July 10, 2021 | David F. Coppedge

Life Exceeds Expectations: Birds

Here are some marvelous birds with abilities
above and beyond the call of survival duty

 

During epic migrations, great snipes fly at surprising heights by day and lower by night (Science Daily). This is not a snipe hunt joke. Great snipes are real birds, and these ones fly high. Scientists at Lund University in Sweden were astonished to log them flying as high as some airliners. They normally fly at the “surprising” altitude of 8,200 feet during the day, and lower their altitude at night, for unknown reasons. And their flights are non-stop:

Don’t let the great snipe’s pudginess fool you. A stocky marsh bird with a 20-inch wingspan, great snipes are also speedy marathoners that can migrate from Sweden to Central Africa in just three days, without even stopping to eat, drink, or sleep. Now, researchers find that the snipes also rise nearly 2,500 meters in elevation at dawn and descend again at dusk each day, perhaps to avoid overheating from daytime solar radiation by climbing to higher, cooler altitudes. The findings appear June 30 in the journal Current Biology.

Installing miniature data loggers on their feet, the scientists were able to record activity, air pressure, and temperature every hour. One bird was found to reach 8,700 meters – over 28,000 feet! This is “possibly the highest altitude ever recorded for an identified migrating bird,” they said. Why do they do it? “The reasons behind these altitude changes are not well understood.” Maybe they just like to show off.

Lindström et al., 2021, Extreme altitude changes between night and day during marathon flights of great snipes. Current Biology June 30, 2021 (open access). DOI:10.1016/j.cub.2021.05.047.

We may finally know how migrating birds sense Earth’s magnetic field (New Scientist). There’s little doubt that birds are able to use the Earth’s magnetic field to navigate, but how they do it has remained mysterious. One theory is that the birds can sense bits of magnetic material, like magnetite, moving in some cells. A competing theory would make birds as smart as physicists in quantum mechanics. Certain proteins called cryptochromes might have the ability to create “quantum pairs” that are sensitive to magnetic fields. A press release from the University of Oldenburg explains what was discovered about “quantum birds” —

Model of protein interactions from the Nature Video.

Humans perceive the world around them with five senses – vision, hearing, taste, smell and touch. Many other animals are also able to sense the Earth’s magnetic field. For some time, a collaboration of biologists, chemists and physicists centred at the Universities of Oldenburg (Germany) and Oxford (UK) have been gathering evidence suggesting that the magnetic sense of migratory birds such as European robins is based on a specific light-sensitive protein in the eye. In the current edition of the journal Nature, this team demonstrate that the protein cryptochrome 4, found in birds’ retinas, is sensitive to magnetic fields and could well be the long-sought magnetic sensor.

If this protein in the bird’s eyes reacts to the magnetic field, it might create a “shading” effect in its vision, a team member explains. The amount of shading could help the bird orient correctly. “But the group hasn’t yet demonstrated that cryptochrome 4 is being used for magnetic sensing in real life,” Clare Wilson writes in New Scientist, and so the theory remains unproved. Nature produced a video clip about the theory, “How quantum physics guides birds,” featuring some of the German team members who identified CRY4 as the possible magnetic sensor made of protein.

Here are additional references about this developing story:

  • Paper: Jingjang Xu et al., 2021. Magnetic sensitivity of cryptochrome 4 from a migratory songbird. Nature 594, pages 535–540 (2021), published June 23.
  • Unravelling the enigma of bird magnetoreception (Nature News and Views), June 23, 2021.
  • Clues to how birds migrate using Earth’s magnetic field (Helen Briggs, BBC News), June 23, 2021.

Credit: Illustra Media.

To appreciate just how precise and sensitive the bird magnetic navigation is, consider what the Air Force is trying to do. Next month, the US Air Force will test a new navigation device that monitors tiny changes in Earth’s magnetic field, David Hambling reports in New Scientist. Why use artificial GPS when the Earth already has a coordinate system? It works over the ocean, where other navigation aids like landmarks and radio beams are not available to pilots. It’s also difficult to jam or spoof, Hambling notes. Engineering challenges include making the magnetic sensor compact enough, and shielding it from other magnetic sources inside the plane. Birds have those matters already figured out.

Eagle-inspired robot flies by flapping its feather-covered wings (New Scientist); Raptor-inspired drone with morphing wing and tail (EPFL). Here are two reports of teams trying to fly like an eagle. In the first one from 3 March 2021, Matthew Sparkes shows a video of a Chinese model inspired by a golden eagle. The second story shows a feather-covered drone inspired by a goshawk. It can move its wings and its tail.

“Goshawks move their wings and tails in tandem to carry out the desired motion, whether it is rapid changes of direction when hunting in forests, fast flight when chasing prey in the open terrain, or when efficiently gliding to save energy,” says Enrico Ajanic, the first author and PhD student in Floreano’s lab. And Floreano adds “Our design extracts principles of avian agile flight to create a drone that can approximate the flight performance of raptors, but also tests the biological hypothesis that a morphing tail plays an important role in achieving faster turns, decelerations, and even slow flight”.

It’s great to see modern teams taking inspiration from the birds, like the Wright Brothers did. If they ever get one to lay eggs that hatch drone chicks, they’ll really be onto something.

 

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Categories: Amazing Facts, Biology, Birds

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