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iStock

Hummingbirds Can Withstand Turbulence Remarkably Well

iStock
iStock

You've probably seen a slow-motion video of a hummingbird suspended in the air, wings flapping furiously to keep himself stationary as he enjoys a mid-flight sugary treat. But what about when there's wind? Hummingbirds can't go hungry just because there's a little weather to contend with. Sridhar Ravi, the lead scientists on a new study out about hummingbird stability in the face of turbulence, explained to Popular Mechanics that hummingbirds have to deal with different wind conditions all the time.

"That's like asking, 'how often do walking animals encounter uneven terrain?'" he said. "The answer is, basically all the time and they need to come up with strategies to contend with the unsteadiness of the medium."

To test how well hummingbirds deal with this unsteadiness, Ravi and his team tracked the body movements of four female ruby-throated hummingbirds as they navigated a wind tunnel to reach a sugar feeder at the far end. What they found was that hummingbirds are unparalleled at staying steady: Faced with winds of up to 10 mph, the hummingbirds kept their heads perfectly still while the rest of their bodies careened around to compensate. For comparison's sake, the 10 mph winds were considered a "turbulence intensity" of 15 percent. When professional pilots attempted the feat with mini drones, none of them could even keep the crafts in the air at a turbulence intensity of 5 percent.

Still too obscure? Ravi compared this feat to "asking a person to maintain perfect handwriting in a car as it is being driven off-road. Also note that the birds are experiencing accelerations up to 1G, implying the person must perform the task in the off-road car while instantaneously experiencing forces equivalent to their own weight!"

What the scientists didn't learn from this study is how the hummingbirds stay so steady. And while that research is certainly upcoming, don't hold your breath for hummingbird-style planes—Ravi said that their wings are just too complicated for us to mimic.

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Christie's
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Art
A Rare Copy of Audubon's Birds of America Could Break Records at Auction
Christie's
Christie's

American artist and naturalist John James Audubon published The Birds of America in the first half of the 19th century, and his massive “double-elephant” folio of life-size bird illustrations remains one of the most ambitious nature books ever produced. On June 14, a rare edition of the four-book set is hitting the auction block, and it's expected to fetch up to $12 million—more than any Audubon book ever sold.

This edition of The Birds of America was owned by the dukes of Portland from around 1839 to 2012. Because it was stored on the shelves of the family's Nottinghamshire, England estate for nearly a century, the set's prints of watercolor drawings have remained remarkably well-preserved.

In 2012, the copy was auctioned off to philanthropist and businessman Carl W. Knobloch, Jr. for nearly $8 million. Knobloch donated the books to the Knobloch Family Foundation (KFF) before his death in 2016. Now, the KFF is sending the books to auction once again. This time, all proceeds of the sale will go to nature conservation.

Set of red leather-bound books.

New York City auction house Christie's describes the set in a listing as "among the finest copies in private hands of this icon of American art, and the finest color-plate book ever produced." Each of the 435 double-elephant folio pages measures 39.5 inches by 26.5 inches, the largest sheets Audubon could get his hands on at the time, and they feature 1037 birds from 500 species. The books are bound in red Moroccan leather with gold detailing on the borders and spines. The four-volume set also comes with the Ornithological Biography, a collection of five books describing the specimens in The Birds of America and their habits.

Christie's estimates the set will sell for $8 million to $12 million when the final bid is placed later this month. To date, the most expensive copy of The Birds of America was a first edition acquired from Sotheby's in London for $11.5 million. That sale also broke the record for the most expensive printed book ever sold at auction, a record held until 2013.

Illustration of American birds.

Illustration of American bird.

Illustration of American birds.

Illustration of American birds.

Illustration of American birds.

All images courtesy of Christie's

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Jana Mueller
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Animals
Ravens Can Figure Out When Someone Is Spying on Them
Jana Mueller
Jana Mueller

Corvids, the family of birds that includes crows and ravens, are canny beasts. They've been known to exercise self-control, count, hold grudges, and more. Now, new research suggests they possess at least a rudimentary Theory of Mind—the ability to attribute mental states to others.

A study in Nature finds that ravens can tell when someone else can see them, guarding their food when a peephole to their cache is open. While previous research suggested that birds might have an awareness of other animals' mental states, the results have been inconclusive. The Nature study is evidence that corvids can do more than just track other birds' gaze; they may understand the concept of "seeing."

Vienna-based researchers set up two rooms separated by windows that could be closed with covers. These covers had peepholes in them that could also be opened or closed. First, the 10 ravens were each allowed to cache food, while other birds were in the next room and the windows were open or closed. Then, they were trained to look through the peepholes to find food in the other room, so that they knew that the holes could be used to see through the window covers. Afterwards, each of the ravens was again presented with food with one of the two peepholes open. The adjacent observation room didn't have any birds in it, but the researchers played the sounds of another raven recorded during one of the previous trials.

When the birds heard the sounds of another raven in the next room, and the peephole was open, the birds behaved as if they knew they were being watched—they hid their cache of food quickly and didn't add more food to it as often, as if they knew that it might be compromised. However, they behaved normally when the peephole was closed.

This suggests that ravens don't just track their competitors' gaze to know when they’re being watched, but can infer from past experience when they can be seen.

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