The Bird Way

The penguins routinely dive for 5 to 12 minutes at a time. One penguin made a 27-minute dive on a single breath. Meir wanted to understand how these animals can stay underwater for so long. “They’re air breathers just like we are,” she says. “They take a breath before they dive and then use the oxygen in that breath for the entire time they’re down there.” One of their secrets: They slow their heart rate from 175 beats per minute to around 57 beats per minute, which allows them to slow the use of their oxygen stores.

More than two decades ago, Lefebvre invented the first scale of intelligence for birds, based on a bird’s behavior in the wild. How inventive is the species in its natural environment? Does it make use of new things and find creative solutions to the problems it faces? Does it try new foods? These activities are indicators of what’s called behavioral flexibility, which is one fairly reliable measure of intelligence. It’s the ability to do something new—to change your behavior to address new circumstances and new challenges.

Neurons in bird brains are much smaller, more numerous, and more densely packed than those in mammalian and primate brains. This tight arrangement of neurons makes for efficient high-speed sensory and nervous systems. In other words, say the researchers, bird brains have the potential to provide much higher cognitive clout per pound than do mammalian brains.

Crows are among the most frequent mobbers, swooping and dashing down on a hawk from above and behind it, always keeping the menace in sight. Gulls often resort to the practice, too, with an unusual twist: vomiting on the predator with keen aim. Colonies of fieldfares fire from another orifice, ejecting feces on a predator in such volume and with such accuracy that the threatening creature is literally grounded or stopped in its tracks. If enough of these droppings-bombs hit their target, they can soak a bird’s wings so it can’t fly.

The classic experiment demonstrating that birds can learn about threats from fellow birds was conducted by German zoologist Eberhard Curio. Curio showed that European blackbirds learned to regard a harmless bird as a predator by observing other birds mobbing it. He put one “teacher” blackbird in a box and showed it a species that was a real threat—a model of a little owl—which evoked a powerful mobbing response in the teacher bird. At the same moment, he showed another blackbird—the “observer,” or student—a model of a bird that’s harmless to blackbirds, a noisy friarbird. The student bird could see both the teacher and the friarbird but not the little owl. Almost instantly, it learned to fear, and mob, the friarbird.

The specificity goes even further. In white-browed scrubwrens and fairy-wrens, the number of notes encode information about how far away a predator is. The chickadee-dee-dee mobbing alarm calls of blackcapped chickadees contain messages—coded in the number of dees at the end of the call—about the size of a predator and hence, the degree of threat it represents. More dees means a smaller, more dangerous predator. A great horned owl, too big and clumsy to pose much of a risk to the tiny chickadee, elicits only a few dees, while a small, agile bird of prey such as a merlin or a northern pygmy owl may draw a long string of up to twelve dees. When I first learned this about the chickadee, it changed the way I heard all birds. What I’d taken as random chirps were in fact sophisticated signals to other birds, tweets of intelligence.

Magrath is still astonished by the results. “If I step out of my door here on campus and do a playback to the fairy-wrens, they understand what’s going on and flee. And if I walk five minutes up the road to the botanic gardens and do the playback, the fairy-wrens don’t respond. To me, this is very startling. It means the fairy-wrens do not respond to unfamiliar alarm calls until they learn that they mean danger—in effect, until they learn the new language.”

According to Suzuki, Japanese tits can even use grammatical rules to decode novel combinations of calls. Suzuki created a call that these birds had never heard before—an artificial sequence that combined their own ABC alert call with the tää recruitment call of another species, a willow tit. When he played the combination calls, the Japanese tits decoded the meaning of the ABC-tää combination, but not when it was played in reverse. This suggests that the birds are not just memorizing complex signals but rather applying a generalized grammatical ordering rule to decode messages.

In 2008, researchers at Duke University studying swamp sparrows discovered that the birds use “mirroring neurons” when they’re learning vocalizations, just as primates do. When one bird listens to another bird’s song, its neurons fire in nearly identical patterns of activity as when the bird sings the same vocalization itself. Imitation, then, is a way of connecting one mind to another.

The now classic example is the fork-tailed drongo of southern Africa, a shiny little black bird with a split tail, red eyes, and a hooked beak. Tom Flower, a behavioral ecologist at the University of Cape Town, followed 64 drongos for a total of 847 hours and found that these “kleptoparasites” use mimicry as a deceptive practice to steal food from a variety of species. The drongo’s repertoire of alarm calls includes 6 of its own and up to 45 mimicked calls from a range of birds and mammals, including the mongoose and the jackal. The drongo acts as an honest sentry for foraging neighbors, meerkats and southern pied babblers, perching high in the trees and warning of approaching danger with genuine alarm calls. But it also mimics specific alarm calls for larcenous purposes, falsely signaling an impending attack to startle a babbler or a meerkat into dropping its cricket or beetle and fleeing to cover so that the drongo can swoop in and snatch up the juicy morsel. Here’s what’s really notable: If the babblers and meerkats get wise to the drongos’ gambit and don’t flee as readily, the drongos counter with a rare deceptive technique: They shift to different alarm calls from their extensive repertoire so their targets don’t twig to their trickery. The birds even take their racket a step further, keeping track of whether they have duped an individual babbler and switching up the calls they use when attempting to steal again from that individual.

Birds also pirate other animal calls and sounds to fool predators and escape being eaten. Several birds that nest in cavities, both nestlings and incubating adults, hiss like a snake when disturbed by predators.

Pied currawongs are forty times the size of a thornbill, so the tiny bird has no chance of physically fighting off Darth Vader. But it does have a secret weapon: It cries wolf. Or, rather, hawk. Igic found that when a currawong attacks a nest, the thornbills send up multiple cries of alarm, mimicking a loud chorus of alarm calls by local species, creating the impression of impending attack by a predator that’s scary even to the currawong—the brown goshawk. The little birds don’t mimic the call of the big goshawk itself (which would be less effective—hawks don’t call mid-hunt); instead, they imitate the flurry of aerial alarm calls normally spurred by its presence, including—and perhaps especially—the calls of those reliable sentinels, New Holland honeyeaters. In response, currawongs flee immediately or take a moment to scan the sky. Either way, the mimicked chorus distracts them long enough for the thornbill nestlings to scramble out of their little dome nests

He imitates not just a single bird but many different birds producing alarm calls all at once, just as the brown thornbill does. “He’ll run the elements together to create an illusion of multiple birds alarm-calling, some near, some farther away,” she explains. “What he’s doing is mimicking the sort of live mobbing group chorus you would actually get around a threatening snake.” Why in the world would a male lyrebird do this in the middle of mating, with no snake in sight? Dalziell and Welbergen have a theory. The longer a male copulates, the better his chances of successful fertilization. To keep the female in place on the mound, he uses his masterful mimicry to deceive her, frightening her with a false chorus of alarms that may induce a “freeze” response or a reluctance to leave the male’s display mound. Some male moths also do this during copulation, mimicking the ultrasonic echolocation calls made by moth-eating bats to immobilize the female moth and further their chances of fertilization. In both bird and moth, the male is catching the female in a “sensory trap,” mimicking an alarm call and exploiting her fear response. She can’t afford to evolve resistance to such male trickery because the consequences of ignoring a mobbing chorus could be fatal. In this way, the male lyrebird uses his gifts of mimicry for vocal deception, misleading his mate, manipulating her biological response—lying to her—so she’ll crouch in terror while he finishes his business.

Before consuming autumn gum moth caterpillars, a crested shrike-tit will remove the digestive tract, which contains a poisonous oil from the eucalypts the caterpillars feed on. Vultures will leave aside the scent glands of dead skunks.

Nixons. A mix of black and turkey vultures, both with that undertaker’s shading, they’re a lugubrious sight, made more so by knowledge of their gross habits: a penchant for peeing on their own legs to cool themselves on hot days, vomiting their entire stomach contents when they’re under attack, and most of all, shoving those homely, featherless heads deep into the gore of a carcass to feed on its soft tissues, its eyes, mouth, and anus.

Vultures are nature’s sanitary workers. Because they feed in groups and eat rapidly—each bird downing more than two pounds of meat a minute—they can rapidly consume whole carcasses. Their guts are acidic enough to destroy the agents of disease, such as cholera and anthrax, so there’s little risk of spreading contamination from an infected carcass. That’s not the case with more leisurely mammalian carrion eaters such as rats or dogs or coyotes.

What happens when vultures vanish, people learned the hard way in India and Pakistan more than a decade ago. There, a mass die-off of oldworld vultures caused by an arthritis drug in the flesh of dead cattle led to an eruption of rabies. Dogs took over feeding on the carcasses, and the canine population exploded, along with the spread of the deadly disease.

When vision is limited, American robins search for earthworms by sound. Watch them in a field or on a lawn: They run a few steps, then lunge and drive their bills deep into the soil, more often than not snagging an earthworm. Scientists have recorded capture rates as high as twenty earthworms per hour. Mask all sound with white noise, as the researchers did, and the robins are not nearly as successful.

Stager also identified the specific scent that drew vultures to carrion. The discovery arose from a serendipitous conversation with field engineers at an oil company, who had been aware for some time that turkey vultures have knowing noses, and used the birds to locate leaks in natural gas lines. The engineers had figured out that if they introduced ethyl mercaptan into the line, they could locate leaks by the concentrations of turkey vultures circling above the line or sitting on the ground next to it. The same sulfurous chemical added to natural gas so the human nose can detect a leak, it turns out, is also released by an animal shortly after it dies. Thanks to Stager’s experiments, we now know that turkey vultures are highly attracted to the scent and can use it to find a target as tiny as a dead vole buried in leaves on the forest floor beneath a thick canopy of trees.

Puffins have such a fine sense of smell that they can find their colony by scent alone from a distance of nearly five hundred miles.

By sniffing out scented compounds—one chemical in particular, dimethyl sulfide, or DMS, generated when krill devour phytoplankton. Over the past two decades, Nevitt has parsed the impressive ability of seabirds to detect tiny amounts of the chemical. To our noses, DMS is that sulfury, briny smell of the seashore or oysters on the half shell. To seabirds, it’s the scent of sustenance.

A sensitivity to DMS also explains why seabirds consume plastics and other trash. Plastic debris emits the chemical scent, making trash smell like food and creating a kind of olfactory booby trap for seabirds.

Herons all over the world have learned to bait their catches, carefully placing leaves and dead insects on the surface of the water to lure fish. Pied kingfishers, black-crowned night herons, and green herons living in parks have learned that the bread people throw to ducks and geese will also draw minnows. They’ve taken to plucking up bits of bread and placing them on the water, then waiting with Job-like patience for a minnow to nibble and seizing it with a rapid thrust of their long, sharp bills.

They presented the crows with a puzzle box the birds had never seen before, which held a small food container behind a door with a narrow open slot along the bottom. They gave the crows long sticks, which the birds promptly inserted through the slot and used to push the food out through a window in the side of the box. Then the scientists gave the crows stick pieces too short to reach the food—some hollow and some solid, with different diameters so that they could fit inside one another. With no training or guidance, four of the crows put together the pieces within five minutes and used the longer compound pole to reach and extract the food. One bird was able to combine three or four elements to make one long tool—the first evidence of compound-tool construction with more than two elements in any nonhuman animal. This is truly a staggering accomplishment. Children can’t make these sorts of multipart tools until at least age five.

Raptors hunt at fires around the world—in the grasslands and savannas of Australia, Ghana, Brazil, Panama, Honduras, and Papua New Guinea—feasting on the easy pickings of prey fleeing the conflagration. There’s even a word for it: pyric-carnivory. Fire acts as a beater, driving organisms out of the brush.

It’s one thing to exploit an already raging fire; it’s quite another to start one yourself. But at least three species of raptors in northern Australia seem to be doing exactly that. Like raptors elsewhere in the world, fire hawks, as they’re called collectively—black kites, brown falcons, and whistling kites—hunt in the vicinity of bushfires. But witnesses have observed these birds doing something radically different: flying into active fires, picking up smoldering sticks, and then dropping them in unburned brush or grass, spreading the flames to new areas, presumably to flush out prey.

The ants are Eciton burchellii, the mini-lions of Costa Rica’s neotropical forest, ferocious pincer-jawed predators that capture nearly every arthropod in their path. They’re pouring out of a huge temporary nest site known as a bivouac. The nest is made of the bodies of live ants themselves linked to one another by their own limbs, creating a huge, jiggling, thermoregulated sanctuary for the queen and her larvae.

None of these birds are silly enough to eat the ants themselves. Rather, they mooch off the ants’ labors, swooping down and picking off creatures the ants have rustled out of hiding. It’s a good example of kleptoparasitism, that form of freebooted feeding in which one animal takes food that was caught, collected, or prepared by another.

Osvath tried experimenting with rooks. “They’re smart, but they’re difficult to work with when they grow up,” he says. “They don’t interact with humans, even if they know you.” But it’s odd how they’re drawn to universities, he says. “You find them in Lund, in Oxford and Cambridge. And for some reason, you find them in Uppsala, the other very large, old university city in Sweden, in the very far north beyond their range, where you wouldn’t normally find rooks. “I have a theory that they’re very academic.” “But difficult to work with,” I say. “Yes,” he says, “true of many academics.”

“If you put a chair in the aviary, for example,” says Osvath, “the birds will sit and look at it for two weeks. And then, all of a sudden, they’ll go for it, and it will take them like five minutes to completely dismember it. You never know what will scare them. You can think, ‘Oh, when I bring in this new experimental device, they’ll just freak out. But they don’t. And then one day when you walk into the aviary, they completely lose it, and you can’t understand what the problem is, until you realize, ‘Oh, I’m wearing new gloves.’

Osvath turned his attention to ravens in part, he says, because great apes are so like humans that for him they were “a bit boring.” “Sometimes—as a scientist I should perhaps not say this—but sometimes, ravens seem to be cleverer, at least in some areas.”

Among the recent findings about the intelligence of these birds: A 2019 study by Osvath and his PhD student Katarzyna Bobrowicz showed that ravens take only half as long as humans to select an object out of an array of objects based upon a single glance at the choices. This study suggests that the raven’s cognitive processing of visual input is faster than ours; its visual system picks up more information per time unit than a mammal’s does. Such speedy perception might affect the general speed of cognitive processing in more complex challenges, as well.

The experimenters also taught the birds how to trade that tool for a token, a bottle cap, that would earn them an even better reward. On tests in which they had to barter for the superior treat, the birds outperformed apes and even young children.

Often, the ravens will hang upside down by their feet from a branch, with wings outstretched, then let go—first with one foot, then with the other. “As far as I can tell, the game is about not extending your wings until it’s absolutely necessary,” says Osvath.

Andrew Skeoch has seen a group of choughs lying beside one another in a row, on their backs, legs in the air, passing a stick back and forth with their feet. He has witnessed the behavior repeatedly in this particular group but never in other chough groups, so he believes it’s a socially learned game.

In an ingenious experiment, Thomas Bugnyar of the University of Vienna and his colleagues found that ravens will guard their caches against discovery in response to the sound of another raven in an adjacent room—but only when a peephole between the rooms is open and not when it’s closed. This suggests that ravens are more than mere “behavior-readers” and can take the perspective of another bird, holding in mind what another creature can or cannot see—which some scientists consider a critical component of the sophisticated cognitive ability known as theory of mind.

But just a few weeks ago, all six birds were playing in the snow, “which they absolutely love,” says Osvath. “They do all the classical things, sliding down a hill, going back up, sliding down again. Sometimes on their backs with a stick in their feet. You can throw snowballs at them, and they all line up and try to catch them, jumping as high as possible.

Give a raven a jar or an empty flowerpot, and it will put its head inside and listen to the sound of its own voice, says Osvath. “It’s the same sort of sensory play you see in kids—it’s fun to talk into something that alters your voice.”

Some birds repeatedly drop objects and listen for the sounds they make. Galahs in New South Wales were seen dropping pebbles on the metal roof of a country house. Male spotted bowerbirds have been known to pick up shells from a heap and drop them on the pile, two or three times, apparently just to hear the little tinkle.

Studies by Lauren Riters of the University of Wisconsin and others show that song practice and so-called undirected singing of any kind outside the breeding season and at any age is intrinsically rewarding for a bird, involving those same opioid pathways active in experiencing pleasure. If that’s the case, if singing outside the breeding context is a form of play for the 4,500-plus species of oscine songbirds, then the estimate of play in only 1 percent of bird species is off by a lot.

That play—and especially complex play—is spotty among animals suggests that it evolved independently multiple times and may be important in some way. But its purpose has been a mystery, the hardest nut to crack, says Osvath. “We still don’t know why they do it.”

Laboratory rats deprived of play don’t develop normal brains. Scientists discovered this by housing juvenile rats with adults, which inhibits their play impulses. The young rats, which had all of the other kinds of social interactions—touching, sniffling, etc.—but no play, did not develop a normal prefrontal cortex. This, then, is another possible vital purpose of play in all animals: the healthy development of the brain.

Osvath has what he calls a “very shaky hypothesis” related to this. “Not even a hypothesis, just a thought,” he says, but it’s an intriguing one. Maybe play, especially for adult ravens, has a regenerative function for the brain. We know that the birth of new neurons—neurogenesis—occurs in birds that cache their food in the winter, especially in the hippocampus, the part of the brain responsible for learning, memory, and regulation of mood. (Evidence suggests that humans also have the ability to grow new neurons in the hippocampus throughout life.) “Maybe it’s like sleep, another mystery,” he muses. “You need it to regenerate and consolidate memories.”

Of course, there’s a proximate explanation for why ravens play, says Osvath: Because it’s fun. “We scientists are not supposed to say that, but almost every one of us—between the papers, so to speak—would agree that the animals we see playing are having fun, and that fun can be its own powerful reward.” In a recent study on object play in crows, ravens, and jackdaws, Osvath and several colleagues from Oxford University and the Max Planck Institute for Ornithology found that ravens offered the choice of food or play objects most often chose the latter. “The object play was so important they could say no to food,” says Osvath.

In most animals, play seems to be a powerful trigger for the release of dopamine, which is active in the reward system in the brain, and also for endogenous opioids, which are essential for sensations of pleasure.

The reward system is central to everything an animal does, says Osvath. It’s why we eat and why we have sex. It’s why some of us watch birds and why some of us study them. “A lot of us do things for no particular purpose,” says Osvath, “science, culture, writing books—we do these things mainly because we like to do them. It’s very much associated with our exploratory or play behavior. It’s completely useless to study birds or go to the moon or investigate any field that does not have practical applications. It’s getting basic knowledge, and that’s very interesting to us and we learn a lot from it, but it’s actually just play.”

analogy. If the birds push the right answer on the screen, they get a reward. “They all line up outside the little hut because they love to use the touchscreen,” says Wein. For her master’s project, Wein studied picture object recognition in kea, investigating whether the kea could transfer learning from photographs on the touchscreen to real objects, and vice versa. She taught the kea that one picture was positive and would yield a reward, and one was negative, and wouldn’t. “They learned really quickly to transfer what they knew from pictures to real objects,” says Wein, “like they scored 100 percent in just the second session.”

Such boldness and curiosity can get a bird into trouble. “Sometimes they’re too smart for their own good,” says Schwing. “A few months ago, a man shot at seven kea on his property because they had ‘uninstalled’ the satellite dish from his roof.”

Scientists suspect that laughter may have evolved from the breathy panting and labored breathing during play fighting and tickling between our primate ancestors and was used as a signal that everything is fine, now is a good time to socialize, play, explore together. It dates back at least to the common ancestor of humans and apes, some ten million to sixteen million years ago, but it probably goes back a lot further than that. Neural circuits for laughter reside in parts of the brain that are very old indeed, dating back to our earliest mammalian ancestors.

As Panksepp writes, “Ancestral forms of play and laughter existed in other animals eons before we humans came along with our hahahas and verbal repartee.”

Laughter in humans is far more than just a reaction to something funny. It’s a basic communication tool, a building block of society, defusing social tension and building social bonds. It also enhances both mood and well-being. “When we laugh, we feel happy and optimistic,” says Taylor. “We act friendlier, don’t argue as much, feel less stressed, and even become healthier.”

Lovebird pairs snuggle, gently preen each other, and nibble beaks, the bird equivalent of kissing. After separation or stress, they feed each other to affirm their bond. When a male approaches his mate, he sidles back and forth energetically, bobbing his head up and down, twittering, and then regurgitates some food into her mouth.

The male starts his performance by making a tool. With his huge hooked bill, he shears off a sizable stick from a tree, snips off the foliage, and then trims it to pencil size. This in itself is a wonder. Toolmaking of any kind is rare in the natural world and almost always occurs in the context of foraging. “This is the only species other than humans we know of that makes a tool for display or for musical purposes,” says Heinsohn. Holding his neatly fashioned drumstick in his left foot, the cockatoo beats it against his perch or the hollow trunk of a tree. When things really get going, he might mix in a high-pitched hooting whistle or lift his crest feathers, bob, sway, pirouette, and flash those naked cheek patches, bright red with flooded blood.

The team discovered that the cockatoos produce a regular rhythmic beat, like the beat setters of Western rock bands.

Sexual selection may run counter to natural selection, driving the evolution of extravagant male courtship traits that actually hinder survival tasks such as finding food and avoiding predators. In this way, males may end up with elaborate traits and displays that are burdensome but so sexy they’re perpetuated in the population.

Now we know that the female is in fact most often the hunter, the arbiter of mates, and her choice drives the evolution of male sexual display. But we’re still striving to understand just how. What are females looking for? And how do they distinguish a first-rate show from a flop?

But there’s another perspective, says Stoddard, more controversial but deeply intriguing. The hummingbird’s flamboyant dive may have evolved for a more capricious reason: “Simply because it’s beautiful!” she exclaims. “And females love it, and that’s enough to create selection pressure for aesthetically pleasing things.” Maybe, as Emerson said, beauty is its own excuse for being.

In creating this pattern, the birds use the same technique humans use in laying mosaics: Start in the middle—the center of the court—and work outward in both directions. When scientists destroyed the illusion by placing the smallest objects in front and the largest in back, the bowerbird quickly rearranged the stones to restore it. For good reason. The better the illusion, the better the bird’s chances of mating.

They build the interior of their avenues with red sticks that create a reddish light within the bower, actually changing the way the female sees. Exposure to this reddish light for a minute or more results in chromatic adaptation in the female’s eyes, altering her perception of the colored object he displays. As a result, she experiences stronger color sensations, especially with certain hues, like the magenta of the male’s crest. He also uses the structure of his bower to hide objects from the female and then flashes them to grab her notice.

The classic method for determining whether a behavior is purely instinctive or has a learned component is the so-called deprivation experiment—depriving an animal of an experience while it is young and then seeing whether it nonetheless performs the behavior flawlessly the first chance it gets.

That year, a photographer on Lake Bemidji in Minnesota spotted a female common merganser with seventy-six ducklings, which could not all have been her own. Rather, she was likely an older female experienced at raising young, and other females left their ducklings to her care in a kind of day care system called a crèche.