It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Thursday, March 11, 2021
Whooping cranes steer clear of wind turbines when selecting stopover sites
Proliferation of wind-energy infrastructure across the Great Plains has created obstacles along key migration routes; future developers could place infrastructure outside of migration corridors to avert negative impacts
THEY SUMMER IN LETHBRIDGE. ALBERTA WHICH IS ALSO HOME TO WIND TURBINES
IMAGE: A PAIR OF WHOOPING CRANES WALKING ALONG THE EDGE OF A WETLAND IN CENTRAL KANSAS view more
CREDIT: TRAVIS WOOTEN/USGS
As gatherings to observe whooping cranes join the ranks of online-only events this year, a new study offers insight into how the endangered bird is faring on a landscape increasingly dotted with wind turbines. The paper, published this week in Ecological Applications, reports that whooping cranes migrating through the U.S. Great Plains avoid "rest stop" sites that are within 5 km of wind-energy infrastructure.
Avoidance of wind turbines can decrease collision mortality for birds, but can also make it more difficult and time-consuming for migrating flocks to find safe and suitable rest and refueling locations. The study's insights into migratory behavior could improve future siting decisions as wind energy infrastructure continues to expand.
"In the past, federal agencies had thought of impacts related to wind energy primarily associated with collision risks," said Aaron Pearse, the paper's first author and a research wildlife biologist for the U.S. Geological Survey's Northern Prairie Wildlife Research Center in Jamestown, N.D. "I think this research changes that paradigm to a greater focus on potential impacts to important migration habitats."
The study tracked whooping cranes migrating across the Great Plains, a region that encompasses a mosaic of croplands, grasslands and wetlands. The region has seen a rapid proliferation of wind energy infrastructure in recent years: in 2010, there were 2,215 wind towers within the whooping crane migration corridor that the study focused on; by 2016, when the study ended, there were 7,622 wind towers within the same area.
Pearse and his colleagues found that whooping cranes migrating across the study area in 2010 and 2016 were 20 times more likely to select "rest stop" locations at least 5 km away from wind turbines than those closer to turbines.
The authors estimated that 5% of high-quality stopover habitat in the study area was affected by presence of wind towers. Siting wind infrastructure outside of whooping cranes' migration corridor would reduce the risk of further habitat loss not only for whooping cranes, but also for millions of other birds that use the same land for breeding, migration, and wintering habitat.
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The Ecological Society of America, founded in 1915, is the world's largest community of professional ecologists and a trusted source of ecological knowledge, committed to advancing the understanding of life on Earth. The 9,000 member Society publishes five journals and a membership bulletin and broadly shares ecological information through policy, media outreach, and education initiatives. The Society's Annual Meeting attracts 4,000 attendees and features the most recent advances in ecological science. Visit the ESA website at https://www.esa.org.
CAPTION
A whooping crane (Grus americana) family in their wintering grounds at Aransas National Wildlife Refuge in Texas.
CREDIT
Klaus Nigge/USFWS
Birds learn to avoid flashy, hard-to-catch butterflies and their lookalikes
IMAGE: RESEARCH SUGGESTS SHOWY COLORS AND PATTERNS IN CERTAIN BUTTERFLIES COULD WARN PREDATORS OF THEIR SPEED AND AGILITY. IN ADELPHA BUTTERFLIES, MANY DISTANTLY RELATED SPECIES HAVE ONE OF THREE COMMON "RACING... view more
CREDIT: JEFF GAGE/FLORIDA MUSEUM OF NATURAL HISTORY
GAINESVILLE, Fla. --- The showy colors of some butterflies could advertise their speed and nimbleness, much like a coat of bright yellow paint on a sports car. A new study shows birds can learn to recognize these visual cues, avoiding not only butterflies they've failed to nab in the past but similar-looking species as well.
The research provides some of the strongest evidence to date for the idea of evasive mimicry, a strategy in which animals protect themselves from predators by matching the colors or patterns of agile relatives. First proposed more than 60 years ago, the hypothesis has been a challenge to test.
But in an experimental setting, researchers found that wild birds learned and remembered the wing patterns of artificial butterflies that evaded their attacks, as well as those that had a foul flavor, equally spurning both in follow-up tests and often ignoring lookalikes with similar color patterns. Unexpectedly, the birds learned to avoid evasive butterflies faster than distasteful ones.
The results suggest that being hard to catch may deter predators at least as effectively as chemical defenses.
"There's a common idea that being distasteful is one of the best kinds of defense to have, but at least in this experiment, that didn't prove to be the case," said study co-author Keith Willmott, curator and director of the Florida Museum of Natural History's McGuire Center for Lepidoptera and Biodiversity.
Most research on warning coloration has focused on species with chemical defenses and those that mimic them. Monarch butterflies, for example, sport bright wing patterns of black lines on a field of orange, indicating they contain bad-tasting toxins. A predator that eats one will likely avoid both monarchs and the similar-looking viceroy butterfly in the future.
But a growing number of studies suggest a flashy exterior can mean something entirely different: that an animal is quick. Predators learn to associate these kinds of patterns with a futile chase that leaves them hungry, and species that evolve imitations of these "racing stripes" can capitalize on a defensive strategy while reinforcing the visual message.
"When many species share the same color pattern, they're better able to educate predators to avoid them," Willmott said. "The more species that share it, the better."
During his Ph.D. studies, Willmott worked on the classification of a group of fast-flying tropical butterflies known as Adelpha. At first, he found them nearly impossible to identify. It seemed the genus either contained only a few species with slight variations in wing pattern or dozens of species that looked virtually the same. The latter turned out to be the case, with more than 90 species making up the group. Like some researchers before him, Willmott began to wonder whether evasive mimicry could explain why so many species of Adelpha looked alike.
"It was always mysterious to me," he said. "Species whose upper wings looked incredibly similar were distantly related, and we started to see cases where even subspecies of multiple species suddenly developed very unique color patterns. Really, the only way you can explain that is through mimicry."
While other researchers suggested some Adelpha must have hidden chemical defenses, the explanation didn't quite satisfy Willmott. Toxic butterflies are usually slow fliers with long wings and a propensity for playing dead when caught. Adelpha butterflies, however, don't display these traits, having instead a short, stout thorax and smaller, triangular wings - characteristics that enable fast, erratic flight and sharp turns.
But he wasn't sure how to test this hypothesis until a conversation with fellow researchers at a 2018 conference in India: Johanna Mappes was an expert at developing predator-prey experiments with wild birds; Pável Matos-Maraví was interested in the evasive behavior of skipper butterflies; and Marianne Elias and her Ph.D. student Erika Páez were eager to study what drove the evolution of wing color patterns in the genus Adelpha, including the possible effects of predators.
Simulating how evasive mimicry might play out in the wild appealed to the group. The ability of prey to escape predators' attacks has been "virtually unstudied," said Elias, a research group leader at the Institute of Systematics, Evolution, Biodiversity at the National Museum of Natural History in France.
CAPTION
Because many species in the genus Adelpha look alike from the top, researchers often use their intricately patterned undersides to distinguish them. From left, these butterflies are Adelpha salmoneus, Adelpha cocala and Adelpha epione.
CREDIT
Jeff Gage/Florida Museum of Natural History
Previous work had shown birds can identify the visual cues of evasive prey. Together, the team designed an experiment to test whether potential examples of evasive mimicry in Adelpha could be the result of natural selection.
At a special facility in Finland, the researchers collaborated with Janne Valkonen of the University of Jyväskylä to capture wild blue tits, birds that would never have encountered tropical Adelpha butterflies, and train them to catch a paper butterfly with an almond treat attached to its underside. Then, the birds were presented with a plain brown paper butterfly as a control and a paper butterfly with one of three common Adelpha wing patterns: a vertical white band on black forewings, a vertical orange band on black forewings or a combination of orange-striped forewings with white-striped hindwings.
The paper Adelpha butterfly either concealed an almond soaked in a bitter substance - a proxy for chemical defense - or evaded the bird's attack by gliding away on a rail. The birds learned to connect a particular wing pattern with the negative experience of distastefulness or escape, eventually avoiding this butterfly and striking the control instead. In a final test, they were given four butterflies at the same time: the plain brown butterfly and all three Adelpha butterflies, including one with the pattern they had seen before.
They strongly avoided the butterfly they had learned to associate with the bitter almond or fast flight and often avoided butterflies that shared a similar color or pattern.
Birds were 1.6 times more likely to attack the distasteful butterfly than evasive ones, perhaps because they had varying levels of tolerance for the bad-tasting almond, said Páez, who co-led the study with Valkonen. After all, even a bitter morsel of food is better than nothing.
"Bad-tasting prey could provide a nutritive meal whereas missing prey completely cannot," she said.
While birds tend to avoid colorful prey by default, the study provides evidence of learned behavior, Willmott said.
"This potentially explains many cases of apparent mimicry that lacked evidence of chemical defense."
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Matos-Maraví of the Biology Centre, Czech Academy of Sciences, and Mappes of the University of Jyväskylä and the University of Helsinki also co-authored the study.
CAPTION
Researchers trained wild birds to attack paper butterflies with an almond treat attached to the underside, bottom left. They then gave birds a plain brown butterfly, center, and a striped butterfly that was either hard to catch or concealed a bitter almond. Birds eventually avoided the evasive and distasteful prey.
CREDIT
Erika Páez
CLOAKING DEVICE
Optimal design for acoustic unobservability in water
VIDEO: SQUARE NORM OF SOUND PRESSURE IN WATER AROUND A DESIGNED ACOUSTIC CLOAK DURING TOPOLOGY OPTIMIZATION. view more
CREDIT: GARUDA FUJII, INSTITUTE OF ENGINEERING, SHINSHU UNIVERSITY, JAPAN
Until now, it was only possible to optimize an acoustic cloaking structure for the air-environment. However, with this latest research, Acoustic cloak designed by topology optimization for acoustic-elastic coupled systems, published in the latest Applied Physics Letters, it is possible to design an acoustic cloak for underwater environments.
In the conventional topology optimization of acoustic cloaking, the design method was based on an analysis that approximated an elastic body in the air as a rigid body. However, since the approximation holds only for materials that are sufficiently stiff and dense such as metal in the air, there were few material options other than metal. Moreover, it was impossible to design an acoustic cloak in water by the approximation method.
In this study led by Garuda Fujii of Shinshu University, the group developed topology optimization based on the finite element analysis of coupled acoustic-elastic wave propagation. By considering the interaction between the vibration of the elastic body and the sound wave in the optimization calculation, it is now possible to select the material that constitutes the acoustic cloak from light ABS and other materials and to design the acoustic cloak for use in air and water. Furthermore, the group successfully designed wide frequency band acoustic cloaks optimized respectively for each environment, aerial and underwater.
This novel research has made it possible to select the constituent materials of the acoustic cloak and the surrounding acoustic medium environment (air or underwater) with a high degree of functionality. It is expected that the functions of acoustic cloaking will be greatly expanded.
IMAGE: ENGINEERS CONDUCTED EXPERIMENTS WITH "DUMB " HEADPHONES WITH ESTIMATED PRICES RANGING FROM $2.99 TO $15,000. HEADFI CAN TRANSFORM SUCH HEADPHONES INTO SMART ONES. view more
CREDIT: XIAORAN FAN
How do you turn "dumb" headphones into smart ones? Rutgers engineers have invented a cheap and easy way by transforming headphones into sensors that can be plugged into smartphones, identify their users, monitor their heart rates and perform other services.
Their invention, called HeadFi, is based on a small plug-in headphone adapter that turns a regular headphone into a sensing device. Unlike smart headphones, regular headphones lack sensors. HeadFi would allow users to avoid having to buy a new pair of smart headphones with embedded sensors to enjoy sensing features.
"HeadFi could turn hundreds of millions of existing, regular headphones worldwide into intelligent ones with a simple upgrade," said Xiaoran Fan, a HeadFi primary inventor. He is a recent Rutgers doctoral graduate who completed the research during his final year at the university and now works at Samsung Artificial Intelligence Center.
A peer-reviewed Rutgers-led paper on the invention, which results in "earable intelligence," will be formally published in October at MobiCom 2021, the top international conference on mobile computing and mobile and wireless networking.
Headphones are among the most popular wearable devices worldwide and they continue to become more intelligent as new functions appear, such as touch-based gesture control, the paper notes. Such functions usually rely on auxiliary sensors, such as accelerometers, gyroscopes and microphones that are available on many smart headphones
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"Dumb" headphones can be plugged into a HeadFi device that connects to a cellphone, turning them into intelligent headphones. Engineers are working on a smaller version of the device.
CREDIT
Siddharth Rupavatharam
HeadFi turns the two drivers already inside all headphones into a versatile sensor, and it works by connecting headphones to a pairing device, such as a smartphone. It does not require adding auxiliary sensors and avoids changes to headphone hardware or the need to customize headphones, both of which may increase their weight and bulk. By plugging into HeadFi, a converted headphone can perform sensing tasks and play music at the same time.
The engineers conducted experiments with 53 volunteers using 54 pairs of headphones with estimated prices ranging from $2.99 to $15,000. HeadFi can achieve 97.2 percent to 99.5 percent accuracy on user identification, 96.8 percent to 99.2 percent on heart rate monitoring and 97.7 percent to 99.3 percent on gesture recognition.
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Rutgers co-authors include Siddharth Rupavatharam, an electrical and computer engineering doctoral student, and Research Professor Richard E. Howard, the senior author and co-primary inventor at Rutgers' Wireless Information Network Laboratory (WINLAB), a research center in the School of Engineering. Engineers at the University of Science and Technology of China, University of Massachusetts Amherst, Microsoft and Alibaba Group contributed to the paper. A patent is pending.
CAPTION
The HeadFi prototype.
CREDIT
Siddharth Rupavatharam
Polarization: From better sunglasses to a better way of looking at asteroid surfaces
Unique technique may help planetary defense prepare for asteroids on a collision course with Earth
Using the same principles that make polarized sunglasses possible, a team of researchers at the Arecibo Observatory in Puerto Rico have developed a technique that will help better defend against asteroids on a collision course with Earth.
A new study recently published in The Planetary Science Journal found a better way to interpret radar signals bounced off asteroids' surfaces. The data can better tell us if an asteroid is porous, fluffy or rocky, which matters because there are hundreds of near-Earth asteroids that could potentially hit the planet.
"Learning more about the physical properties of asteroids is crucial in Planetary Defense," says Dylan Hickson the lead author and a research scientist at the Arecibo Observatory in Puerto Rico. "A porous, fluffy asteroid does not pose as much of an impact threat as a dense, rocky asteroid does. With our research we can better prepare for potential asteroid impact events.
Depending on their size and composition some asteroids will burn up in the atmosphere, but others could cause catastrophic damage. Knowing how to deflect these potential threats will depend on what we know about their makeup.
Data collected from 1999-2015 with the Arecibo's main dish in Puerto Rico were used to complete the study. Arecibo is a U.S. National Science Foundation facility, which UCF manages for NSF under a cooperative agreement with Universidad Ana G. Méndez and Yang Enterprises Inc. The main dish collapsed in December, but work continues throughout the rest of the facility, and scientists continue to use previously collected data.
"When we send a radar signal with Arecibo, we know the exact polarization of the light, but when it bounces off of a surface, that can change how it's polarized," Hickson says. "If the asteroid surface was a smooth mirror, for example, it will reverse polarization 'perfectly' when the signal is reflected. With a rough and rocky surface, the light will interact with rock edges, cracks, and grains -- and reflect in a completely different polarization."
When the team analyzed Arecibo data, they broke down the polarization of the received signal into various components to decipher what surface features produced them. Is more of the surface fine-grained, smooth dust, sand-like grains or big rocks? Or is the surface full of small rocks and fine grains of dust?
Using polarimetric decomposition (polarization technique) isn't new, but it isn't 100% reliable yet. For example, scientists on NASA's OSIRIS REx mission were surprised by how rocky asteroid Bennu was when they arrived last year to begin a sample collection mission. Images taken from the spacecraft found the surface to be much more rocky than initial radar data indicated, and the team had to adjust its sample target site.
"Our results provide a methodology to extract more information about the surface properties from observations, giving us a better picture of what these mysterious surfaces look like," Hickson says. "Not only can this methodology be applied to archival data, but it can also be applied to future observations, potentially vastly increasing our understanding of the broader asteroid population."
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Hickson is a postdoctoral research scientist in the Planetary Science Group at the Arecibo Observatory since 2019. He has a doctorate in Earth and space science from York University in Toronto, Canada and bachelor's degrees in Earth and environmental science and physical science from McMaster University in Hamilton, Canada.
The rest of the team on the paper includes: Anne K. Virkki and Phil Perillat from the Arecibo Observatory, Michael C. Nolan from the Lunar and Planetary Laboratory at the University of Arizona, and Sriram S. Bhiravarasu from Space Applications Centre in India.
Rainbows are some of the most spectacular optical phenomena in the natural world and Hawai'i has an amazing abundance of them. In a new publication, an atmospheric scientist at the University of Hawai'i at Mānoa makes an impassioned case for Hawaii being the best place on Earth to experience the wonder of rainbows. He begins by highlighting the Hawaiian cultural significance of rainbows, he reviews the science of rainbows and the special combination of circumstances that makes Hawai'i a haven for rainbows.
"The cultural importance of rainbows is reflected in the Hawaiian language, which has many words and phrases to describe the variety of manifestations in Hawai'i," said author Steven Businger, professor in the UH Mānoa School of Ocean and Earth Science and Technology. "There are words for Earth-clinging rainbows (uakoko), standing rainbow shafts (ka?hili), barely visible rainbows (punakea), and moonbows (a?nuenue kau po?), among others. In Hawaiian mythology the rainbow is a symbol of transformation and a pathway between Earth and Heaven, as it is in many cultures around the world."
Why is Hawai'i the rainbow capital of the world?
The essential ingredients for rainbows are, of course, rain and sunlight. To see a rainbow on flat ground the sun must be within about 40 degrees of the horizon. As the sun rises to higher angles in the sky during the morning, the height of the rainbow diminishes until no rainbow is visible above the horizon. The pattern is reversed as the sun lowers in the afternoon, with rainbows rising in the east and the tallest rainbows just prior to sunset.
Hawai'i's location in the subtropical Pacific means the overall weather pattern is dominated by trade winds, with frequent rain showers and clear skies between the showers.
Businger outlines four additional factors affecting the prevalence of rainbows throughout the islands.
"At night a warm sea surface heats the atmosphere from below, while radiation to space cools cloud tops, resulting in deeper rain showers in the morning that produce rainbows in time for breakfast," said Businger.
Another critical factor in producing frequent rainbows is Hawai'i's mountains, which cause trade wind flow to be pushed up, forming clouds and producing rainfall. Without mountains, Hawai'i would be a desert with a scant 17 inches annual rainfall.
A third factor conducive to rainbow sightings is daytime heating, which drives island-scale circulations. During periods of lighter winds, showers form over the ridge crests over Oahu and Kauai in the afternoon, resulting in prolific rainbows as the sun sets.
Due to the remoteness of the Hawaiian Islands, the air is exceptionally clean and free of pollution, continental dust, and pollen. This is the fourth factor that contributes to the numerous bright rainbows with the full spectrum of colors.
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Rainbow over Honolulu Harbor with what appears to be its reflection. However, the reflected bow is not what it appears to be. See the paper for explanation.
CREDIT
Minghue Chen
Chasing rainbows
As Businger pursued his passion for finding and photographing these beautiful light displays, he began to imagine a smartphone app with access to Doppler radar data and high-resolution satellite data that could alert users when nearby conditions become conducive for rainbow sightings.
"After a few years of false starts, Paul Cynn and I finally connected with Ikayso, a Hawaiian smartphone app developer in April of 2020. I am very excited to say that our app, called RainbowChase, is now available to the public for free," said Businger.
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RainbowChase is the only app that provides guidance to bring more rainbows into your life. Users can view radar and satellite images of rain and clouds, along with current and future weather, and collect rainbow photos.
CAPTION
An example of supernumerary bows beneath the primary bow.
