no miraculous extra new structure,” observes Gray, “just small, incremental tweaks.”

“When these birds are problem-solving, they may be using forms of cognition intermediate between simple learning and human thought,” explains Taylor. The signatures of cognition evident in the crows’ behavior might represent the in-between steps along the way to our own complex cognitive abilities such as imagining scenarios or reasoning about cause and effect. “That’s why we’re really interested in these crows as model species,” says Taylor. “Pinpointing the cognitive mechanisms they use can offer insights into the evolution of human thinking and of intelligence in general.”

Whether New Caledonian crows have leaps of insight remains to be determined, but these experiments suggest that these birds do have an extraordinary ability to notice the consequences of their own actions, says Taylor, and to pay attention to the way objects interact. These are mighty useful mental tools when it comes to making and using material tools.

Is attention necessary for causal inference?

THE AUCKLAND TEAM IS also attempting to figure out whether the crows understand basic physical principles. A “crow-appropriate paradigm” for this, as Taylor puts it, is an experimental version of the old Aesop’s fable “The Crow and the Pitcher.” In that fable, a thirsty crow comes across a half-filled jug of water. Unable to reach the water to drink, the crow drops pebble after pebble into the pitcher until the water level rises enough for him to drink. As it turns out, this is not just a folktale. New Caledonian crows will do exactly that—drop stones into a water-filled tube to raise the water level. And as Sarah Jelbert discovered while working with the Auckland team, if given a choice between heavy objects and light ones, solid and hollow ones, the crows will spontaneously pick objects that will sink over those that will float. They know how to pick their materials and will select the right option 90 percent of the time. This suggests that the crows understand water displacement, a fairly sophisticated physical concept, on par with the comprehension of a child five to seven years old. It also suggests that they’re able to grasp the basic physical properties of objects and make inferences about them.

Lately, Taylor and Gray and their colleagues have been trying to worm out whether the birds understand the relationship between cause and effect, especially the effect of forces they can’t see. This is called causal reasoning, and it’s one of our most powerful mental abilities. Causal reasoning is at the root of our understanding that objects in the world behave in predictable ways and that mechanisms or forces we can’t see may be responsible for events. “We’re constantly making inferences about things we can’t see,” says Gray. If we’re standing inside and a Frisbee flies through our window, we understand that someone must have thrown it. The human ability to reason about causal agents develops very early in life. An infant only seven to ten months old shows surprise if a beanbag is thrown from behind a screen and then the screen is lifted to reveal a toy block rather than an expected human causal agent such as a hand. As Gray points out, this ability underlies our grasp of thunder and head...

In another experiment, this one on “causal intervention,” the crows didn’t fare so well. Causal intervention is a step beyond causal understanding. It involves seeing something transpire in the world and then acting to create the same effect. Say, for example, you’ve never shaken a fruit tree to release the fruit. But one day, you see the wind blowing a branch, causing the fruit to fall. And from that observation, you infer that if you shake the branch, you can act like the wind and make the fruit fall.

We “rub and polish our brains by contact with those of others.” —MICHEL DE MONTAIGNE

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The idea that a demanding social life might drive the evolution of brainpower was developed by Nicholas Humphrey, a psychologist at the London School of Economics, in 1976.

Only a few animal species have been known to reassure others in distress, among them great apes and dogs. Asian elephants were lately added to the list with a study showing that they may console a distraught individual with their trunks, gently touching its face or putting their trunk in its mouth—akin to an elephant hug. Not long ago, Thomas Bugnyar and his colleague Orlaith Fraser set out to discover whether ravens provide this kind of comfort to distressed mates or friends who are victims of a conflict. Do ravens feel sympathy for victims after an aggressive conflict? Do they console them? Consolation is of special interest, say the researchers, “because it implies a cognitively demanding degree of empathy, known in humans as ‘sympathetic concern.’” Consoling a victim means first recognizing suffering and then responding in a way that alleviates it for the sufferer. This requires sensitivity to the emotional needs of others—a trait once thought unique to humans and their closest relatives, chimps and bonobos. The scientists studied a group of thirteen young ravens. Before young ravens pair up and get territorial, they hang out in large flocks and cultivate valuable allies and partnerships. In any social group, conflicts may arise, and an “unkindness” of young ravens is no exception. Raven fights, especially those within a family, are usually minor squabbles involving a few pecks here and there. But fights between strangers or members of other families over nests, mates,...

this “funeral” was different. It was created by Teresa Iglesias and her colleagues at the University of California, Davis, who were interested in how scrub jays might respond to the presence of a fellow jay already dead. The team set out a dead jay in a spot in a residential neighborhood where the jays normally forage and recorded what happened next. The first jay to encounter the dead bird responded by calling in other jays with a bloodcurdling alarm call. The jays nearby stopped foraging and flew to the site, joining in a loud, cacophonous gathering, which got bigger and noisier over time. Were they mourning a fallen member of the jay tribe? Jeering in outrage? Trading ideas about what killed him or how to get him out of this place? The birds congregated around the body for half an hour before they flew away; for a day or two thereafter, they avoided feeding in the area. Reactions to the study quickly cycled from wonder (birds mourning!) to a heated debate and criticism of the researchers’ inappropriate use of the “f-word,” as one commentator put it. Some critics smelled straight-out anthropomorphism. This was hardly a funeral in the human sense. No, but the researchers weren’t suggesting that. They were just demonstrating how birds respond to a dead member of their own species: apparently, by noisily telling other birds about the death and perhaps alerting the group to danger, a behavior the scientists called “cacophonous aggregation.” In this sense, perhaps the scrub j...

Johan Bolhuis, a neurobiologist at Utrecht University, remarks on how strange it must seem to an outsider for scientists to be comparing birdsong with human speech and language. “If we were looking for some kind of animal equivalent, wouldn’t we look to our closest relatives, the great apes?” he asks. “But the odd thing is, so many aspects of human speech acquisition are similar to the way that songbirds acquire their songs. In the great apes, there’s no equivalent at all.”

Imitating human sounds is a lot to ask of a bird. We form vowels and consonants with our lips and our tongue, among the most supple, flexible, and indefatigable parts of the human body. For birds, with no lips and with tongues that generally aren’t used for making sounds, it’s a tall order to take on the nuances of human speech. This may explain why only a handful of species have accomplished the skill. Parrots are unusual in that they use their tongues while calling and can manipulate them to articulate vowel sounds, talents that probably underlie their ability to mimic speech.

Shigeru Watanabe explores the thorny question of how another creature may experience aesthetics at his lab in Keio University in Japan. Some years ago, Watanabe tested the ability of birds to discriminate between human paintings of different styles—for example, cubist from impressionist. In the earliest such study, he trained eight pigeons to distinguish between the works of Picasso and Monet. The pigeons came from the Japanese Society for Racing Pigeons; the paintings, from photos of reproductions in an art book. The experimenters trained the pigeons to spot ten different Picassos and ten different Monets by rewarding them when they pecked at the pictures. Then they tested the birds with new paintings by the artists, never seen during training—and with paintings by different artists in the same style. Not only could the pigeons pick out a new Monet or Picasso, they could also tell other impressionists (Renoir, for instance) from other cubists (such as Braque). (This early work won the scientists an Ig Nobel Prize for “achievements that first make people laugh, then make them think.”) To probe whether birds might be capable of making distinctions based on human concepts of beauty, Watanabe trained pigeons to distinguish between “good” and “bad” paintings, as defined by human critics. He found that the birds could indeed pick out the beautiful from the ugly using cues of color, pattern, and texture. All well and good, but do birds prefer any particular style of painting? To...

To see if birds are truly navigating, scientists put them on boats and planes and drive them around in cars (like those hostage sparrows) to land them in a distant, unfamiliar place with no clue of distance or direction. Then they release the birds and watch how they reorient. It’s called a displacement study, and it’s a powerful tool to investigate true navigation. Scientists suspect that pigeons and other birds navigate using a two-step “map-and-compass” strategy. First, they determine where they are at the point of release and which way they need to travel to get home. (This is the map step: In human terms, it’s the spatial coordinate system that suggests “I’m south of home, so I need to travel north.”) Then they use landmarks or celestial or environmental directional cues as a compass to keep them on the straight and narrow. The whole system, including both map and compass, appears to consist of multiple elements involving different types of information—sun, stars, magnetic fields, landscape features, wind, and weather. The compass part is fairly well understood, due in large part to thousands of studies depriving birds (often pigeons) of one sense or another, displacing them, and then seeing whether they’re thrown off course. Pigeons, like humans, are eye-minded creatures. It would be surprising if they didn’t use that grove of gnarled oak trees, that oxbow curve in the river, that hedgerow or weird triangular skyscraper, to home in on their lofts. And, it turns out, ...

Lots of creatures, from bees to whales, perceive magnetic fields and use them to orient. However, we’re still not certain how animals sense the fields. Detecting them with sensitive electronic instruments is one thing. But “sensing magnetic fields as weak as that of the Earth is not easy using only biological materials,” says Henrik Mouritsen, a biologist who studies the mechanisms underlying animal navigation at the University of Oldenburg in Germany. Birds possess no obvious sense organ devoted to the task. But because the field can pervade tissue, the sensors may be hidden deep within their bodies. One model holds that birds “see” magnetic fields with special molecules in the retina activated by certain wavelengths of light. Magnetic signals seem to affect the chemical reactions of these molecules, either speeding them up or slowing them down, depending on the direction of the magnetic field. In response, the retinal nerves fire signals to the visual areas of a bird’s brain, making it aware of the field’s direction. It all occurs at the subatomic level, involving the spin of electrons, which suggests something extraordinary: Birds may be capable of sensing small quantum changes. The sensing seems to involve a part of the forebrain linked to the eyes, known as cluster N. If cluster N is damaged, birds can no longer sense which way is north.

Wherever the sensor may be, it appears to be extraordinarily sensitive. In 2014, Mouritsen and his team reported in Nature that even extremely weak electromagnetic “noise” generated by human electronic devices in urban environments may disrupt the magnetic compasses of migrating European robins. We’re not talking cell towers or high-voltage transmission lines here; more like the background buzz of everything run by electrical currents. This news caused some shock waves in the scientific world. If it’s true, this kind of “electro-smog,” as it’s known, may already be causing birds navigational problems serious enough to affect their survival.

To navigate, a bird also needs something akin to a map to determine its position at the start of its journey—and where that space is in relation to where it’s going so it can head in the right direction. Do birds have such a thing? A map inside the mind? The idea goes back to the 1940s, when Edward Tolman, a psychologist at the University of California, Berkeley, first proposed that mammals might possess a “cognitive map” of their spatial environment. Tolman observed that rats in special mazes were able to figure out new, more direct routes or shortcuts to destinations that held a food reward. “In the course of learning,” said Tolman, “something like a field map of the environment gets established in the rat’s brain,” indicating routes, paths, blind alleys, and environmental relationships, which the rats may later call on. (Those who pursued Tolman’s vein of cognitive map research were affectionately known as Tolmaniacs.) Tolman proposed that humans, too, build such cognitive maps, and bravely suggested that these maps help us navigate not only space but the social and emotional relationships in “that great God-given maze that is our human world.” A narrow-minded map can lead one to devalue others and in the end to “desperately dangerous hates of outsiders” ranging in expression “from discrimination against minorities to world conflagrations,” Tolman wrote. The solution? Create broader cognitive maps in the mind that encompass bigger geographical boundaries and a wider soc...

WESTERN SCRUB JAYS—those masters of social trickery—remember not only where they stashed their caches (and who was watching) but also what they stashed there and when. This is important because the scrub jay squirrels away not only nuts and seeds but fruit, insects, and worms, foods that perish at different rates. Cached insects can spoil in days if the temperatures are high enough, while nuts and seeds can last for months. A series of creative experiments by Nicola Clayton and her team at Cambridge University showed that the birds retrieve the more perishable food before it rots, leaving the nonperishables, such as nuts and seeds, until later. The jays use their experience of how quickly food degrades to guide their choice in recovering their caches. Remembering that perishable food items may need to be retrieved sooner requires recalling cache locations, cache contents, and the time of caching. This ability to remember the what, where, and when of specific past events is thought to be akin to human episodic memory, the remarkable capacity to remember specific personal experiences. Like us, the birds seem to be using events that happened in the past (what they buried when) to figure out what to do now or in the future (dig up or save until later).

(Twilight is a rich source of information for navigating animals of all types. It’s the only period in the day when birds and other animals can combine light-polarization patterns, stars, and magnetic cues.)

WHAT IS THIS MAP made of? It may work like our Cartesian coordinate system, with different environmental cues that vary predictably along gradients providing information about latitude and longitude. To use these gradients, says Richard Holland of Queen’s University, Belfast, a bird “would have to learn that they vary predictably in intensity with space (and possibly time) within their home range and extrapolate this beyond the learned area.” But what are the sensory cues contributing to the map’s coordinates? Does it even have coordinates? Despite a welter of studies over the past four decades, we’re still trying to uncrumple the much crumpled matter of mapping cues. The gradient map may be partly geomagnetic. Holland and a colleague lately made a curious discovery. The pair picked up several European robins that had stopped over at a resting stage on their migratory path and exposed them to a strong magnetic pulse, temporarily disrupting their magnetic sense. Then they let the birds go. The young robins (which had no previous navigation experience) seemed unbothered by the pulse and continued on their expected path, guided by their innate program. But the adults flew off in the wrong direction. The researchers speculated that the adult birds had built up magnetic maps in their heads during their migrations, which they used to help them navigate on subsequent journeys. The pulses may have “reset” those maps, confusing the birds.

It may also cue them to the arrival of storms. A startling example of the apparent ability of some birds to anticipate impending storms recently came to light by accident. It was April 2014, and researchers at the University of California, Berkeley, were testing whether a population of tiny golden-winged warblers breeding in the Cumberland Mountains of eastern Tennessee could carry geolocators on their backs. The birds had arrived only in the past day or two after a 3,000-mile journey north from their wintering grounds in Colombia. The team had just attached the gizmos to the tiny warblers when all the birds suddenly flew the coop, spontaneously evacuating their nesting grounds. The scientists later learned that a huge “supercell” spring storm was headed their way, one that would spawn eighty-four tornadoes and kill thirty-five people. The warblers left twenty-four hours before the devastating storm hit and flew in all directions, some as far south as Cuba. After the storm passed, they flew straight back to their nesting site—for some, a round-trip of almost 1,000 miles. The scientists conducting the study suggest that the birds may have been warned by the deep rumble of the superstorm when it was still 250 to 500 miles away, picking up on the strong low-frequency infrasounds generated by such tornadic storms. These can travel for hundreds to thousands of miles but are inaudible to humans. Infrasounds are produced by many natural sources, but primarily by oceans. Interacti...

COMPARE ALL THIS WITH the ruddy turnstone, a small wading bird near the bottom of the innovative-behavior totem pole. In his book The Wind Birds, Peter Matthiessen describes an early experiment on the shorebird’s behavior by eighteenth-century English naturalist Mark Catesby: “Catesby provided a ruddy turnstone with stones to turn, the better to observe the feeding trait that gives the bird its name. In a time when scientific experiments were less complex than they are today, the bird was furnished systematically with stones that had nothing beneath them, whereupon ‘not finding under them the usual food, it died.’”

“AS A HUMAN BEING,” Einstein once wrote, “one has been endowed with just enough intelligence to be able to see clearly how utterly inadequate that intelligence is when confronted with what exists.”

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