National Geographic Tales of the Weird

by David Braun

  In a new study published in the Public Library of Science journal PLoS ONE, German researchers found that these molecules are linked to an area of the brain known to process visual information. In that sense, “birds may see the magnetic field,” said study lead author Dominik Heyers, a biologist at the University of Oldenburg.

  TRUTH:

  BIRDS CAN SEE TWO TO THREE TIMES BETTER THAN HUMANS.

  Magnetic Orientation

  Man-made compasses work by using Earth as an enormous magnet and orienting a tiny magnet attached to a needle to the planet’s north and south poles. Scientists have thought for years that migratory birds may use an internal compass to navigate between their nesting areas and wintering grounds, which can be separated by thousands of miles. The new research helps explain how this natural compass may work.

  Heyers and his colleagues injected migratory garden warblers with a special dye that can be traced as it travels along nerve fibers. The team put one type of tracer dye into the eyes and another in a region of the brain called Cluster N, which is most active when birds orient themselves. When the birds got their bearings, both tracers traveled to and met in the thalamus, a region in the middle of the brain responsible for vision.

  “That shows there is direct linkage between the eye and Cluster N,” Heyers said. The finding strongly supports the hypothesis that migratory birds use their visual system to navigate using the magnetic field. “The magnetic field or magnetic direction may be perceived as a dark or light spot which lies upon the normal visual field of the bird,” Heyers said, “and which, of course, changes when the bird turns its head.”

  Damaged Magnetic Field Cause of Bird Die-Offs?

  If birds cannot see the magnetic field when migrating, they lose their bearings and could hurt themselves or die. In 2008, NASA reported a “massive breach” of the Earth’s magnetic field. Solar wind can flow into the breach, producing large geomagnetic storms. In addition to this being a possible reason for why thousands of birds across the planet are dying suddenly, it may also cause lost radio transmissions, radiation from too much solar power, and changes in the Earth’s crust, which could lead to increases in landslides, mudslides, earthquakes, and volcanic eruptions.

  More Navigational Tools

  Scientists not involved with the study said it is impressive and well done, but cautioned that there are more pieces to the puzzle of how birds navigate on their long migrations.

  “An animal that has to migrate over great distances needs to have both a compass and a map,” said Cordula Mora, a biologist who recently completed her postdoctoral research at the University of North Carolina, Chapel Hill. Mora’s work suggests that birds may use magnetic crystals in their beaks to sense the intensity of the magnetic field and thus glean information on their physical location.

  “If you have a compass, you know where north, south, east, [and] west [are], but you don’t know where you are, so you don’t know where you should be going,” she said.

  A migratory garden warbler (Photo Credit 6.7)

  Study author Heyers said “both [map and compass] systems may act in concert.”

  Robert Beason is a wildlife research biologist with the U.S. Department of Agriculture in Sandusky Ohio, and an expert on bird navigation. He noted that stars may also either fully or in part provide the birds with their visual bearing—not the magnetic field.

  The next step is to figure out where all this information comes together in the bird brain, he noted. “That’s probably going to tell us where the navigation center for birds is,” he said.

  LONG-DISTANCE RECORD

  Chubby Snipe

  Snaps Nonstop Record

  A plump little shorebird has smashed the record for the fastest long-distance, nonstop flight in the animal kingdom, making a trip from Sweden to sub-Saharan Africa in two days.

  Don’t let the chubby snipe’s name fool you. This is one fast moving bird. In a new study, scientists have discovered that great snipes can complete a transcontinental flight across Europe, from Sweden to sub-Saharan Africa, in as little as two days without resting. The birds traveled up to 4,200 miles (6,760 kilometers) at an average speed of 60 miles (97 kilometers) an hour.

  “If we understand what sleep is doing to their brains then we may be able to manipulate the neurochemistry in the human brain to do something similar someday.”

  Jerome Siegel

  neuroscientist and professor of psychiatry, UCLA, on understanding how birds operate on so little sleep during migrations

  Fast Fat Fliers

  To track the birds, biologists captured and tagged ten great snipes with geolocators at their breeding grounds in western Sweden in May 2009. Tracking data for three of the birds was retrieved after their recapture in Sweden a year later.

  At first glance, great snipes don’t look especially speedy or well equipped for such an arduous journey. Their bodies are small and chubby, not aerodynamic, and in the autumn the birds get so rotund that, when shot, “their skin sometimes ruptures when the shot bird hits the ground,” according to one 19th-century account.

  But it’s these ample fat reserves that allow the birds to fly such long distances without stopping, said study leader Raymond Klaassen, a biologist at Sweden’s Lund University. “They almost double their body weight before the flight,” Klaassen said. “And all this fat will be burned during the flight, and they will arrive lean and exhausted in Africa.”

  All-Nighters

  Birds are known to handle sleep deprivation better than any other mammal. For example, pigeons can survive for months with only about 10 percent of their normal sleep time. One hypothesis for migrating birds’ ability to sleep so little was unihemispheric sleep, where half the brain sleeps and the other half remains active. Dolphins and fur seals are unihemispheric sleepers—they swim and breathe while literally half asleep. However, after preliminary experiments on Swainson’s thrushes, scientists found that unihemispheric sleep was probably not the primary way the birds handled sleep loss. The most intriguing observation was that the thrushes were less active and took more naps during migration season.

  Speed and Endurance

  It’s a rare bird that can fly both far and fast. For example, the Arctic tern racks up as many as 50,000 miles (80,000 kilometers) during its yearly migration from the Arctic to the Antarctic and back again. However, the animal spreads the flight out over several months and fishes along the way. At the other end of the spectrum, peregrine falcons can reach speeds of up to 200 miles (322 kilometers) an hour but only in short bursts to catch prey.

  The only other bird that comes close to matching the great snipe’s abilities is the godwit, a wading bird. In 2007 scientists recorded a godwit flying more than 7,000 miles (11,500 kilometers), from Alaska to New Zealand, in nine days at an average speed of about 35 miles (56 kilometers) an hour. “[One] difference between the godwits and the snipes is that the godwits travel over the ocean, and thus have no possibilities to stop,” Klaassen said. “Hence, their amazing flights are not their choice.”

  By contrast, snipes have several rest-stop options during their autumn migration to Africa but choose not to take advantage of them. The reasons for that are unclear, especially since the birds make several stops during their return flights to Sweden in the spring.

  Bird Migration “Revolution”

  As with other migratory birds that fly long distances, it’s unclear how great snipes can apparently fly for such long periods with little or no sleep. “This is one of the unsolved mysteries of long-distance flights,” Klaassen said. “We now believe that half of their brain sleeps at [a] time, alternating between the left and the right side. Or they do not sleep at all, but this seems impossible regarding the importance of sleep in general.”

  Klaassen says so little is known about bird-migration strategies that he wouldn’t be surprised if the great snipe’s record is broken soon. “Generally we know rather little about the performances of different species, as many have not yet been tracked,�
� he said.

  TRUTH:

  GREAT SNIPES’ SPEED DOES NOT RELY ON WIND ASSISTANCE, WHICH MAKES IT EVEN MORE IMPRESSIVE.

  “I foresee many surprises in the nearby future, due to the recent development of minute tracking devices. The field of bird migration is currently going through a revolution, and these are certainly very exciting times for us.”

  SAY CHEESE!

  Elusive “Smiling” Bird

  Captured on Film

  The notoriously camera shy recurve-billed bushbird put on a happy face for his first photograph in 40 years.

  Call him the Mona Lisa of the bird kingdom. The rare recurve-billed bushbird, recently rediscovered by scientists in Colombia after a 40-year absence, sports a curving beak that gives the illusion of an enigmatic smile.

  Say cheese! The rare recurve-billed bushbird poses for the camera. (Photo Credit 6.8)

  Ready for His Close-Up

  The photograph, taken by a conservationist with the Colombia-based nonprofit Fundación ProAves in 2005, is the first photo released of a live bushbird. The elusive species had not been spotted between 1965 and 2004, due to its limited range and remote habitats. It was seen recently in Venezuela and in a region of northeastern Colombia, where it was photographed.

  Researchers found the bird in a 250-acre (101-hectare) reserve next to the Torcoroma Holy Sanctuary near the Colombian town of Ocaña, where in 1709 locals claimed they saw the image of the Virgin Mary in a tree root. The forests of the sanctuary have been protected by Catholic Church authorities in the centuries since.

  TRUTH:

  THE BUSHBIRD USES ITS UNIQUE BILL TO SLICE OPEN THIN BAMBOO SHOOTS AND DIG OUT BEETLE LARVAE AND OTHER ARTHROPODS FROM THE STALK.

  Another Rare Bird

  The researchers also found and photographed the extremely rare Perija parakeet, of which only 30 to 50 individuals likely survive. Deforestation and wildfires for agriculture and grazing have denuded much of the birds’ habitat, conservationists say.

  “[A]s more and more remote areas are being settled, the bushbird reminds us how important it is to conserve as much natural habitat as we can,” said Paul Salaman of the American Bird Conservancy. “Who knows what wonderful biodiversity is being destroyed before it has had a chance to be discovered?”

  MIGHTY FAST MUSCLES

  Superfast Muscle Power

  Found in Songbirds’ Throats

  Faster than a speeding … songbird? The world’s fastest moving muscles don’t belong to Olympic sprinters, they’re in the throats of songbirds.

  The fastest muscles known lie within the throats of songbirds, according to new research on how birds vibrate their vocal cords. The study, published in the journal PLoS One, shows that the muscles used by birds to create their songs are the speediest of all.

  TRUTH:

  THE ZEBRA FINCH WAS THE SECOND BIRD TO HAVE ITS GENOME SEQUENCED AFTER THE CHICKEN.

  Strong Songs

  Experts have long wondered whether bird song is caused by passive interactions as air moves between the vocal muscles or direct neuromuscular control.

  “I had been looking at the muscles in a pigeon species and was amazed by how fast they were moving,” said lead study author Coen Elemans at the University of Utah in Salt Lake City. “[Pigeons] have really boring, slow songs, and it made me wonder what the muscles in songbirds were like, so I decided to find out.”

  What Elemans and colleagues discovered is that zebra finches and European starlings can change their tunes at frequencies as high as 250 hertz via direct muscle control. This means that they are moving their muscles a hundred times faster than a blink of the human eye.

  “Superfast muscles were previously known only from the sound-producing organs of rattlesnakes, several fish and the ring-dove. We now have shown that songbirds also evolved this extreme performance muscle type, suggesting these muscles—once thought extraordinary—are more common than previously believed.”

  Coen Elemans

  biology researcher, University of Southern Denmark

  Extremely Fast Twitch

  To find out how songbirds make their quick-fire modulations, the researchers first measured muscle activity in freely singing starlings and found that muscle motion corresponded to changes in song tone.

  The team then exposed vocal muscle fibers from starlings and zebra finches to electrical stimulation in the lab to see just how fast the muscles can expand and contract. The vocal muscles of male and female starlings both contracted at about 3.2 milliseconds. Male zebra finch muscles, meanwhile, twitched at roughly 3.7 milliseconds while females’ moved at 7.1.

  Tiny twitching muscles on either side of rattlesnake rattles, along with muscles in the swim bladders of some fish, have been recorded approaching these speeds. But Elemans’s team concludes that songbird vocal cords move faster than any muscle in any other known vertebrate.

  Since most songbirds have the same general type of vocal cords, the discovery could mean that extremely fast-moving muscles are more common in nature than was previously thought.

  Synchronized Chorus

  Daniel Margoliash, a biologist at the University of Chicago who was not involved with the study, called the paper “as elegant as it is exciting.” “We’ve been fascinated by bird songs for so long, and this gives us a very important insight into the vocal organs behind them,” he said. “We had no idea muscles could work at these superfast rates,” he added. “That they can and do is just amazing.”

  Daniel Mennill, an avian biologist at the University of Windsor in Canada, noted that fieldwork has shown songbird vocalizations to be among the most precisely timed behaviors in the animal kingdom. “The synchronized duets and choruses of wrens, for example, are the most highly coordinated animal behaviors ever recorded,” he said. “These [new] results explain a lot about how birds actually achieve such amazing technical feats.”

  TRUTH:

  MALE NORTHERN MOCKINGBIRDS MAY LEARN AS MANY AS 200 SONGS THROUGHOUT THEIR LIVES.

  Study leader Elemans said he is keen to continue his search for creatures with superfast muscles, and he thinks bats will be good candidates. “Bats echolocate with an auditory sweep that rapidly moves from very high pitch to very low,” he said. “I’m convinced that there are fast-moving muscles behind this sonic sweep.”

  SMART BIRDS

  Crows Have Human-Like Intelligence

  Author Says

  Clever crows are one of nature’s brainiest birds, sharing the similar hallmarks of higher intelligence with humans.

  Crows make tools, play tricks on each other, and caw among kin in a dialect all their own. These are just some of the signs that point to an unexpected similarity between the wise birds and humans. “It’s the same kind of consonance we find between bats that can fly and birds that can fly and insects that can fly,” said Candace Savage, a nature writer based in Saskatoon, Canada.

  “Species don’t have to be related for there to have been some purpose, some reason, some evolutionary advantage for acquiring shared characteristics,” she added.

  Crows are one of the few species that use tools. (Photo Credit 6.9)

  Brainy Black Birds

  Author of Crows: Encounters with the Wise Guys of the Avian World, Savage explores the burgeoning field of crow research, which suggests that the birds share with humans several hallmarks of higher intelligence, including tool use and sophisticated social behavior.

  Sharing Intel

  In a five-year study of crows living near Seattle, researchers discovered that the crows can remember a “dangerous human” and are able to share their knowledge of the danger with their offspring and other crows. “Because human actions often threaten animals, learning socially about individual people’s habits would be advantageous,” says study co-author John Marzluff of the University of Washington. “Crows recruit and tolerate others of their own and different species in mobs that form around dangerous people. This social tolerance could allow naïve crows to learn about dangerous situat
ions, locations and individual humans.”

  The shared traits exist despite the fact that crows and humans sit on distinct branches of the genetic tree. Humans are mammals and crows are birds, which Savage calls feathered lizards, referring to the theory that birds evolved from dinosaurs.

  “I’m not positing there’s anything mythological about this or imagining crows are in any way human,” she said. “But whatever it is that has encouraged humans to develop higher intelligence also seems to have been at work on crows.”

  Tool Use

  Alex Kacelnik is a zoologist at Oxford University in England who studies tool use in crows. He said study of the birds advances understanding of how higher intelligence evolves.

  As a sign of crows’ advanced smarts, Savage cites Kacelnik’s 2002 study in the journal Science on a captive New Caledonian crow that bent a straight piece of wire into a hook to fetch a bucket of food in a tube. “No other animal—not even a chimp—has ever spontaneously solved a problem like this, a fact that puts crows in a class with us as toolmakers,” Savage writes in her book.

  Kacelnik noted that New Caledonian crows, which are restricted to a few islands in the South Pacific Ocean, are the only example of some 45 crow species that “are very intense tool users in nature.” ’ Nevertheless, he continued, these birds are “both intense tool users and creative tool users … In addition to the tools they are normally seen to use in the wild, they are capable of making new instruments when the necessity arises,” such as the wire hooks.