Humming Along


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Some hummingbirds are no larger than a thumb, and the smallest among them are the very smallest birds in existence. Yet it’s hard to avoid superlatives when talking about these tiny creatures. With their often magnificent jewel-like colors, they glimmer like finely wrought works of art. In fact, they are miracles of nature: extremely agile, fast-moving animals that take the characteristics of birds to their utmost limit. Combining dynamism, fragility, and a surprising degree of fearlessness, hummingbirds can be found in the most diverse environments: in tiny front yards in North, Central, and South American cities; on the high plateau of the Andes; and in the dense Amazon forests.

The very first mention of hummingbirds by a European probably occurred in the accounts of Jean de Léry, a French sailor and explorer. De Léry was part of a group of mariners sent to the Brazilian coast in 1556. His 1557 Histoire d’un voyage fait en la terre du Brésil, autrement dite Amérique contains a number of observations about the inhabitants, flora, and fauna of this new continent, completely unknown to the readers. Throughout the two centuries after de Léry, a range of authors mentioned hummingbirds, but a systematic framework for their observations was still a long way off. George Marcgrave, who traveled to Brazil in 1638, described several hummingbird species in his Historia Rerum Naturalium Brasiliae, published in Amsterdam ten years later. Soon the birds were popping up in all sorts of contexts — their unusual features were always worth an anecdote. In his Mundus Mirabilis Tripartitus (1689), one of the compendia of all sorts of natural curiosities popular at the time, the German Eberhard Werner Happel speaks of a “little bird in its shining little plumage” that lives in the “New Netherlands”:

It is barely the length of a thumb and sucks from the flowers like a bee …. Another type of this most beautiful bird is found on the islands of the Antilles, but especially on the island Anegada. Its body is not much larger than that of a beetle, covered with colorful feathers like a rainbow, and its neck is decorated with a little ruby-red ring. The wings appear as if gilded on the underside and the gold-green head wears a tiny cap or hood.

Hummingbirds inspired Hector St. John de Crevecoeur, one of the first American naturalists, to a stirring comparison in his Letters from an American Farmer (1782): “Where do passions find room in so diminutive a body? They often fight with the fury of lions, until one of the combatants falls a sacrifice and dies.”

In addition to providing a fascinating object of study for naturalists and biologists, hummingbirds have piqued the interest of careful observers of all stripes. In his discussion of taste, the eminent German philosopher Immanuel Kant offers hummingbirds as examples of “free natural beauty,” in that they “do not belong to any object determined in respect of its purpose by concepts, but please freely and in themselves.” Despite this enthusiasm, it is likely that Kant — who spent his entire life in Königsberg (now Kaliningrad) — never actually saw a live specimen of the bird. Hummingbirds are not the only instances of free natural beauty that Kant cites: in addition to flowers and sea shells, he also mentions the parrot and the bird of paradise.

Thanks to a certain resemblance to an insect, the hummingbird is known in French as “oiseau mouche” (fly bird). Its fondness for the calyxes of blossoms has inspired the Portuguese names “beija flor” (flower kisser) and “chupa flor” (flower sucker), and the related Spanish “pica flor” (flower poker). In other languages, hummingbirds are known as “Kolibri,” a word likely of Caribbean origin, or Trochilidae, their scientific name (which was provided by Carl Linnaeus and, curiously, seems to relate to a different bird — a type of kinglet called “trochilus” by the ancient Greeks). These inventive names reflect the wonder and enigma that surrounds these creatures and the peculiar abilities and proclivities that set them apart from other birds.

The best-known publication on hummingbirds is John Gould’s massive five-volume study in deluxe folio format, with many illustrations based on stuffed specimens he had commissioned various persons to collect. In addition to authoring A Monograph of the Trochilidae or Humming Birds, Gould organized a contribution to London’s Great Exhibition in 1851 that displayed stuffed specimens representing more than 300 species of these birds. In 1857 — after making a mark with his book and exhibition — Gould traveled to the United States for the first time and finally had the opportunity to observe live specimens and found them to be rather different from his expectations. Its mode of flight “was exactly the opposite of what I had expected,” he remarked.

However, several decades earlier, in the 1830s, the French physician and naturalist René Primevère Lesson (1794-1849), a surgeon, ornithologist, and herpetologist, had already created an impressive work with beautiful illustrations of these birds. He must have been obsessed with these tiny animals in the way other observers of nature develop a passion for butterflies or beetles. Lesson served as the ship’s doctor on the French corvette, Coquille from 1822 to 1825, visiting many South American regions during this time. He then published an extensive monograph on hummingbirds — Histoire naturelle des oiseaux-mouches — with wonderfully detailed lithographs that hold up well against John Gould’s later, more famous works. These beautiful hand-colored copperplate engravings were based on drawings by some of the most celebrated artists of the time.

And it is not particularly surprising that John James Audubon also fell under their spell. For the eminent American ornithological artist, hummingbirds were clad in “glittering garments of the rainbow.” Ernst Haeckel, the biologist who popularized evolutionary theory in Germany, later painted a beautiful color plate illustration with different kinds of hummingbirds that became part of his most famous work, Art Forms in Nature.

Hummingbirds’ attraction to flowers was long attributed somewhat naively to “love.” Blossoms can be seen as advertising by plants to attract the animals that pollinate them; what is more, this botanical advertising is carefully tailored to its target audience. This correspondence explains a great deal, because most birds have a very rudimentary sense of smell; and hummingbirds, as we now know, have no olfactory nerves at all. The situation for bats, in contrast, is completely reversed: as nocturnal animals they respond far more to odors, while colors do little to attract them. For many birds, red is an especially irresistible color, and they tend to prefer bright colors in general. On the whole, the range of colors birds can detect roughly corresponds to the spectrum perceivable by humans. Thanks to this refined sense of sight, hummingbirds can associate the most diverse colors with the nectar from which they draw their sustenance. In Mexico, for example, this could be the crimson snapdragon Penstemon campanulatus in July and the deep blue Salvia mexicana sage in October. Of course, blossoms are the stock in trade of a number of different bird families, but none are as suited for this way of life as the hummingbirds. While other birds can also boast a curved beak with a shape and length to match the blossoms’ form, they need a perch in order to use it. But when a hummingbird finds a choice delicacy, it can partake in the nectar simply by hanging in the air in front of its prize.

Observers are also often surprised by their apparent character. They seem hectic, even downright feverish. In fact, their small size and constant motion make it more difficult for potential predators to catch them. It is astonishingly rare for a hummingbird to fall prey to their natural foes, such as falcons, hawks, starlings, frogs, fish, or even snakes. However, Maria Sibylla Merian mentions the unusual — not to say disturbing — fate of one unlucky hummingbird. After a journey through the Dutch colony of Surinam that began in 1699, Merian described some of the wildlife she had observed in her book, The Insects of Surinam. One of the illustrations shows a pinktoe tarantula with a hummingbird in its jaws.

It used to be a widespread belief in both North America and Argentina that migrating hummingbirds hitch a ride in the feathers of larger birds, such as Canada geese. In addition, people sometimes believed that they had it out for humans, presumably because in moments of curiosity these delicate “attackers” may have come too close to someone’s face. As early as 1847, Philip Henry Gosse, the great English 19th century natural historian, punctured this myth in his book The Birds of Jamaica: “The stories told of Hummingbirds attacking men, and striking at the eyes with their needle-like bills, originated, I have no doubt, in the exaggerating of fear, misinterpreting this innocent curiosity.” It is no surprise that these inscrutable creatures have also inspired a number of poets, including Emily Dickinson, Pablo Neruda, and D.H. Lawrence.

Most early attempts to bring live hummingbirds from America to Europe ended in failure. Even those birds that survived the voyage tended to die shortly after reaching their destination. Faster modes of travel eventually made transporting hummingbirds easier: of 35 hummingbirds from Venezuela packed off for Europe in 1907, 20 arrived alive at the Zoological Society of London. And attempts to keep hummingbirds in captivity posed many challenges. These attempts went hand in hand with efforts to understand exactly what makes up the birds’ diet. In the beginning, people were convinced that hummingbirds live from nectar alone — an idea as romantic as it is false.

Hummingbirds have breathtakingly beautiful plumage, so it’s no wonder that observers have often compared them to diamonds and jewels. But the real secret is not the colors themselves, no matter how intense they may be. Instead, we now know that fine structures of their feathers — tiny horn plates on the surface — partially fragment the light. As a result, their color appears to change depending on how the light strikes them.

Although they share certain external similarities with nectar birds, hummingbirds belong to the order of Apodiformes, which are particularly well adapted to life in the air. If birds in general are the last unfettered creatures, embodying the ancient dream of earthbound humans to rise under their own power, hummingbirds have freed themselves from the bonds of the earth more than any others of their kind. Creatures of the light, they are rarely active after dark. And their highly developed flying capabilities make them acrobats of the air. In fact, flight is the determining principle of their lives. Unlike their relatives, the swifts, they are able to perch on twigs, but their weak legs and undeveloped thigh muscles make them incapable of walking. In a sense, they are the animal counterparts to the Tillandsia — the mobile “air plants” of the Andes whose roots serve only to hold them in place, but which absorb nutrients from the air around them.

Hummingbirds have been slow to give up their secrets. Human observers long puzzled over the mechanism that powers their aerial feats — and this lack of understanding likely fueled our fascination for their buzzing aeronautics. The way a hummingbird flies varies with the occasion. For example, a mating flight can be a dazzling aerial dance. An Anna’s hummingbird may begin a dive toward his mate from 150 feet above the ground, stop midair to sing while peering down at her, and then dive straight toward her at top speed while emitting loud sounds. Their migratory flights are also impressive — some North American species travel several thousand miles on their annual journeys, many of them crossing the Gulf of Mexico.

How can you depict a bird in flight if its movements are so fast that you don‘t understand the mechanics of how it flies? The English naturalist Charles Waterton captured the hummingbird’s peculiar sensual impact in his book Wanderings in South America, the North-West of the United States, and the Antilles in the years 1812, 1816, 1820, & 1824: “See it darting through the air almost as quick as thought! – now it is within a yard of your face! – in an instant gone! – now it flutters from flower to flower to sip the silver dew – it is now a ruby-now a topaz – now an emerald – now all burnished gold.” Alfred E. Brehm, the famous German chronicler of the animal kingdom in the 19th century, wrote that our senses fail us when it comes to hummingbirds: “Even the sharpest eye loses sight of the whirring bird as it flies or is incapable of perceiving it, and the ear can just as little determine the direction and distance of its movements.”

Depicting a hummingbird in flight has always required a certain audacity, since no pencil or brush can really capture its appearance. At least it is clear that the bird’s body hangs vertically in the air and that each buzzing wing forms a half-circle around it: “a semicircular film on both sides,” in the words of Gosse. John Gould wrote that hummingbirds can perform every type of aerial movement with the greatest ease — climbing straight up in the air, flying backwards, spinning on their own axes, or dancing from one spot or part of a tree to another, rising one minute and sinking the next — “that they can fly above the tallest tree and then suddenly shoot down like a meteor.”

In the earliest pictures, the hummingbird’s stationary body is often framed by two semicircles illustrating the perceptible trembling of the air that results when the bird flies in place before a blossom to drink its nectar. But what seems like a simplification is actually quite close to the truth, because a photograph taken with a standard camera shows exactly the same thing.

The evolutionary pressure on hummingbirds to adapt to their unusual circumstances has greatly altered the shape of their wings. Most other birds are capable or flying in one direction only: forwards. To do so, they primarily flap their wings in a vertical rowing motion, with each downward motion providing both propulsion and lift. The act of lifting their wings, in which the wings are partly folded, is a mere counter movement to prepare for the next downward flap. But hummingbird flight is different. Since their wings are so tiny — even though they are not particularly small in relation to their bodies — both movements must contribute to keeping the bird aloft. Its primary feathers are very stiff; a hard, robust quill is a prerequisite for vibrating flight. When flying forward, the birds keep their wings stretched completely straight, turning the tips back slightly only on the upward motion. The decisive difference is only evident during hovering — a hummingbird specialty that demands the greatest changes in flight technique and wing structure.

Towards the end of the 19th century, it became possible to break down the “normal” flight of most birds into its separate components. But capturing the flight of the hummingbird required a stroboscope. MIT professor Harold E. Edgerton, who was interested in making movements visible that could not be perceived with the naked eye, is legendary for his photo of a drop of milk landing to form a “crown.” In 1928, Edgerton began combining a stroboscope and a film camera. He used this device to try to photograph tame hummingbirds that found their way into an acquaintance’s garden to sip from pipettes of syrup he has placed there to attract them. Just a few years later the apparatus was developed to the point that it could take 540 pictures per second. The resulting films showed that hummingbirds beat their wings horizontally, that the upper side of the wings is just as effective at powering flight as the underside, and that the primary feathers do not separate during flight. But the most surprising discovery was that hummingbirds can fly backwards. To accomplish this maneuver, the strongly rotated wings reach back and push the air away, resembling the arms of a swimmer doing the backstroke.

The speed at which hummingbirds move their wings depends on the particular kind of flight they are performing. The ruby-throated hummingbird, for example, manages 55 beats per second when flying in place, 61 when flying backwards, and at least 57 when flying forwards in a straight line. Despite their small size, hummingbirds can achieve considerable speed, but we tend to overestimate their skills in this area. As they shoot through the sky, all the human observer can see is a blur. Still, wind-tunnel measurements have shown that the ruby-throated hummingbird achieves over 26 miles per hour, and a number of tropical species easily reach speeds of almost 44 mph.

No less interesting than the way hummingbirds fly are the unusual sounds that their flight generates — something they have in common with insects. Hummingbirds can often be heard before they are seen. The sounds they make may not be what we expect from such beautiful, delicate creatures. Their calls have been described as chattering, guttural, metallic popping sounds, whistling, or chirping. Some of their sounds have even been compared to a nail scratching a rusty can. In fact, each species of hummingbird produces its own characteristic tone. Gosse demonstrated this fact for the different hummingbird species he studied in Jamaica, which he identified using Lesson’s book. Writing about the Vervain hummingbird, which flocks together “like bees” and causes the air to resound “with their humming, as if in the neighborhood of a hive,” Gosse explained: “Neither of our other species, approaches either the rapidity or extent of this oscillation; and hence with this bird alone does the sound produced by the sound of this vibration acquire the sharpness of an insect’s hum. The noise produced by the hovering of the Polytmus is a whirring exactly like that of a wheel put into rapid revolution by machinery; that of Humilis is a hum, like that of a large bee.” For most birds, the ability to produce their characteristic songs and calls is inborn. However, four of the twenty-three major birds groups — songbirds, parrots, lye birds, and hummingbirds — must learn to make these sounds.

Comparing examples of birds and their environments from around the world enables us to better understand the place hummingbirds occupy in the ecosystem of the Americas, as well as how other animals fill the same function in other areas of the globe. When unrelated species fill the same ecological niche, they are considered to be “ecologically equivalent.” In the avian realm, the nectar birds of Africa and the Australian honey eater — both birds that drink nectar — are the hummingbirds’ ecological equivalents. Viewed in somewhat broader terms, certain bats and insects fit this description as well. The most fascinating comparison involves hawk moths and an especially small type of hummingbird known as the coquette (Lophornis). Not only are they the same size and share the technique of hovering in front of blossoms, but they even sport the same coloration.

Since the bones of hummingbirds are extremely fragile and break down easily, paleontologists long assumed that they would never find any fossils of these birds. But then several amazing discoveries took place, in unexpected places at that. A few years ago, fossilized remains of a hummingbird from the early Tertiary Period were found in Germany, and later in France as well. Gerald Mayr of the Senckenberg Research Institute in Frankfurt gave to his spectacular, over 30-million-year-old find the name Eurotrochilus inexpectatus (unexpected European hummingbird). Although they now exist only in the Americas, hummingbirds were abundant in Europe during the early Oligocene.

Most dangers the hummingbirds themselves face are due to humans. From the 17th century well into the 19th century, these birds were prized for their feathers, especially by European aristocrats. Some ended up in collecting cabinets. In more recent times, the greatest threats have been pesticides and the destruction of natural habitats, because some species only feed on particular flowers and cannot change their preferred diet or environment. Collisions with glass plate windows are also a problem. As a result of factors like these, some species of hummingbirds are now critically endangered.

Today, an entirely new breed of hummingbird has entered the scene. The Nano Hummingbird is a pocket-size, 6.5-inch remote-controlled drone with tiny robotic wings being developed for the Pentagon. This miniature spy-plane has its own energy source and can maneuver intelligently in war zones and urban areas (raising a host of privacy issues). Such drones can be used not only for espionage, but also to investigate hazardous environments.
Capable of reaching speeds of up to 11 miles per hour, it can hover and fly sideways, backwards and forwards, and clockwise and counterclockwise. The current prototype operates for up to eight minutes. In fact, the Nano Hummingbird is smaller and lighter than the largest actual hummingbird. • 17 June 2014

Translated by Lori Lantz