Top Quotes: “The Bird Way: A New Look at How Birds Talk, Work, Play, Parent, and Think” — Jennifer Ackerman
Introduction
“Earth is home to well over ten thousand different species of birds, many with marvelous, often Seussian, names — the zigzag heron and white-bellied go-away bird, speckled mousebird and naked-faced spiderhunter, the Inaccessible Island rail, pale chanting goshawk, shining sunbeam, military macaw, and wandering tattler.”
“Bar-tailed godwits migrate from Alaska to New Zealand in a single 7,000-mile flight, traveling day and night for seven to nine days — the longest recorded nonstop migratory flight. In terms of flying distance, the Arctic tern takes all, circling the world in orbittance, with the seasons. The bird flies from its breeding grounds in Greenland and Iceland to its wintering grounds in Antarctica — a round trip of almost 44,000 miles, the longest migration ever recorded. Over the thirty years of its life, a tern may fly about 1.5 million miles, the equivalent of three trips to the moon and back.”
“Males are flashier than females, which are often a dull color so that they blend in with their surroundings while they’re incubating eggs. Adults are more colorful than youngsters. Birds are brighter in the breeding season.”
“This book explores five arenas of daily activity for birds — talk, work, play, love, and parenting — and tells the stories of extreme examples.”
“Australian species crop up throughout the book.
There’s a reason for that. As biologist Tim Low writes in his brilliant book Where Song Began, “Extreme behavior in birds is more likely in Australia than anywhere else.” Australian birds occupy more ecological niches than birds anywhere on earth. They tend to be longer lived and more intelligent than birds on other continents. Also, Australia is where some fundamental aspects of bird being were born. Like song.”
“Australian magpies, loud, intelligent, often combative birds, known to launch vicious attacks on other species including humans when provoked. During the nesting season, you see bikers riding around wearing helmets festooned with elaborate forests of pipe cleaners or party poppers to deter the swooping birds.”
“A recent, more high-tech instance of bird ingenuity popped up in 2018 when a scientist tracking western gulls with geolocators to see where they fed was puzzled to see a gull traveling at sixty miles per hour for a distance of seventy-five miles, crossing the Bay Bridge from San Francisco to Oakland and traveling along the interstates before returning by the same route to her nest. It turned out that the gull, a female breeding on the Farallon Islands west of San Francisco Bay, had hitched a ride on a garbage truck bound for an organic composting facility in the Central Valley near Modesto. At first the researcher thought the bird might have gotten trapped in the truck. But then, two days later, the same thing happened. Clearly, this gull was using its head (if not its palate — as one Bay Area news reporter quipped, “It might be the only time a San Francisco resident ever drove to Modesto for dinner”).”
“Only lately has science luminated how birds can be smart with a brain at best the size of a walnut. In 2016, a team of international scientists reported their discovery of one secret: birds pack more brain cells into a smaller space. When the team counted the number of neurons in the brains of twenty-eight different bird species ranging in size from the pint-size zebra finch to the six-foot-tall emu, they found that birds have higher neuron counts in their small brains than do mammals or even primates of similar brain size. 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.
Moreover, says neuroscientist Suzana Herculano-Houzel, who led the research, in the brains of parrots and songbirds, most of the “extra” neurons occur in the pallium region of the forebrain, the part of the bird brain that corresponds to our cerebral cortex and is typically associated with intelligent behavior. In fact, big parrots like macaws and cockatoos, as well as corvids such as ravens and crows, have higher neuron counts in the forebrain than do monkeys with much larger brains — in some cases, twice as many neurons, with more connections between them — which explains why these birds are capable of cognitive feats comparable to those of great apes.
Birds have shown us a different way to shape an intelligent brain. Mammals use larger neurons to connect distant brain regions; birds keep their neurons small, close together, and locally connected and grow only a limited number of larger neurons to handle long-distance communication. In building powerful brains, says Herculano Houzel, nature has two strategies: It can tinker with the number of neurons and their size, and also, it can change their distribution in different parts of the brain. In birds, nature uses both tactics — to brilliant effect.”
Talk
“American robins, mockingbirds, warblers, sparrows, cardinals, finches all descend from the early passerines of Australia.”
“Scientists have found that at least five days before they hatch, the unborn fairy-wren chicks learn to imitate the call. Zebra finch parents can tell their young while they’re still developing in the egg that it’s hot outside. This is vital information for a growing chick. In hot climates, birds need to be able to lose heat, which is easier with a smaller body. When zebra finch parents are breeding in a hot climate, and the nest hits a temperature above 80 degrees Fahrenheit, they’ll chirp the news to their unborn chicks in the last third of the incubation period — the moment when the embryos are developing their temperature-regulation system. In response to these “hot calls,” the chicks will actually curtail their growth and emerge smaller — an adaptive advantage in the heat.”
“In conversation in nearly every human language, each turn lasts for around two seconds, and the typical gap between them is just two hundred milliseconds.”
“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.”
““This categorization of threats into those that are flying and those that are on the ground seems to be a pretty common strategy among birds,” says Mclachlan. The smooth-billed ani of the Caribbean islands gives chlurp calls in response to flying birds of prey and ahnee alarms in response to terrestrial threats like cats and rats. Japanese tits, relatives of chickadees, use two different alarm calls to specify the type of predator attacking their cavity nests. When a jungle crow approaches the nest to pluck nestlings from the entrance with its beak, the tits make a chicka call, which prompts the nestlings to crouch down inside the nest cavity. If a Japanese rat snake wriggles up to invade the nest, the tit’s jar call makes the chicks jump out of the nest to escape.”
““If you throw out a hawk model, the miners will go straight to the aerial alarm calls,” says Magrath. “When it lands on the ground, they switch instantly to the ‘churr’ mobbing calls. And similarly, if you plunk a predator on the ground, they’ll give the mobbing calls, and as soon as the thing leaves your hand when you start to throw it, they’ll switch to the aerial call. So there’s very clear encoding of predator behavior.”
“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 black-capped 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.”
“We think of whistles as a way of getting attention or carrying a tune, incapable of conveying much meaning, But go to Antia in Greece, the foothills of the Himalayas, the Canary Islands, the Bering Strait, Ethiopia’s Omo Valley, the Brazilian Amazon, and dozens of other remote places, and you may hear volleys of human whistled chirps, cryptic trills, and fluted duets, entire conversations of lilting whistles a lot like bird sounds that communicate with all the subtleties of human speech.
Julien Meyer of the University of Grenoble, France, has studied whistling languages for decades and has identified as many as seventy groups that use the language, most often in mountainous areas with steep terrain or in dense forests. Whistlers make their sounds in different ways, he says, sometimes by cupping their hands in front of their mouths, forming a resonant cavity, or rotating the tip of the tongue against the lower teeth, or putting two fingers in the mouth, or holding a leaf between the lips. In all cases, the result is a melody that imitates the syllables of ordinary speech. Whistled sound travels about ten times farther than spoken words, up to five miles in open places, and can penetrate the thick foliage of rainforest, so it’s useful to the shepherd in the mountains, the hunter in the forest, the farmer in the steep ravine. In the Canary Islands, the whistled form of spoken Spanish is known as Silbo, and the trills shepherds use to converse across ravines closely resemble the song of local blackbirds. In the small Turkish town of Kusköy, the local whistling language is called kusdili, or “bird language.””
“A series of five syllables in Turkish, Greek, or Spanish becomes five different whistles made with the teeth, tongue, and fingers. A fluent whistler can decode a “sentence” of tweets, warbles, and trills with 90 percent accuracy for simple sentences, about the same as speech. The languages are used to organize daily activities, announce an emergency, or transmit news or secret or private information, says Meyer. In parts of Southeast Asia, it’s used to convey love poems.
No one knows how these whistled languages began. In Greece, one theory holds that whistlers were posted as sentinels on mountaintops so they could warn of impending invasion or attack.
Sound familiar?”
“Researchers recently investigated the ubiquity of lying in day-to-day life in the United States and found that the mean number of lies told on an average day is one or two.”
“The bird world is rife with bluffs, masquerades, shams, and shell games. Some parent birds, such as piping plovers, feign a broken wing to draw predators away from the nest, fluttering erratically and making convulsive attempts to run, jump, or fly. Other birds distract predators by running in a crouched position like a small rodent. Still others, such as quail, feign death to fool their pursuers.”
“There’s a long history of people dying from trees falling in these forests. These are some of the continent’s tallest trees, and they lose their limbs the way North American trees lose their leaves. Around here, the eucalypts are called widow-makers.””
“Evidence for this social diffusion of mimicry comes from a story told often about a group of twenty lyrebirds caught between Toolangi and Warburton and introduced to the island of Tasmania between 1934 and 1949. The birds continued mimicking birdcalls from their old landscape for many years. Thirty years after they were released, their descendants were said to be imitating birds never present on the island, such as pilotbirds and whipbirds.”
“Dalziell and her colleagues caught on video twelve of these performances by males in their natural habitat — not an easy task given the lyrebird’s secretive nature and the green gloom of his forest home.
The videos reveal the details: The male bird on his mound sweeps his silvery tail up over his body, turning slowly around, shivering it theatrically and pouring forth a stream of song and mimicry. He flaps his wings and hops from side to side, all the while emitting songs, calls, castanet-like clicks, chirps, and chatters from his vast repertoire. He dances to only four types of songs, says Dalziell, and each song type is accompanied by its own moves. “He’ll coordinate his song and dance so that each different song has a unique choreography.” Just as humans waltz to waltz music and salsa to salsa music, she says, “so a lyrebird will dance a side step in time with a weird buzzing spew, spew, spew that sounds like a laser gun or a 1980s video game, and then, with his tail narrowed and wings flapping, jump or bob deeply while singing his more quiet plinkety-plinkety-plinkety song.”
Then, at the very end, he sometimes does something mysterious — abruptly breaks his song and dance routine and launches into a series of mimicked alarm calls.”
“Pied currawongs are forty times the size of a thornoil, 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 and hide in the thick vegetation around them.”
“When disturbed in their burrows, burrowing owls of the Americas rattle like an agitated rattlesnake to deter California ground squirrels or other competitors that might steal their burrows.”
“This is the case with male little hermits. in breeding season, the birds perform courtship displays at leks, communal areas in the dense undergrowth of the forest. There, some five to fifty birds sing and display to win mates. The song of the little hermit is a high-pitched, squeaky chittering of five to eight syllables that lasts only a second but is then repeated for as long as an hour between foraging breaks. At their leks, the birds sing long and hard from about seven a.m. to dusk, up to twelve thousand songs in a single day. Their songs are highly variable, with lots of little local dialects, even within a single lek.
“It’s crazy,” says Kapoor. “An average lek is about the size of an average house lot. You can walk from one end to the other in a couple of minutes. And within a single lek, you’ll get very distinct dialects. So it’s like everyone in the living room is speaking French, and everyone in the kitchen is speaking Swahili. It’s just totally bizarre that you would get dialects on that spatial scale.”
To sort out why the little hermits might have these “microgeographic” dialects, Kapoor studied the bird’s songs and their variations and how competition between males might shape them. During the breeding season, lekking males perch on a special slender twig and vigorously defend their territories by singing while wagging their little white-tipped tails. Most males occupy their singing perches and territories for less than a year, though a few lucky ones may persist as long as seven years. If you’re a young male, it’s hard to win your own territory. Young males seeking to join a lek use their gifts of imitation to impersonate existing territory holders. “First, they’ll sit out on the edges of the lek listening,” explains Kapoor. “Then they’ll sneak around and eavesdrop on different individuals, focusing in on one local bird — let’s call him ‘Fred’ — listening to him and learning his song. Then they’ll go off into the forest and practice by themselves. They sound horrible at first, squeaking away, and for the first couple of weeks, you can’t identify what they’re trying to copy.” But the young birds practice and practice, and over the course of a few weeks, they get much better.
“By the time a young male is ready to come back and take his place on the lek,” says Kapoor, “he sounds exactly like Fred — or at least, one of his close neighbors-so I know exactly where in the lek he’s intending to go.”
And here’s the creepy part: Kapoor suspects that a newcomer “mimic male” may attempt to usurp an established male’s territory by attacking and killing him and then taking his place — if he himself is not killed in the process. This is still just a hypothesis, yet to be observed, but Kapoor has seen brutal fights that lasted a week or more, with the birds trying to stab each other with specialized sharp tips on their bills. If a young mimic male is successful, “thereafter, he would likely be treated by the other birds in the lek as if he were actually Fred, their local neighbor, and tolerated as the rightful owner of his territory,” he says. “The other territory holders wouldn’t know the difference because his mimicry is sufficiently well practiced to fool them.””
Work
“Some birds take on extremely challenging prey. Consider the short-toed snake-eagle, a raptor of southern Africa with a name like a hybrid from Greek mythology. When the snake-eagle spots its reptilian prey from high in the sky, it dives down, seizing the snake with its talons and lifting off again with the thrashing, striking serpent in its clutches. While still in flight, it crushes or rips off the head, then swallows the beast whole. With equal delicacy, its cousin the brown snake-eagle consumes venomous snakes such as black mambas and cobras up to nine feet long.”
“I once watched a pied butcherbird eat a deadly cane toad in the suburbs of Brisbane. Think about what’s involved in this. The new-world toad was introduced to Australia in 1935 and spread quickly from Cape York Peninsula to Sydney and west beyond Darwin, bringing death to predators unfamiliar with its venom. Over just a few decades, pied butcherbirds, along with a few other clever species-Torresian crows, black kites, pied currawongs, white ibises discovered the trick of avoiding the toad’s poisonous parts, the glands on the back of its head and the skin itself. Otherwise the toad is well worth eating. Their technique: flipping over the toad and eating from the belly side inward. Ibises consume only the toad’s legs. Black kites eat only the tongue.
Kea parrots of New Zealand eat more than a hundred different plant species, some of which are highly poisonous, with roots, stems, leaves, and seeds all containing toxins. Only the fruit pulp is edible, and kea have learned to root it out.
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.”
“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.”
“As most of us now know, turkey vultures have gotten a bad rap. The truth is, those naked heads relieved of adorment are extremely hygienic — gory stuff just doesn’t stick. And it’s a lie that vultures particularly relish a ripe, rotting mess. They actually prefer fresher carrion. As such, they perform a vital, and vastly underrated, service to the environment: the quick, competent cleanup and recycling of dead creatures.
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 old-world 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.”
“Sharp as the human eye is, it doesn’t hold a candle to a wedge-tailed eagle’s, which can see three to four times farther than we can. An eagle’s retina is more densely layered with cones than ours is, making its visual acuity, the ability to perceive detail and contrast, far better than ours. In the center of its eye is a specialized deep fovea — a little convex pit coated with cones — that may give its eyes extra magnification in the center of its field of view, like a telephoto lens, the better to spot that field mouse from hundreds of feet.
Birds top us in color vision, too. They see hues beyond our imagining. Humans have three types of color-receptive cones in our retinas, blue, green, and red. Birds have a fourth color cone that is sensitive to ultraviolet wavelengths. We are thus “trichromatic,” and most diurnal birds are “tetrachromatic.” With their extra UV cone, birds can distinguish shades of color we can’t tell apart, allowing them to spot prey well camouflaged against the uniform background of a grassy field or leafy forest floor, and to detect things invisible to us — like the trail of urine left by a vole.
But it goes beyond this. Birds see a massive spectrum of color our brains are simply incapable of processing.”
“In 2019, biologist Dan-Eric Nilsson and his colleagues at Lund University in Sweden released photos from a camera designed to re-create how birds see color in their surroundings. With the help of special filters, the camera simulates the full visual spectrum of birds. One major discovery: To birds, the dense foliage of a rainforest likely looks not like the uniform, largely flat mass of green we see, but a detailed three-dimensional world of highly contrasting individual leaves. I have tried to see this way, to pick out distinct leaves amid the wall of green, but contrasts in green are hard for humans to distinguish — which is what makes the green catbird in the rainforest so impossible to spot. UV light amplifies the contrast between the tops of leaf surfaces and their undersides, so the three-dimensional structure — the position and orientation — of the leaves pop out. This makes it easier for birds to navigate through complex leafy environments and to find food there.”
“In 2018, I spent an hour in an aviary with “Percy,” a great gray (Lapland) owl, a species that listens for voles and other rodents tunneling through loose soil and can hear them at a distance of hundreds of feet, even if they’re beneath two feet of snow.”
“If you think about where owls are hunting, the natural conditions they face, the Blakiston’s reliance on vision and the great gray owl’s reliance on hearing make sense, says Jonathan Slaght. Great gray owls hunt where it’s flat, with snow and quiet. Fish owls regularly hunt in narrow river valleys, with shallow, fast-flowing, and rocky waterways. “If a fish owl had hypersensitive hearing and hunted in these waterways, it would go crazy,” he says. “It’s so loud that trying to isolate the sound of prey in that type of habitat would be impossible. The fish owl does have a facial disk, but it’s nowhere near as pronounced as that of a great gray owl or a barn owl, which can catch things in 100 percent darkness because of their heightened hearing ability.””
“The oilbird is the only nocturnal fruit-eating bird in the world. The huge flocks of several thousand birds spend their days roosting and screeching in the blackness of the cave. Every night they set out in silence to forage in the surrounding forests for fruits of palm and laurel trees, which they swallow whole, regurgitating the seeds.
Imagine living so deep within a cave that no daylight penetrates, and not once in your life experiencing any illumination brighter than the moon. The oilbird has developed tools to negotiate its dark world: It has special long bristles around its beak, which it uses for tactile sensing, the better to probe fruit and other necessities through touch. It also has the most-light-sensitive eyes of any vertebrate on earth, with a higher density of rods in its retina, some one million per square millimeter, which allow it to see at night while foraging in moonlight. But in the total darkness of the deep cave, where the bird roosts and nests, it needs a guidance system beyond touch or vision.”
“The kiwi of New Zealand, the only bird with a nostril at the tip of its beak rather than at the base, uses its nose to unearth worms, invertebrates, and seeds. 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.”
“These species routinely travel in the dark or under conditions where visibility is limited by fog or extreme cloud cover,” says Nevitt. “Their survival depends on finding the proverbial needle in a haystack on a daily basis.”
How do they do it?
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. “Birds tend to be attracted not to prey scents per se,” she says, “but rather to odors such as DMS that are released during feeding interactions” — a euphemistic term for the ravaging of prey by predators. In other words, says Nevitt, “predators tend to be messy eaters, and tube-nosed seabirds have adapted to pay attention to who is eating whom.”
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.
Some birds get at food enclosed in hard shells or other tough packaging by dropping it on pavement to crack it open. Gulls drop clams, and crows and ravens drop nuts.
Perhaps most notable is the lammergeier, or bearded vulture, a carrion-eating bird like the turkey vulture, but one that feasts on bones rather than flesh. Small bones it swallows whole; large femurs and ulnas it takes to the sky, letting them go from hundreds of feet over rocky outcrops to split them open and release the marrow. It has its favorite spots for bone breaking, known as ossuaries. This huge and lovely bird is thought to be the one that killed Aeschylus when it dropped a tortoise on the Greek play-wright, mistaking his bald head for a stone.”
“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.”
“If kites and falcons have learned to manipulate fire to flush out prey, this would be the first known use of fire as a tool by any nonhuman animal, overturning some old entrenched assumptions the orthodoxy that only humans spread fire, and that our singular mastery of fire was largely what made us masters over the environment. But it could have worked the other way around, says Bonta. “It could very well have been the case that humans, birds, and fire coevolved in some sort of mutualistic relationship — perhaps humans actually derived the idea of using fire from watching birds. This is what plenty of myths about fire-spreading among indigenous peoples in Australia and elsewhere in the world tell us, after all — birds were the original fire-starters.”
I love this idea: that a bird with a burning stick might upend old Promethean notions of human uniqueness and ecological mastery.”
“Then you see the cause of all the fuss. A seething fan-shaped mass of tens of thousands of army ants boiling across the forest floor. As the raid nears, the noise increases. “You hear the sounds of the critters fleeing from them — harrowed roaches, katydids, crickets, scorpions, big-bodied insects flying, running, hopping to get out,” says biologist Sean O’Donnell. “They’re like animals fleeing a wildfire.”
The ants are Eciton burchellit, 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.
The raid spreads out from a bivouac over the jungle floor, covering every nook and cranny, savage and relentless, scaling trees to attack wasps’ nests, subduing and dismembering large-bodied insects, biting and stinging snakes and other vertebrates, overwhelming even the most vicious scorpions. The prey the army ants take on these raids, as many as 30,000 corpses a day, are carried back in braided lines of workers to feed the 60,000 to 120,000 larvae in their bivouacs.
“The ant colony sends out only a fraction of its worker force because it needs to maintain the integrity of the bivouac,” says O’Donnell, “But the raids can be spectacular, a carpet of more or less continuous ants fifteen to thirty feet wide, advancing through the forest at something like fifteen yards an hour.””
“These ants are not like their counterparts in Africa, which have hooked mandibles. with a knifelike edge designed for cutting through skin and flesh. According to O’Donnell, African driver ants can attack, kill, and eat vertebrates as large as cattle, antelope, and even humans — if they’re drunk or asleep.”
“Male long-billed hummingbirds form leks in the forest understory, where they sing and display for up to eight hours a day. They do this for the entire eight-month breeding season, an extremely demanding effort sustained only by males in excellent physical condition. Dominant males battle over singing perches, sometimes attacking each other with their sharp, pointy bills.
Females visit the leks just once per day, so males must be present and prepared to mate throughout the long breeding season. If they leave to tank up, they risk losing their coveted singing perch, so it pays to know where the nectar-rich flowers are among the thousands of forest blossoms — in order to get there and back quickly. The cost of a single error is probably minimal, says Marcelo Araya-Salas, who studies the hummingbird, but the cumulative cost of making multiple errors during multiple foraging trips each day over 240 days could set a bird way back in its intake of calories.
To explore whether there was a connection between the hummingbird’s spatial memory and its ability to acquire and defend a lek territory — a critical element for mating success — Araya-Salas and his colleagues tested how well males could remember the locations of rewarding hummingbird feeders he placed near the leks. Birds that scored best on these tests turned out to be the dominant males with prime perches at the lek. When it came to holding and defending mating territory at the lek, a good memory for food locations beat out all the advantages of physical prowess — bigger body, bill tip size, even flying power.”
Play
“Doing science with ravens, on the other hand, is easy. “They’re so inquisitive and engaged,” says Osvath. “If they find that a task is interesting enough, they’ll line up to participate. They’re fun to study, and they make me laugh.””
“If one raven was engaging in object play, another might start doing locomotor play, and still others, social play. “It’s the play mood that seemed to be contagious,” says Osvath. Positive emotional contagion is also found in other animal species — chimps and rats, for instance. Scientists have lately found that negative emotions in ravens can be contagious, too. When a raven sees allies struggle with a task that denies them a treat or sees their disappointment in response to unappetizing food — but not the food itself — its own interest in food diminishes. This kind of emotional contagion, whether positive or negative, is considered a building block of empathy.”
“Once kea have learned how to solve a problem or use a gadget, they don’t forget. Schwing brings out a wooden box he used in an elaborate experiment some years earlier to test the kea’s cognitive skills and ability to cooperate. The wooden box is raised on legs and bottomed by a tray that drops down if properly triggered. In the experiment, the tray was loaded with treats — parrot pellets stuck there with cream cheese. Attached to the tray were four separate chains threaded through holes in the side of the box. To release the tray and access the treats, four kea had to pull the different chains simultaneously and continue to pull together until the tray released. If only one bird pulled at a time, the chain would slide out without moving the tray. If any of the birds lets go too soon, the tray would pop back up out of reach.
The results were impressive. Kermit led the way, and after a little training, the other kea quickly learned to pull together and to persist — so they could all get their treats.”
“From 1890 to 1971, the government offered a bounty for dead kea. Methods for killing the birds ranged from poisoned bait to a special kea gun, according to George Marriner, who wrote a book on the bird in 1908. Marriner described kea as “the most inquisitive bird alive” and “a most lively and interesting companion,” and in the same breath, boasted of killing them “at all hours, from the first streak of dawn to the last faint glimmer of daylight.” Before they were finally granted full protection under New Zealand’s Wildlife Act in 1986, more than one hundred fifty thousand kea were slaughtered.”
“If intelligence and innovative foraging are key ingredients in animals that play, so is an extended juvenile period. Kea tick off this box, too, with a very long “childhood” of four to eight years. “That’s incredibly long, even for a parrot,” says Schwing, Kea are not as long-lived as most parrots. An Amazonian parrot will often live eighty or ninety years. Sulphur-crested cockatoos have an average life span of sixty-five years but can live to one hundred twenty in captivity if they’re well cared for. “Kea live only forty years max,” says Schwing. “So even if their juvenile phase is just four years, that’s 10 percent of their maximum life expectancy — that’s a huge amount of time compared to most other creatures.”
“One day, a smaller raven flew in and took a mouse into its crop. As soon as the raven swallowed the mouse, a larger raven, perhaps the nesting female, came down screaming mad at the young raven, who she made disgorge the mouse. She picked it up and took it up to the nest, leaving the smaller raven sitting on the edge of the deck with his head down. She came back down, still screaming, and hit the smaller raven multiple times with her wings along both sides of the head. Another incident of feeding hierarchy in raven groups — the younger raven was clearly supposed to have shared the dead mouse with the nestlings instead of taking it himself and paid the price.”
“To explore the kea calls in the wild as part of his PhD studies, Schwing set up speakers and video recorders at Deaths Corner lookout one cold and dreary winter. He deliberately chose the worst season for the study and went out in the worst weather, gloomy, cold, and drizzly, when no bird in its right mind would be in the mood to frolic. Through the speakers, he played five recorded sounds for five minutes apiece, the warbling play call, two other kea calls; a call of a common bird in the area, the South Island robin; and a simple standardized tone.
The little videos of the results are a hoot. Two adult kea just hanging around on a stone wall, minding their own business in the misty drizzle. The recording of the warbling play call is heard in the background, and suddenly the birds look at each other, burst into squeals, and launch into play, becoming exceedingly silly, chasing each other, flapping up and down, picking up rocks and flinging them, playing hard for the full five minutes of the recording.
“With the warble calls, play just went up drastically,” says Schwing, “500 percent.” Kea of all ages jumped in, with some of the most vigorous and longest bouts in mature adults, including between males and females. Play between fully mature animals of the opposite sex is rare in animals — and if it occurs, it’s usually part of courtship behavior or to strengthen social bonds before a hunt. But in kea, it’s not about food or sex. It’s about play.
The kea didn’t look around for the source of the sound, says Schwing, which suggests to him that the call isn’t so much an invitation, “Come play with me!” as it is an inspiration: “Playtime!” The instant the play call recording stopped, so did the play.”
“Over the course of her time studying kea in the field, she noticed that on a sunny day, after a fresh snowfall, the birds do what we might do — they warbled and played more often than on a gray, rainy day.”
“In the past, New Zealand’s Department of Conservation has dealt with inquisitive kea causing trouble at forestry projects by providing the birds with a ladder to distract them and keep them away from dangerous and expensive equipment. This gave Nelson an idea: build a kea jungle gym by the roadside and make it more appealing and alluring to the kea than the cars, by putting in a variety of toys — swings, climbing frames, ladders, puzzles, and flotation devices — and switching them up a lot, rearranging and refreshing them regularly to hold the birds’ interest.
“The idea is that the kea will be drawn there and so will the tourists who want to watch them and get pictures,” says Taylor. It helps that kea are motivated more by play than food. “If there’s any species in which play and new objects are more important than getting a crisp, it’s kea.”
“The challenge here is to figure out what is essentially catnip for kea in terms of objects they absolutely adore playing with,” says Taylor, “and then somehow to find a constant stream of novel variants of these toys.” The plan is to try to turn this into a citizen science venture, the Great New Zealand Kea Jungle Gym Project, Taylor quips, “and get school kids and anyone else to send us designs for toys they think will be really engaging for kea. And then we could take those designs and build them up and see how the kea interact with them.”
What a fun bit of interspecific reciprocity: people playing around with objects to find suitable toys for kea to play around with. And kea, in turn, providing entertainment for people at play.”
Love
“Consider the sweet-seeming presentations of flower petals by male superb fairy-wrens. Or the tender mutual attentions of Fischer’s lovebirds, those vibrant pint-size parrots native to Tanzania that gave us our expression for openly affectionate couples. 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.”
“At first blush, their reproductive organs seem all alike. Both male and female have a cloaca, an opening that in the male swells during the mating season, projecting outside their bodies. When birds mate, they briefly rub together their swollen cloacae, allowing the male’s sperm to move from his cloaca to hers and then travel up her reproductive tract to fertilize her egg. (Bird cloacae also have a decidedly less sexy role: to excrete urine and feces.)
Most birds have no penis. But there are exceptions. Several species of ducks, geese, and swans have an organ like a human penis, which is inserted into the female. These waterfowl belong to the 3 percent of living bird species that retain the phallus found in their reptilian ancestors.”
“Brennan has found that females have evolved their own rococo genitals, a spiral-like reproductive tract that winds clockwise, in the opposite direction from the male’s penis, and includes up to three branches with blind pockets that make it harder for sperm to reach her eggs. “Female mallards have a say in which sperm fertilize their eggs,” she says. “As many as 35 percent of all copulations with a mallard female are forced by unwanted males, yet these males sire only 3 percent to 5 percent of her offspring.” With a forced copulation, the female keeps her genital tract tight, blocking the male’s lengthy phallus or forcing it to divert down one of those dead-end alleys, so his sperm can’t fertilize her eggs. If she actually wants to mate with her partner, she can relax the walls of the tract and allow his semen passage. She can also eject sperm from her cloaca by defecating right after sex.”
“These birds, which live in the harsh deserts of the Arabian Peninsula, breed in long term cohesive cooperative groups with a dominant pair raising young with helpers that pitch in to feed chicks, defend territory, and ward off potential predators. Ben Mocha found that the dominant pair not only regularly hides its sex from the view of the rest of the birds in the group but also uses some sophisticated cognitive skills to do so. A dominant bird will slip off and head for a spot where it’s visible only to its partner. The bird signals the moment for the meeting by plucking up in its beak some arbitrary object nearby — a stick or eggshell and waving it around at its intended then nodding its head slightly, taking scrupulous care to signal only when no other babbler is looking its way. In one instance, a female was perched on top of a bush and the rest of the group was foraging to one side of it. A male moved to the opposite side of the bush and signaled at the female from there. This suggests that babblers may be able to distinguish their own visual perspective from an alternative point of view — an advanced cognitive skill known as perspective taking.
According to Ben Mocha, the behavior may also entail tactical deception, using a signal or display to mislead or deceive another individual. The object that a male or female babbler picks to use as a signal is most often a small twig or leaf that could well be used for some other purpose, like nest building a way to conceal from the others that it’s actually signaling. When another babbler approaches, the signaling bird drops the object and acts as if there’s nothing interesting going on. “The observing bird cannot know then if it was an invitation for mating or, for example, searching for nesting materials,” explains Ben Mocha.
Once a babbler receives the signal and decides to cooperate, the two birds sneak away together — when no one else is watching to copulate behind a bush or tree. Then they’ll hop back onto the scene seconds later “in a very normal way,” Ben Mocha explains.”
“Levick noted that Adélie penguin males claim a territory, gather rocks to build a nest, and when the females arrive, are thrown into a kind of frenzy. They toss back their heads, beak to the sky, and discharge a string of hoarse trills and squawks, “a volley of guttural sounds straight at the un-responding heavens,” he writes, “a Chant de Satisfaction.” Then come a male’s overtures to a hen. “He would, as a rule, pick up a stone and lay it in front of her . .. rise to his feet, and in the prettiest manner edge up to her, gracefully arch his neck, and with soft guttural sounds pacify her and make love to her. Both perhaps would then assume the ‘ecstatic attitude,’ rocking their necks from side to side as they faced one another, and after this a perfect understanding would seem to grow up between them, and the solemn compact was made. It is difficult to convey in words the daintiness of this pretty little scene.””
“Levick had no context for the penguins’ behavior. The truth is, plenty of birds interact sexually with dead members of their own species. The behavior has been noted in bridled terns, European swallows, sand martins, and Stark’s larks. It’s not at all the same as a human having sex with a corpse and can be explained in the context of our modern understanding of animal behavior.
Well, sort of.
There’s even a term for it, Davian behavior, coined by Robert Dickeeman — known as the biologist who gave necrophilia a good name. Dickerman speculated that the “lordosis” posture of a dead ground squirrel, with back arched downward, might release the copulatory drive in a sexually aroused male. And indeed, when biologist David Ainley conducted an experiment on Adélies with a dead female penguin frozen into position, he noted that older males found the female corpse irresistible.
However, a recent study of the interactions between wild American crows and dead birds challenged the idea that inappropriate mating attempts are triggered by the stimulus of copulation posture. It’s not so simple. Kaeli Swift and John Marzluff found that during the breeding season, crows also tried to mate with a lifelike crow in a neutral standing position and with a crow lying on the ground in a “dead” position, its wings tucked close to its body — the latter effort accompanied by plenty of scolding. Maybe it’s not the copulation position per se that inspires arousal, say the scientists. A dead posture excites alarm, which is not uncommonly followed by sexual behavior. This sex-after-alarm response has also been noted in zebra finches, vermilion flycatchers, and pied avocets. Swift and Marzluff point the finger at hormones. “It may be that breeding-related endocrine changes downregulate the ability of some birds to process conflicting information.””
“For heroic physical prenuptial feats, few birds outdo the male black wheatear, a small species that breeds in cliffs and stony slopes in western North Africa and Iberia. These one-and-a-half-ounce birds ferry in flight an average of four pounds of stones to waiting females in nest cavities in caves and cliffs. That’s like a one-hundred-fifty-pound human carrying ten thousand pounds of stones. A single male may carry in his bill as many as eighty stones in a half-hour period. He does so in part to build a base for his nest but also to impress his mate, showing off his strength and the potential quality of his paternal care.”
“Take lance-tailed manakins, birds that breed at dispersed leks in Central and South America. They have this “strange, amazing, different, and complex form of cooperation,” says DuVal. To attract females, an alpha and a beta male perform tightly coordinated male-male duets and dance displays with eleven unique elements, ranging from slow butterfly flights with wing clicks and “pip flights” — quick circlings of the perch accompanied by pip calls at landing — to leapfrog dances, vertical bouncing, and back-and-forth hopping. “What you expect to see in lekking birds is intense competition,” says DuVal, “and here you get a situation where males work together in cooperative partnerships that may last as long as six years.””
“We humans are constrained not just by our limited senses but also by our perception of time. In the bird world, things happen fast, sometimes too fast for us to see. To make this point in talks, Mike Webster of the Cornell Lab of Ornithology shows a real-time video made by biologist Lainy Day of a male black manakin displaying in the forests of Guyana. In the film, the male manakin looks like it’s simply hopping up and down. Then Webster plays Day’s high-speed video, which shows hundreds of frames per second, as the female manakin would see it. Jaws drop, and there’s an audible gasp from the audience. Between the little hops, the male completes a full-body, 360-degree flip, a high-speed somersault too quick for us to see.”
“Ornithologist Alec Chisholm noted that one bower in New South Wales held more than 1,300 bones. “Imagine the strength of the decorative impulse that caused a bird to carry in its beak, one by one, and over long distances, that large number of sturdy bones,” wrote Chisholm. He also marveled at the 2,500 snail shells he discovered in and near another bird’s bower, “each somewhat bulky relative to the size of the bird’s beak,” and nonetheless carried over considerable distances.”
“In composing their jazzy high-intensity song and dance, experienced males may take into consideration the sensitivities of the female they’re courting and modulate their performance to lessen the threat, alternating between forceful and softer elements.”
“In the experiment, each female was offered the companionship of two males to see which she preferred. Then the researchers spent a week training the “less preferred” male on a foraging puzzle teaching him to open a tricky translucent container full of seed. Next, each female was allowed to watch the trained but previously scorned) male handily solve the puzzle again and again, and in between, to watch the untrained (but previously favored) male be completely stumped by the task. The females had in their compartments their own seed-filled puzzle boxes taped shut so they were aware of the difficulty of the task at hand. After the observation period came the moment of reckoning. The females were once again asked to choose between the two males. Remarkably, they all shifted their preference to the males they had once rebuffed but that had shown themselves to be adept problem solvers.
This would seem to be a clear-cut example of the “smart is sexy” idea.”
“Exclusive monogamy in a bird pair is actually considered noteworthy. Among the handful of true monogamists are mute swans, black vultures, scarlet macaws, bald eagles, Laysan’s albatrosses, whooping cranes, California condors, and Atlantic puffins.”
Parenting
“A male brush turkey spends nearly three months building his mound, raking up two to four tons of leaf lit ter and soil to create a massive conical structure roughly the size of a car, three or four feet high and up to twenty-two feet in diameter. All of this effort he exerts for a single purpose: to create an incubator for his eggs.”
“The smallest nest on record is the bee hummingbird’s, a wee inch in diameter, and the largest, a bald eagle nest in Saint Petersburg, Florida, that was ten feet wide and twenty feet deep and weighed close to three tons.”
“Beware entering the range of a magpie with chicks. Most Australians have learned this the hard way. Some 85 percent have been attacked at some point in their lives.”
“The birds swoop in, often from behind, and hammer your head, neck, and face with their powerful beak and scratch with their claws. Injuries are common, usually minor cuts and scratches, but sometimes more serious harm occurs — broken limbs or damaged eyes. “There are thousands of people injured every year,” says Jones. “People have terrible accidents on bikes. And every year eyes are lost. So it’s a genuine issue.””
“The swoopers are almost always male. And only certain males are hyperaggressive in this way, says Jones-around 10 percent. “If it were higher than that, I don’t think Australia would be habitable.” Males swoop only when chicks are in the nest, a period of about six weeks, and then the swooping stops abruptly.”
“The magpies seem to specialize. Around 50 percent of them are pedestrian magpies — they only swoop pedestrians. Cyclist magpies swoop only cyclists. And then there are magpies that specialize in hammering posties — the postal workers on little motorbikes that go whizzing up the street, postbox to postbox. In his research, Jones found that magpies that attack cyclists will attack any cyclist. And those that attack posties will attack any postie.
“We think the cyclist and postie magpies are generalizing,” says Jones. He believes it has something to do with speed. “They’ll be coming after you, and if you stop and get off the bike and walk it, they sort of look around as if to say, ‘Where is that fast thing that I was just chasing?’”
“None of this stopped Australians from voting the magpie their favorite bird, beloved for its early morning caroling, described as a “quardle ardle oodle” or “wad-de giggle gargle,” depending on whom you ask — though neither phrase captures the marvelous musicality of the bird’s song. Magpies can be very tame and are often kept as pets.”
“As for the anomalies and special cases: Those penduline tits that collaborate to make their teardrop nests seem to have an oddball parenting system. Either the male parent or the female parent may desert the nest during the egg-laying phase, leaving the remaining partner in sole charge of the young. In a whopping third of cases, both parents desert the nest, abdicating all parental care.”
“In the case of the eclectus parrot, the roles of male and female have diverged so much — the one being purely defensive and the other purely about foraging — that they have completely different selection pressures working on them. This is why they break all bird coloration rules. “Their extreme reversed coloration is not linked with reversed sex roles but instead with stiff competition for rare nest hollows,” says Heinsohn. “It’s all about scarcity.”
Females evolved a brilliant vermilion plumage, visible for miles against the leafy green branches, that acts as a gaudy beacon to other females, saying, “This hollow is occupied!” Males, on the other hand, evolved plumage of a rainforest green on their backs, which offers camouflage protection from aerial predators while they forage for themselves and their mates.”
“The bizarre behavior sometimes observed in mothers — killing their sons just after they hatch — also arises from the shortage of hollows. Not all nesting hollows are created equal, says Heinsohn. There are dry ones, which are great for breeding, and there are poor ones with a tendency to flood in heavy rain, drowning eggs and chicks. Female eclectus chicks generally fledge up to a week earlier than males, so mothers stand a better chance of successfully reproducing by pouring all of their maternal efforts into female chicks. If a female nesting in a flood-prone hollow hatches a male and female chick, she will get rid of the male chick in order to speed the development of his female sibling. And because the chicks come out of the egg with their gender color differences, mothers can decide their fate within hours of hatching.”
“Which is where the male brush turkey’s secret talent comes in: Every morning, he excavates a narrow hole at the base of the mound and thrusts his head into the warm material to take its temperature. He can detect the slightest shifts in temperature and manipulate it by adding or removing fresh, damp vegetable matter, holding the temperature of his incubating eggs very close to the optimum of 91 degrees F.”
“When they’re ready to hatch, the chicks use their backs and feet to bust through their shell.
What happens next is miraculous: The chicks hatch into a dark, damp, suffocating world, entombed — quite literally — under tons of stuff. There’s little oxygen and plenty of toxic carbon dioxide. “They start life at the bottom of a meter of dirt and sticks and rocks,” says jones, Each chick lies on its back and, using its feet, scrapes at the material above, compressing the dislodged stuff beneath its back. It spends as long as two and a half days doing this, digging upward little by little, struggling through the dense dirt and litter of the mound, pausing frequently to recover.
When the baby bird finally breaks into the light of day, it pops out as the most advanced chick of any bird species, instantly able to fend for itself, to run, feed, and fly. “Brush turkey chicks are so super precocial they almost require their own terminology,” says jones. They need to be. You would think after all this that the chicks’ father might be waiting with a mouthful of food. But no. He’s actually a threat. “If a chick is unlucky enough to meet Dad on the way out,” says Jones, “he has no idea what the chick is. It’s just some horrible thing in his mound. And — I’ve seen this many times — he just boots it off into the bush.”
The chicks survive this paternal hurling. What they don’t survive — and this is the absolute cost of having no parental care, says Jones — are the cats and dogs and foxes and goannas and everything else around the place intent on eating them. “There’s no parent to tell them what a predator looks like, what’s an appropriate behavior if a cat comes up, how to hide, what to do.” Some 97 percent of brush turkey chicks don’t make it through the first week.”
“In the woodlands of northern Mozambique, a Yao honey hunter moves through the bush, uttering a. loud call, a brrr trill, followed by a short hm! At first, nothing. But then out of the trees a wild bird about the size of a starling appears. Dark backed, with a pale breast, it approaches the hunter. What ensues is a kind of collaborative treasure hunt. The bird, a greater honeyguide, responds to the hunter’s call with its own distinctive chattering call that differs from its territorial song, a sharp tirr-tirr-tir, as it flies from tree to tree, leading the hunter through the forest. It flits from perch to perch, emitting its persistent call. The hunter follows. This pattern of leading and following is repeated until the bird reaches the treasure: a nest of bees ensconced high in a broad-leaved tree or tucked into a rock crevice or termite mound. Once close to the nest, the honeyguide perches nearby and lets out an “indication call,” softer in tone, with longer pauses between notes.”
“In this way, birds and humans communicate. “The honey-hunters use these special calls to signal honeyguides they’re eager to follow, and honeyguides use this information to choose partners who are likely to be good collaborators,” says Spottiswoode. It can work the other way, as well, with a bird initially summoning human partners with its special loud chattering come-hither call.
The bird literally points the way to hidden bee nests; from its calls and its flight and perching pattern, the honey-hunters construe the direction and distance to the nest. After the hunters harvest the honey (subduing the bees with smoke), they leave the energy-rich honeycomb wax for the birds to feast on.
The greater honeyguide earned its Latin name Indicator indicator from this unique and probably ancient cooperative relationship with African honey-hunters, first confirmed by Kenyan ecologist Hussein Isack in the 1980s. Both parties benefit, fair and square. The birds, which specialize on a diet of beeswax, can’t get at much wax without the hunters’ help subduing the bees and opening their nests, and the hunters often need the help of honeyguides to quickly and efficiently find the nests — an important source of calories for them.
As far as we know, no other wild animal collaborates with humans in such a direct way. “Of all the relationships between people and wild animals,” writes Flizabeth Pennisi in the journal Science, “few are more heartwarming.” Heartwarming from a human perspective, perhaps. But honeyguides are Jekyll and Hydes. Less touching is their penchant for siblicide, for murdering their stepsiblings in the dark nests of their adoptive parents.”
“Greater honeyguides are brood parasites, those good-for-nothing moms and dads at the zero parenting end of the bird spectrum. Females lay their eggs in the nests of other species and trick the unwitting host parents into raising the parasitic nestlings, often at the expense of their own young.”
“Greater honeyguides often target as their host the little bee-eater, a beautiful cinnamon bird about the size of a sparrow, with a bright green backside and yellow throat. It nests in narrow tunnels dug into the roof of much larger holes excavated by aardvarks. The female honeyguide incubates her egg inside her body for an extra day before dumping it in the bee-eater nest. This means that her chick will hatch ahead of the host eggs, the better to ready itself for what comes next: murdering its nest mates. The weapon is a pair of needle-sharp hooks at the tips of the chick’s beak, which it uses to stab its foster siblings one by one as they hatch.”
“Parasitic chicks have other tricks up their sleeves. To dupe their host parents into bringing them more food, chicks of the Horsfield’s hawk-cuckoo, an Asian species, flash bright yellow patches beneath their wings when their host parents feed them. The wing patches look just like the gaping mouths of extra chicks and also brilliantly reflect ultraviolet light, signals that together make for an irresistible stimulus to host parents to feed the cuckoo nestling more than the standard chick rations. If all goes according to plan, the parasitic chick, gleaning the usual feedings, plus some, grows and grows, sometimes to monstrous size compared with its host parent. The sight of a European wren perching on the back of a giant common cuckoo chick ten times its size in order to get food in its mouth, or a petite white-plumed honeyeater struggling to satisfy the appetites of the massive pallid cuckoo chick overflowing its nest is among the strangest in nature and tears at the heart.”
“When a female cowbird finds a nest and the timing isn’t quite right for her to lay, she may destroy the egg clutches and broods, forcing the hosts to start over so they’re in synchrony with her schedule. The chicks that hatch from her eggs don’t normally toss out the host young that share their nest, but they do compete vigorously with them side by side. Many of the smaller host chicks don’t stand a chance against the cowbird chick and end up dying of starvation.”
“For their hosts, the brown-headed cowbird is nothing short of a nightmare. Researchers recently found that a cowbird female will closely observe the nests she lays in, and if the hosts eject the foreign eggs, she may wreak havoc on the nest and savage the eggs by puncturing them — possibly to force the hosts to build a new nest, the better to parasitize it, a strategy called “farming.” Or possibly in revenge, punishing the hosts by destroying their nest and the entire clutch within it. These mana-like tactics may explain why some host birds don’t oust the cowbird’s parasitic eggs. A host may learn that if it doesn’t play the game the cowbirds’ way, the parasites may come back and badly mess with their nests.”
“The cowbirds are good at what they do-so good that they appear to be contributing to the demise of dozens of already troubled North American songbird species on the brink of extinction from habitat degradation, including the endangered least Bell’s vireo and the Kirtland’s warbler.”
“This process of reciprocal adaptation gives rise to some astonishing results.
For one thing, cuckoos around the world have evolved superb egg forgeries. Their hosts, in turn, have evolved such exceptional powers of discrimination that they can spot a cuckoo egg that’s almost completely identical to their own, with just the tiniest discrepancies. It’s a sophisticated learning process less about spotting the odd egg in their nest and more about learning in detail the look of their own eggs.
Some host species have evolved an additional defense: eggs with a unique pattern of spots and squiggles that varies from female to female. Mary Caswell Stoddard and her colleagues recently explored how several species of British songbirds that are targets of the parasitic common cuckoo might fight back against cuckoo egg mimicry with specially patterned eggs. “If hosts are having a hard time fighting cuckoos,” she says, “one way to make the job easier is to evolve a complicated and really recognizable pattern that allows you to say, ‘That egg is mine.””
“If a common cuckoo or a cuckoo finch gets its egg into the nest of a brambling or an African prinia, and the egg passes muster, the brood parasites are all set. The hosts of common cuckoos almost never reject cuckoo chicks – even though they look nothing like host young. Even a few weeks after hatching, when a cuckoo chick is more developed, the host birds are strangely incapable of identifying the little monsters that have hijacked their nest, and will care for “Rosemary’s baby” until it fledges.
There’s a theoretical model suggesting why this is so. Bird parents “imprint” on the chicks that hatch from the eggs in their very first clutch, and after that, reject any chick that’s different. Host parents that are unlucky enough to be parasitized in their first clutch will imprint on the cuckoo chick and rebuff their own young forever after.”
“In Australia, not only do the hosts break the rules, so do the cuckoo chicks. “Because of this good recognition ability in hosts, cuckoo chicks have evolved wonderful mimicry of host young, either in appearance or in begging calls, which you don’t get anywhere else.” The bronze-cuckoos, which target fairy-wrens, thornbills, and gerygones, she says, “have evolved these fantastically matching chicks that mimic the size, the skin color, the down color, even the mouth color of the host species.
Horsfield’s bronze-cuckoo chicks even sound like the host young, learning over time to match their begging calls. “This is pretty remarkable when you consider they evict the host chicks before they ever hear their calls,” says Langmore. “They seem to attend to what sounds make the host parents most responsive and rapidly modify their begging calls over several days until they’re virtually indistinguishable from the calls of the host young” — an extraordinary form of learning.”
“As for the evolution of counter-strategies in cuckoo hosts: Diane Colombelli-Négrel, a researcher at Flinders University in South Australia, and her colleagues discovered that fairy-wrens fight back against the cuckoos’ begging-call mimicry in an ingenious way: They give their young a chance to learn a password while they’re still in the egg.
Both superb and red-backed fairy-wren mothers produce special calls while they’re incubating their eggs, singing them over and over, the same tune every few minutes. The calls contain a unique note that acts like a familial password, which the embryonic chicks commit to memory. Dads learn the passwords, too. After the chicks hatch and begin to beg for food, they reliably include that signature note in their begging calls, so their parents know, “Aha! That chick is mine.””
“”It would make sense from an evolutionary standpoint that host species in different parts of the world have converged on a common cuckbo alarm call,” says Feeney.
“Cuckoos are a unique kind of superweird threat — they’re no danger to the adults, just to the young. So in thinking about the evolution of alarm calls, you ask, ‘What are the pressures?’ In response to a predator like a pied currawong, a bird has to walk that line between sounding the alarm and being spotted by the predator. ‘I want my friends to know about this threat, but I don’t want it to know about me.’ Whereas with cuckoos, all bets are off, and you just want everyone to know about it and come in and kick the living hell out of that cuckoo. If that’s the case, you’d expect selection to favor basically the loudest, most annoying sound you can come up with, with the highest chance of bringing in as many species as possible.”
What does the call sound like? A sort of high-pitched whine. Imagine if a seahorse could neigh.”
“Like anis, female acorn woodpeckers that find an egg in their nest before they begin laying will destroy it, a practice that results in the demise of more than a third of all laid eggs. But, as Koenig and his colleague Ron Mumme discovered, the smashed eggs don’t go to waste. The woodpecker group takes all the egg debris to a tree and feasts on it together, including the females who laid those eggs. Mumme calls this “communal egg sucking.”
The female ani that lays an ejected egg doesn’t resist the displacement. “She neither attempts to guard her eggs nor retaliates against the female that evicted it.””
“Sometimes the advantage or the necessity of a large group is so great that birds actually kidnap the young from other groups to boost their numbers. Cue the white-winged chough.”
Conclusion
“I’ve just learned that nesting veeries are better than meteorologists at predicting the severity of an upcoming hurricane season. Ornithologist Christopher Heckscher discovered that veeries nesting in Delaware cut short their breeding season in years with the most numerous and intense hurricanes. Months in advance, they anticipate the storms and adjust their migratory schedules for crossing the Gulf of Mexico and the Caribbean Sea on their migration to South America to avoid the worst of the hurricanes. They also lay more eggs earlier in the season. How these birds know in May what will happen in August is a deep mystery, probably having to do with cues they pick up during their wintering season in South America. In their ability to predict the tropical storm season to come, the timing of nesting veeries is at least as good as — maybe a bit better than — the predictions by weather forecasters at the National Oceanic and Atmospheric Administration. Female veeries, that is. They’re the ones that decide on the nesting and egg-laying schedule.”
“Just before his death in 2009, the world’s leading expert on species associated with army ants, Carl Rettenmeyer, completed the first comprehensive list of animals known to keep company with Eciton burchellit, the “mini-lion” of neotropical forests. Rettenmeyer recorded 557 species in consort with the ants, ranging from mites and insects to a huge variety of birds. It’s the largest group of animals ever described centering on a single species. At least 300 of these species depend on the ants, including the charismatic ocellated antbird. The disappearance of Eciton burchelli from any habitat over their vast range would trigger the extinction of hundreds of birds and other animals.
It can happen fast. Over the past decades, ornithologists have found that birds that depend on insects for sustenance are rapidly declining. Gone from European farmlands and countryside are little owls, bee-eaters, Eurasian hobbies, and eight species of partridges. Populations of nightingales and turtledoves are greatly diminished. The culprit is not habitat destruction but starvation from the disappearance of their primary diet — beetles, dragonflies, and other insects.”
“That same year scientists delivered the shocking news that one in four birds in the US and Canada have disappeared since 1970 — nearly three billion birds. The vanished species span the spectrum from meadowlarks, warblers, and swallows, to common backyard birds such as robins and sparrows. They’re gone from all habitats, seashore, forest, grasslands, desert, tundra, probably due primarily to habitat loss from development and agriculture, as well as pesticide use.”
“On the drive back to Lund from his farm in Sweden, Mathias Osvath offered some perspective from his work with birds, only partly tongue-in-cheek. Corvids, he believes, are at the brink of a cognitive breakthrough. They have been around for millions of years. We humans have existed as a species for at most a few hundred thousand years — in geological terms, a flash in the pan, statistically insignificant. But in the short time of our existence, crows, ravens, and other corvids have learned to use us as a source of food and shelter. If our species disappears and corvids lose this resource, there may be selective pressure among them to boost cognition, says Osvath. Their brains could double or triple in size, and with their superefficient signaling and tight packing of neurons, they might become the next big thinkers, dominant among animals. It could happen very quickly, he says. “We dig up dinosaurs to try to figure out what happened to them. Perhaps someday dinosaurs in the form of corvids will dig us up to figure out what happened to us.” He hopes they won’t repeat our mistakes.”
