Intrepid Navigators

“Birdbrain,” “silly goose,” “dumb as a dodo”—epithets like these reflect a widespread popular opinion that birds (except perhaps owls) aren’t very bright. Three recent books disagree energetically. “Crows and parrots perform as well as dogs in tests of reasoning and learning,” David Sibley writes in What It’s Like to Be a Bird. Jennifer Ackerman reports in The Bird Way that New Caledonian crows can assemble compound tools out of more than one element; children cannot do this until at least the age of five, she writes. Sibley describes an experiment in which ravens retrieved a piece of food floating halfway down a glass tube by dropping small stones into the tube until the water raised it to the top. He thought these birds had the problem-solving ability of a five-to-seven-year-old child. Sibley, previously known for guides to bird identification, came to believe while writing What It’s Like to Be a Bird that “a bird’s experience is far richer, more complex, and more ‘thoughtful’ than I’d imagined…. Birds are making decisions all the time.”

Although Ackerman is a science writer, not a professional scientist, she has extensively surveyed the scholarly literature about bird cognition in The Genius of Birds (2016) and now in The Bird Way. She is particularly interested in the structure and functioning of the avian brain, and in experiments that reveal how birds use experience, reasoning, and memory in decision-making.

A generation ago the pioneers of research into bird behavior assumed that it was largely innate. The Dutch-born Oxford biologist and ornithologist Nikolaas Tinbergen shared a Nobel Prize in 1973 for his work on animal behavior and communication, in the course of which he discovered that infant herring gulls get their parents to feed them by pecking at a red spot on the adult’s yellow bill. His co-winner Konrad Lorenz studied the phenomenon of imprinting: an infant animal becomes attached to the first thing it sees, which is normally its mother, and thus associates with its own kind. The geese that Lorenz raised personally were imprinted on him and followed him around his Austrian estate.

Today, Ackerman reports, research into bird behavior has swung strongly toward exploring conscious thought processes. This enterprise may be suspected of anthropomorphism—the projection onto animals of our own thoughts and feelings. Ackerman is alert to this danger, and in The Genius of Birds prefers to speak of “cognition” rather than the more human-sounding “intelligence.” Avian brain structures and neural connections are organized differently from ours, and birds’ experiences must also differ, she writes, though they may be rich in their own way.

Birds’ sensory organs, too, work differently from those of humans. Inevitably, birds inhabit a world of sights, sounds, and smells unlike ours. Bird vision exceeds ours in several respects: its power at a distance, its speed in resolving detail, its lateral breadth (in most cases), and its perception of a broader spectrum of colors. Notably, birds can see ultraviolet light. Some birds that look plain to us probably shine and sparkle to other birds. Birds can also detect the earth’s magnetic field, a sense that humans lack entirely. In a rare flight of fancy, Sibley imagines what a migrating black-and-white warbler “might see in the sky: a blue band of polarized light, and a reddish band oriented with the magnetic field with a stronger dot showing the slope of the magnetic field.”

For a long time birds were reputed to have no sense of smell. Audubon, for instance, proved to his own satisfaction that turkey vultures located carrion exclusively by sight. But in fact these birds have unusually large olfactory organs. They locate carrion by smell but prefer fresh carrion and thus disdained Audubon’s highly decayed offering. Oil company engineers nowadays add a sulfurous chemical to natural gas; they can then find pipeline leaks because turkey vultures will circle over them.

Birds can hear a wider range of sounds than humans, and hearing plays an outsized part in their lives. Although it may be a stretch to claim analogies to human language, as Ackerman does, birds communicate very actively by calls and songs. The two are not the same. Calls are short signals used year-round that can transmit socially important information: not merely the approach of a dangerous predator, for example, but what kind of predator it is—snake, hawk, cat, human. Birdsong contains more elaborate messages, usually related to breeding. They have various other functions: claiming territory, warning away rival males, and even, as sentimental humans imagine, convincing a female of the singer’s advantages.

Birdsong involves both innate and learned elements. The urge to sing seems to be innate in songbirds, for those raised in captivity try to sing upon reaching sexual maturity. Having never heard a male of their species sing, however, they produce babble rather than the appropriate song. As nestlings they learn specific songs from adult males, including their father, who sings nearby. The males of other species also sing nearby, of course, but some innate template prevents nestlings from learning their songs.¹ A window of readiness in the development of the young avian brain seems to enable this particular form of learning, just as a window favorable to language-learning exists in the development of human children.

Donald Kroodsma of the University of Massachusetts, a leading authority on birdsong, found by careful listening and recording that songbirds don’t just repeat the same phrases. They choose, apparently deliberately, within a repertoire.² Not all birds sing; about four thousand species, somewhat fewer than half the total, are classified as songbirds. These have specialized neuron clusters in their brains for creating and recognizing song.³

Nest-building is another complex avian activity in which inherited and learned behaviors mingle. Nest-building, like birdsong, appears even in birds reared in captivity and in isolation and so is likely an innate capacity. Construction techniques must also be innate, for each bird’s nest closely resembles others made by the same species. Astonishingly intricate workmanship can be involved. In Connecticut a few springs ago my wife and I watched a red-winged blackbird weaving long grass stems into its nest and attaching them by making a loop and then passing one end through the loop and drawing it tight. The selection of a site, however, must involve a more conscious choice. For example, a bird whose nest fails in one location usually tries a different, though species-specific, place.

Tool-using in birds arouses particular interest. The clever New Caledonian crow makes picks out of plant parts with which to extract otherwise inaccessible food. In captivity these birds bend wire into hooks for the same purpose. The woodpecker finch of the Galápagos Islands uses cactus spines similarly. A green heron has been filmed luring fish with a piece of bread. When the bread starts to float away, the bird realigns it. A fish nibbles and is seized.

Memory is another competence in which some birds surpass humans. The champions here are jays and other members of the crow family that store food for later use. Clark’s nutcracker, a member of the crow family native to the mountains of the western United States, can hide over 30,000 seeds and recall their precise locations many months later. These birds not only can locate their food caches but also conceal them from rivals, and they know to retrieve first those likely to spoil.

Elephants and dolphins recognize themselves in a mirror, displaying a sense of self rare outside human beings. If an experimenter places a stain on their bodies that they detect in a mirror, they attempt to remove it. Captive magpies with stickers placed on their feathers removed them once they saw them in a mirror. So far, magpies are the only birds shown to have this capacity. Though some can find concealed food by using a mirror, no other species is known to take actions that depend on self-identification in a mirror. Even the particularly accomplished African grey parrot Alex—owned by the animal behavior researcher Irene Pepperberg, who taught Alex more than one hundred words that he could apply to objects, actions, and colors, and also taught him to count up to six objects—when confronted with his own image in a mirror did not clearly identify it as himself.

Ackerman devotes an entire section of The Bird Way to play. It is not an activity commonly attributed to birds, so powerful is a crude evolutionary utilitarianism according to which only behavior that favors survival will spread in an animal population. Therefore some biologists have interpreted play in young animals as training for essential adult activities like hunting for food. Some adult birds, however, particularly members of the crow and parrot families, engage widely in activities with no apparent link to survival. The kea, a large New Zealand parrot, is, Ackerman says, “the most extravagantly playful of all birds.” Voraciously novelty-seeking and apparently “motivated more by play than food,” keas spend time tossing and catching objects and tussling with one another. Only slightly less playful are ravens, which, Ackerman tells us, have been observed sliding down snowbanks and other slopes, flying back up, and sliding down again. I have observed ravens executing complete rollovers in flight, an activity without apparent utility.

Emotion in birds is a tricky subject, vulnerable to the most egregious sentimental projections. Birds certainly experience some emotions; their fear or anger is often obvious. Seeking evidence of less overt emotions in birds, however, quickly turns speculative. Ackerman asserts that birds experience love and grief, but on this point, exceptionally, she offers no supporting evidence.

My wife and I once witnessed bird behavior that irresistibly suggested bereavement. In You Yangs National Park, near Melbourne, Australia, we came upon some white-winged choughs, striking crow-sized black-and-white birds known for a complicated communal breeding regime. They were dancing frantically around the corpse of one of their group that had been killed by a car. Were they mourning, expressing alarm, warning others, or simply confused? Their agitation and its cause seemed evident. But if it is only by inference from our own emotions that we dimly apprehend those of another person, how can we claim to fathom the emotions of animals?

Birds can recognize individual humans. Dr. Kevin McGowan of Cornell University, whose study of common crows required invading their nests and placing numbered and colored leg bands on their young, was thereafter singled out by the crows for angry attacks. Dr. John Marzluff of the University of Washington, an authority on birds’ adaptation to urban environments, found that some crows even give gifts to people who regularly feed them.⁴

Migration makes particularly heavy demands on birds. About 40 percent of the world’s nearly 11,000 bird species travel seasonally between a breeding area and a wintering area, which is sometimes thousands of miles away. This journey can require prodigious physical stamina. Bar-tailed godwits—pigeon-sized long-legged shorebirds—travel nonstop each fall from Alaska to New Zealand, a distance of over seven thousand miles. Lacking waterproof plumage, they cannot rest on the water. Seven days or more of uninterrupted flight requires a radical marshaling of the body’s energy sources, during which the godwit loses half its weight.

Migration’s mental demands are as daunting as its physical ones. Every autumn migratory birds find an appropriate location thousands of miles away for the nonbreeding season. Then they return in spring to the neighborhood of their birth for nesting. When nesting is done, they relocate to the identical winter quarters. This has been proven by marking birds, as Audubon did in 1803 by placing a silver thread on the leg of a nesting eastern phoebe at his mill in Pennsylvania. The bird returned to the same site the following spring.

One female rufous hummingbird displayed impressive navigational prowess. In the fall of 1996, misdirected on her way south, she wound up at a bird feeder in Agawam, Massachusetts, instead of in Mexico. Her migratory urges spent, she settled in and would have perished during the winter if she had not been transferred to a greenhouse in Northampton. Released the following spring, this tiny bird departed, presumably to her birth region somewhere in the Pacific Northwest, only to return to Agawam the following fall. She spent six successive winters in the Northampton greenhouse. Ackerman does not discuss this well-known case, but she mentions other marked hummingbirds that return to particular feeders after long absences. She further reports that hummingbirds have a sophisticated internal map that permits them to keep track of which flowers in a vast field they have already drained of nectar and which ones remain untapped.

Navigation requires not only situating oneself on a mental map, but also knowing in what direction and for how long one must travel to reach a destination. Migratory birds’ semiannual journeys mingle innate and learned behaviors. Travel restlessness sets in among migratory species when it is time to depart, probably activated by changing day length. This urge appears also in caged birds that belong to migratory species, even those reared in captivity and in isolation. Ackerman is little concerned with such innate behaviors, however interesting. Learning, however, may also come into play in bird migration, particularly in some larger species. Younger ducks and geese follow older ones already familiar with mountain ranges, rivers, and coastlines. In other species, like shorebirds, adults and juveniles go south at different times and by different routes.

Still more competences may assist in bird migration. In addition to the earth’s magnetic field, which birds can detect, low-frequency sounds like those made by the sea may help some find their way. Even smell may assist in finding a precise location. Bird navigation involves multiple capabilities, and Ackerman wisely admits that many remain mysterious.

Why do some species of birds burden themselves with the extra effort and risk imposed by migration? The inherent dangers of these long journeys, already considerable, have been greatly increased in recent years by the popularity among the inhabitants of some Mediterranean coastal countries, especially Malta, Cyprus, and Egypt, of shooting and netting millions of migratory birds. Parts of the Caribbean are not much better. This behavior is more a sport and a rite of passage for young men who can afford Jeeps and Kalashnikovs than a means of alleviating hunger.⁵ In Flights of Passage Mike Unwin and David Tipling estimate the toll at 500 million birds a year. They also explore the origins of bird migration briefly in their introductory pages. They repeat the scientific consensus that traces migration as an evolutionary adaptation to the end of the last ice age, when new territory became available, with abundant food and little competition but a harsh winter. Their aim, however, is not a review of scientific knowledge of bird migration but a “celebration of the wonders” of it.

Bird migration involves multiple strategies, far beyond a simple north-south journey. Ducks assemble in late summer at traditional locations hundreds or even thousands of miles from their nesting areas, where they undergo a complete plumage molt, becoming flightless and vulnerable for a time, before going south; seabirds like albatrosses and petrels follow an immense figure-eight loop from the South Seas to the north and back again when they have finished nesting; some desert species in Africa and Australia engage in nomadism in search of food and water.

Unwin and Tipling illustrate many of these strategies with a selection of sixty-seven species of birds, drawn from all the continents except South America. That continent has its own seasonal bird migration pattern that mirrors the northern one. Fork-tailed flycatchers, for example, move from temperate southern Argentina northward to the tropics for the austral winter. Unwin and Tipling also omit altitudinal migration between highlands and lowlands in the world’s great mountain ranges.

Otherwise their handsome book surveys most migration strategies, each species accompanied by a brief text and a rudimentary map of the routes followed. Though simple, these maps show the great variety of migratory behavior. I found only one that is misleading: the map for the northern wheatear, whose Greenland population returns eastward to Europe and whose Alaskan population returns westward to Siberia before going south. One might further object that some maps of seabird movements give an impression of random wandering, although these birds have routes and schedules.

That migration is not fully innate is shown by the existence of nonmigratory populations within largely migratory species, and the converse. Most Americans now know Canada geese primarily from their unwanted year-round presence on golf courses and in public parks. These nonmigratory geese are actually a human artifact, distinct from their migratory cousins that still pass southward each autumn in their familiar V-shaped skeins. Some of them descend from hand-reared geese that hunters once used as decoys. Farmers looking for additional income bred them for that purpose. When live decoys were made illegal in 1935, these semi-tame geese, now useless, were released. Spreading rapidly and breeding abundantly, they took up permanent residence in urban North America’s green spaces.⁶ The US Fish and Wildlife Service further augmented the resident component of the goose population by releasing birds hand-reared for hunting.

An opposite example, in which migration was gained rather than lost, is the house finch, a mostly sedentary resident of the American Southwest and Mexico. In the 1940s a few of these birds, which had probably been captured near Los Angeles, were released near New York City by bird dealers who feared prosecution for illegal trade in native American bird species when an Audubon Society inspector showed up. These birds prospered and spread throughout eastern North America. Some of that population now migrates south to avoid Yankee winters. This is likely a genetic evolution, those finches that moved seasonally having survived better than those that stayed put.

Birds are highly adaptable, and both their behavior and their physical characteristics may change as opportunities arise. The blackcap, a European warbler, formerly migrated in the fall from Northern Europe to Africa. As a milder climate and the practice of bird-feeding made the southern UK more favorable to them, those blackcaps that occasionally wintered there survived better than the population that was exposed to the dangers of crossing the Mediterranean, the Sahara Desert, and the Sahel and those regions’ annual slaughter. Blackcaps now commonly winter in the UK.

Such adaptation is possible because birds differ individually within species. The British ornithologist Tim Birkhead tells of the ancient practice, mentioned by Pliny the Elder, of training captive goldfinches to pull up a tiny bucket on a chain in order to obtain food and water. The birds pull up a length of chain and then stand on it while they reach for another length. But not all goldfinches tested by modern scientists could perform this trick, according to Birkhead. About a quarter of captive goldfinches figured it out for themselves. Another quarter could do it if they watched others. The rest never learned the trick at all.⁷

Of the writing and making of bird books there is no end, because they are profitable. Houghton Mifflin discovered this in 1934 when it took a chance on Roger Tory Peterson, an unknown young furniture decorator with a flair for illustrating birds. Peterson’s A Field Guide to the Birds took a novel approach: instead of the usual feather-by-feather descriptions, dauntingly complex, he offered simplified drawings that highlighted the unique field marks of each species. The guide sold out instantly, “literally gone on the publication date,” according to Peterson’s biographer. With accurate identification no longer requiring a shotgun, the modern hobby of birdwatching was born. Houghton Mifflin subsequently adapted the Peterson approach to a broad range of natural history subjects. More recently other presses, notably Princeton, have moved advantageously into bird books.

David Sibley is to some degree today’s Peterson. Since 2000 his field guides in various permutations have become the standard aids to bird identification in the United States. Knopf, his publisher, recently added trees and bird behavior to what has become the Sibley series. Unlike Peterson’s utilitarian drawings, Sibley’s guides aim for aesthetic pleasure as well as the clarification of identification criteria. In What It’s Like to Be a Bird he has put to a broader purpose his skill at giving volume and animation to two-dimensional images.

Despite its title, What It’s Like to Be a Bird is not a systematic study of bird cognition or behavior. It is a cornucopia of remarkable and disparate facts about ninety-six species of birds found in North America, illustrated as they pursue their daily activities. Each species is accompanied by a dozen or so bullet points providing interesting bits of information, not necessarily related to one another or to any single theme. The selection of species has some East Coast bias; only about a third are found mainly or entirely along the Pacific. This book will bring pleasure to the estimated 60 million Americans who are now said to spend at least some of their time enjoying birds, and perhaps will recruit some new ones. If only those who kill migratory birds each spring and fall could discover this gentler pleasure.