Discovering owls

SPECIES WATCH Through the Global Owl Project, researchers across 65 countries are compiling a vast database of all the world’s owls, with descriptions, natural history, genetics, vocalisations and rough population estimates. For all its familiarity, scientists are only now beginning to understand the owl, writes Natalie Angier

The day after a frigid, star-salted night spent tromping through the Alexandria, Va., woods with David Johnson of the Global Owl Project, and listening to the stridently mournful cries of wild barred owls that remained hidden from view, I stopped by the National Zoo around sunset to take visual measure of the birds I had heard.

The two barred, or Strix varia, owls were just rousing themselves in the outdoor enclosure, and they looked bigger and more shaggily majestic than I expected, with capes of densely layered cream-and-coffee plumage draped on their 17-inch frames and pompous, Elizabethan feather ruffs encircling their necks. Like any good royalty, they ignored me. That is, until I pulled out my phone with the birdcall app and started playing the barred owl song. The female’s languid eyes shot wide open. The male’s head spun around in its socket by 180 of the 270 degrees an owl’s head can swivel.
With the distinctive forward-facing gaze that can make owls seem as much human as bird, the barred pair stared at me. I played the call again, the male grew bored, and I was about to put the phone away when suddenly the female — the larger of the two owls, as female birds of prey often are — pitched her body forward on her perch, lifted up her heavy, magnificent wings and belted out a full-throated retort to my recorded call.

In the Western imagination, the owl surely vies with the penguin for the position of ‘My Favorite Bird’. “Everyone loves owls,” said David J. Bohaska, a paleobiologist at the Smithsonian’s National Museum of Natural History, who discovered one of the earliest owl fossils. Owls are a staple of children’s books and cultural kitsch – here wooing pussycats in pea-green boats and delivering mail to the Harry Potter crew. Yet for all this apparent familiarity, only lately have scientists begun to understand the birds in any detail, and to puzzle out the subtleties of behaviour, biology and sensory prowess that set them apart from all other avian tribes.

Researchers have discovered, for example, that young barn owls can be impressively generous toward one another, regularly donating portions of their food to smaller, hungrier siblings – a display of altruism that is thought to be rare among nonhuman animals, and one that many a small human sibling might envy. The scientists also discovered that barn owls express their needs and desires to each other through a complex, rule-based series of calls, trills, barks and hoots, a language the researchers are now seeking to decipher. “They talk all night long and make a huge noise,” said Alexandre Roulin of the University of Lausanne, who recently reported on barn owl altruism in the journal Animal Behaviour with his colleague Charlene A Ruppli, and Arnaud Da Silva of the University of Burgundy. Other researchers are tracking the lives of some of the rarer and more outlandishly proportioned owls, like the endangered Blakiston’s fish owl of Eurasia.

Nearly a yard high, weighing up to 10 pounds and with a wingspan of 6 feet, Blakiston’s is the world’s largest owl, a bird so hulking it’s often mistaken for other things, according to Jonathan Slaght of the Wildlife Conservation Society’s Russia programme. This powerful predator can pull from the river an adult salmon two, three or more times its own weight, sometimes grabbing onto a tree root with one talon to help make the haul.

Ferocity’s crucial

Ferocity is essential for a bird whose frigid, spotty range extends across northeastern China, the Russian Far East and up toward the Arctic Circle, one that breeds and nests in the dead of winter, perched atop a giant cottonwood or elm tree, out in the open, in temperatures of 30 degrees below zero Fahrenheit. Slaght’s colleague Sergei Surmach videotaped a female sitting on her nest during a blizzard. Aeronautical engineers are studying owls for clues to better wing designs. Many owl species are renowned for their ability to fly almost silently, without the flapping noises and air whooshes that might warn prey of their approach.

Researchers have traced that silent flight to several features. The bulk of the wing is broad and curved — the ideal shape for slow gliding — and is abundantly veined with velvety down plumage to help absorb sound. Moreover, the feathers at the edge of the wing are serrated to effectively break up and smooth out air turbulence as a comb disentangles knots. At a meeting of the American Physical Society last fall, researchers from Cambridge University proposed that well-placed perforations in an airplane wing could have a similar smoothing effect on turbulence, leading to quieter and more efficient flights – and mealtime voles for all.

Owls date back 60 million years or longer, and they’re found in nearly every type of habitat: tropical, tundra, desert, Central Park. Some 229 species are known, and the list keeps growing: Last summer, two new species of hawk owl were discovered in the Philippines, and this month researchers reported on a new species of screech-like owl from the island of Lombok, Indonesia. The birds own the night, although some hunt at dusk and dawn and even during the day. And hunt owls tirelessly do. By one estimate, a group, or “parliament,” of 10 owl families living in a barn in Central Florida cleared the surrounding sugarcane fields of about 25,000 cotton rats a year. Owls were long thought to be closely related to birds of prey like hawks and eagles, which they sometimes superficially resemble — hence the names hawk owls and eagle owls. But similarities of beak or talon turn out to be the result of evolutionary convergence on optimal meat-eating equipment, and recent genetic analysis links the owls to other nocturnal birds, like nightjars.

Database of owls

Through the Global Owl Project, Johnson is working with researchers in 65 countries to compile a vast database and celebration of all the world’s owls, with descriptions, natural history, genetics, vocalisations, rough population estimates, owl myths and legends.

Species like the barn, barred, screech and horned have some of the keenest auditory systems known, able to hear potential prey stirring deep under leaves, snow or grass, identify the rodent species and even assess its relative plumpness or state of pregnancy, based on sound alone.Again scientists attribute that to a consortium of traits. Tim Birkhead of the University of Sheffield points out in his new book, “Bird Sense,” that the owl cochlea is “enormous” and densely packed with sensory cilia. The barn owl has three times the number of hair cells expected for its body size. The paired ear openings are also exceptionally large and asymmetrically placed on either side of the skull, the better to help localise a sound’s origin; the super-swively neck further enhances the power to sample the ambient soundscape.

Then there is the owl’s famously flat face, also called the facial disk – pie-shaped in some species, heart-shaped Kabuki in the barn owl. The facial disk serves as a kind of satellite dish, to gather sound waves, which are then directed to the owl’s ears by stiff, specialised feathers.