Thinking like a Parrot

Perspectives from the Wild

Alan B. Bond, Judy Diamond

• Publisher: University of Chicago Press
• Year: 2019
• ISBN:
  9780226248813
• Topic: Biowissenschaften
• Subtopic: Wissenschaft Allgemein

From two experts on wild parrot cognition, a close look at the intelligence, social behavior, and conservation of these widely threatened birds. People form enduring emotional bonds with other animal species, such as dogs, cats, and horses. For the most part, these are domesticated animals, with one notable exception: many people form close and supportive relationships with parrots, even though these amusing and curious birds remain thoroughly wild creatures. What enables this unique group of animals to form social bonds with people, and what does this mean for their survival?In Thinking like a Parrot, Alan B. Bond and Judy Diamond look beyond much of the standard work on captive parrots to the mischievous, inquisitive, and astonishingly vocal parrots of the wild. Focusing on the psychology and ecology of wild parrots, Bond and Diamond document their distinctive social behavior, sophisticated cognition, and extraordinary vocal abilities. Also included are short vignettes—field notes on the natural history and behavior of both rare and widely distributed species, from the neotropical crimson-fronted parakeet to New Zealand's flightless, ground-dwelling k?k?p?. This composite approach makes clear that the behavior of captive parrots is grounded in the birds' wild ecology and evolution, revealing that parrots' ability to bond with people is an evolutionary accident, a by-product of the intense sociality and flexible behavior that characterize their lives.Despite their adaptability and intelligence, however, nearly all large parrot species are rare, threatened, or endangered. To successfully manage and restore these wild populations, Bond and Diamond argue, we must develop a fuller understanding of their biology and the complex set of ecological and behavioral traits that has led to their vulnerability. Spanning the global distribution of parrot species, Thinking like a Parrot is rich with surprising insights into parrot intelligence, flexibility, and—even in the face of threats—resilience.

PART ONE

Origins

. . .

1

Rainbow Lorikeet

. . .

Trichoglossus moluccanus

In northeastern Australia, Barringtonia trees along the esplanade in the city of Cairns are magnets for rainbow lorikeets, small parrots specialized as nectar feeders (fig. 1.1). The trees have broad, glossy leaves and bear pendulous chains of creamy white flowers that produce huge quantities of pollen and nectar. Lorikeets descend onto the Barringtonias in the early morning: the birds dangle on the flower chain by one foot, stretching far down the stalk without disturbing the blooms (plate 1). They then work systematically back up the inflorescence from the tip toward the base, grasping each flower in their beaks and sweeping their tongues around the floral cup.

Lorikeets are methodical, processing flowers at a furious pace: One bird can harvest over a thousand flowers in less than an hour. Although they occasionally feed on fruits, insects, and even seeds, lorikeets mainly make their living from nectar and pollen. They have an advantage over other parrots: many Pacific and South American species feed on flower nectar, but few can digest the pollen grains and extract their protein-rich contents. Lorikeets have specialized digestive systems that allow them to exploit this resource. Their long stomach gives the pollen a luxurious acid bath that effectively breaks down the tough grains.

Lorikeet tongues are spectacularly extensible. They are able to reach out to nearly twice the length of the bill, giving the birds the appearance of feathered chameleons. Their tongues terminate in a dense array of fine papillae that form a brush-like appendage. The brush retracts below the front edge of the lower bill when the bird is feeding on hard or fibrous food. But when a lorikeet extends its tongue and thrusts it into the throat of a flower, the brush tip emerges and expands to draw in nectar by capillary action.1

Rainbow lorikeets may be fast and proficient, but their preferred foods are attractive to competitors, so they have to contend with an entire zoo of other animals vying for the same sweet and nutritious resources. The lorikeets in the Barringtonia confront large wasps and day-flying moths as well as other small birds, like brown honeyeaters, that cling to the inflorescence and expertly dodge any efforts to drive them away. Toward the end of the day, hordes of fruit bats begin to assemble on the tree and poke their noses into the flowers.

Beautiful as ballerinas and efficient as machines, these small parrots are as fierce as wolverines when it comes to other lorikeets. The abundant resources, concentrated in a limited spatial area, bring out the worst sort of belligerence toward other members of their species. Rainbow lorikeets have a particularly short fuse, and they frequently interrupt their nectar drinking to threaten others, replacing their continuous buzzy “zik” calls with squawks and harsh chatters. When necessary, they deliver a ferocious bite, driving the interlopers out of the tree. Lorikeets form loyal pairs that forage together and cooperate in their aggressive displays to chase intruders from their flowers.2

Rainbow lorikeets occur historically in Indonesia, the Solomon Islands, Vanuatu, New Caledonia, and along northern and eastern Australia. Their unusual feeding adaptations allowed them to spread widely among the southwestern Pacific Islands. On the mainland, their populations are expanding along the humid coasts of Australia and into suburbs and cities, where they decimate backyard fruit trees and grape crops. They have been declared pests in western Australia, where large flocks have naturalized from a few pairs that escaped or were released in the 1960s. Their aggressive behavior protects their food resources and helps to secure nesting cavities. Lorikeets generally lay their eggs in the hollows of mature trees, but they have been known to build nests on ledges, on the base of palm fronds, and rarely, even in holes on the ground.3

Toward late afternoon on the Barringtonia, the pace of the lorikeets’ frantic foraging begins to abate. The parrots lose interest in stuffing themselves and start snuggling in pairs, engaging in long bouts of mutual grooming, running their bills through each other’s feathers. The bouts are precarious, and the grooming periodically degenerates into squabbling. A bird suddenly shoves its partner with one foot, receiving a bite in response. And then just as suddenly, they return to grooming each other, as if they had always been the best of friends.

As night approaches, the lorikeets depart in groups of twenty or more. As if changing shifts at a factory, the mammals move in: fruit bats begin to edge their way onto the Barringtonia, which will soon be blanketed with these furry competitors. Less than a hundred meters away, a golden rain tree begins to vibrate, weighed down by hundreds of roosting rainbow lorikeets complaining and snapping at each other. After dark, the birds gradually shift to quiet grooming, and the roost tree falls silent.

2

Evolution

. . .

Humans have a special fondness for parrots. Their appearance is unlike that of any other bird—exaggerated and comical, suggesting good humor and mischief. Their large, round eyes are often accented with rings of bright colors that resemble clown makeup, and their overlapping bills can appear as innocent smiles. Their forward- and backward-pointing toes, which enable them to clamber through treetops with ease, give them an endearing waddling gait on the ground, rather like a child learning to walk.

Parrot behavior in captivity is unpredictable, alternating affectionate attachment with fierce aggression and a manic demolition of any available object. They are adept mimics of both human speech and common household noises, and they often vocalize in appropriate contexts, as if they intuit human feelings and comprehend language. But these moments of linguistic expertise are interleaved with apparently mindless squawks and chatters and occasional penetrating shrieks. It is inevitable that people should sense in these birds a familiar presence, a distorted mirror image of themselves: little, green, feathered people with a will of their own—clever, manipulative, capricious, rather like leprechauns. Through a fluke of nature, a peculiarly human intelligence seems to have been transplanted into the body of a bird.

And the parallels are numerous: parrots, like people, have large brains for their body size, suggestive of intelligence. Parrots, like people, live in structured social groups, with relationships that extend well beyond their nuclear families. And like people, parrots develop innovative foraging methods and readily tackle and solve difficult environmental challenges. Their social relationships enhance their ability to learn new tasks and discover new resources. And most impressively, like young humans, parrots from an early age acquire an ability to communicate vocally and to form long-term relationships with their friends and caregivers.

Lewis Carroll’s Through the Looking Glass begins with Alice sitting in her parlor stroking a cat and contemplating what might be found in the world she can see through the mirror above her fireplace mantel. What she sees at a glance is a reversed image of the room she is standing in, the same boring stuffed chairs and Victorian tables. But what if she could go through the mirror and see what was visible on the other side, in the parts that are out of her normal view? She discovers that she can, in fact, pass through the mirror, but the other side is not what she expects. The clock in the mirrored room has an animated face; all the pictures are alive; and down on the hearth, live chessmen are marching up and down among the ashes and holding paradoxical conversations. The language of looking-glass characters seems familiar, but the meaning of their words is confusing. Inside the mirror is not just a replica of Alice’s world but an alternate reality, governed by entirely new rules and logical systems.1

If, like Alice, we pass through the mirror that distorts our view of parrot behavior and examine the birds from their own perspective, they seem less like little people and more like a distinct evolutionary innovation. Their sensory systems operate strangely: they use their tongues to feel, rather than taste, the texture of food. They see a broad range of colors, but their two eyes provide independent views of the world. They are sensitive to subtle features of sounds but poor at localizing them. They forage, breed, and roost in groups that constantly change their composition, coordinating their movements using a wide array of baffling vocal signals. The way that they go about solving problems suggests a different kind of intelligence that is both practical and original. In captivity, parrots have an unmatched facility for interacting with humans, which makes it hard to appreciate how completely their predispositions and abilities were shaped to fit their lives as wild birds.

The silhouette of modern-day parrots is unmistakable: their rapid wing strokes and foreshortened faces mark them out even in distant flight against a darkening sky. When feeding in trees, parrots can be almost invisible, their green and yellow feathers blending into the surroundings. Even pure white or black parrots readily disappear into the shadows of heavy foliage. Their cryptic appearance is surprising because parrots display a wider range of colors than other bird species, painted with an entire artist’s palette. The bright colors of many birds are derived from their diets, but the reds, yellows, and greens of parrot feathers are independent of their food. They are produced by a singular class of pigments called psittacofulvins, chemicals synthesized only by parrots and found only in their feathers.2

Parrot upper bills are robust, deeply curved, and sharply pointed (plate 2). Their lower bills are shorter and bear a sharpened edge, the tomium, which slices upward and forward against the anvil of the upper jaw like a knife on a cutting board. Parrot jaw muscles, aided by a kinetic skull with a true hinge joint, produce a powerful bite that crushes nuts and chisels hard wood. The hinge joint incidentally allows them to use the upper bill as an anchor when climbing the trunks of trees or sidling along branches.

Parrots use their impressive jaw apparatus as a multipurpose tool to hold food, shred plant fibers, break into tough fruits, crack hard seeds, dig in the soil, and in the case of omnivorous parrots, tear apart animal flesh. They maneuver their food into chewing position with a large, fleshy tongue, which in some species, narrows to a keratinized tip resembling a fingernail. This prehensile tongue stabilizes food items between the knife of the tomium and the cutting board of the upper bill.3

The feet of parrots are zygodactyl, meaning that the two central toes point forward and the two outside toes point backward, so like climbers with crampons, they can walk straight up vertical inclines. Parrots are not the only birds with this foot configuration, but all parrots have it. The arrangement of their toes is so flexible they can grasp everything from large branches to tiny berries, and they hold things to be examined or consumed in what is essentially a fist (fig. 2.1). To varying degrees, all modern parrots have retained this same primary suite of unique characters. They reflect a specialized lifestyle that proved so successful that the traits became deeply imbedded in the parrot genome.4

Ancestry

. . .

As stegosaurs and allosaurs wandered through Jurassic forests, feathered dinosaurs glided above them. An asteroid collision about sixty-five million years ago ultimately killed off many of the large reptiles. But the feathered therapod ancestors of modern birds survived the chaos, leaving a thin thread of descendants. This meager branch of the tree of life subsequently flowered in an explosive radiation of all major groups of modern land birds, possibly the fastest large-scale diversification in the vertebrate fossil record.5

During the early Eocene, about fifty million years ago, Earth’s land masses only vaguely resembled their modern configuration. The continents were closer together, Europe and North America were connected, and the supercontinent of Gondwana was scattered in large pieces across the Southern Hemisphere. Over much of the world, the climate was like today’s tropics—warm, wet jungles of the broad-leafed relatives of modern figs, magnolias, cashews, avocados, pawpaws, and mangoes. The survival of these tropical trees was closely bound to the birds that consumed their fruits and spread their seeds. In this abundant garden, tree-living birds thrived and multiplied into new forms. These were the evolutionary lineages that led to modern rainforest birds, and among them, there were ancient proto-parrots. Proto-parrots would have been hard for a time-traveling field biologist to recognize, since they lacked many of the features that identify parrots in modern guidebooks. These strange birds had distinctively zygodactyl parrot feet, but their skeletons showed little indication of a modern parrot’s large, rounded skull or shearing bill. The bills of Eocene proto-parrots were shallower, more like today’s rollers or trogons, suggesting they mainly ate fruit or leaves.

2.1 This brown-hooded parrot shows a characteristic lateralization in feeding, preferentially holding items in its left foot. Laguna del Lagarto, Costa Rica. Photograph by J. Diamond.

Earth’s climate went through an abrupt shift at the end of the Eocene about thirty million years ago, becoming muc...