Fossil shows how penguins' wings evolved

A tiny fossil penguin plays a huge role in the evolutionary history of the bird, an international study shows.

Published in the Journal of the Royal Society of New Zealand, the study describes a new species of fossil penguin which lived in Otago about 24 million years ago.

Named Pakudyptes hakataramea, the penguin was very small -- about the same size as the little blue penguin, the smallest in the world -- with anatomical adaptations that allowed it to dive.

Lead author Dr Tatsuro Ando, formerly a PhD candidate at the University of Otago -- Ōtākou Whakaihu Waka and now at the Ashoro Museum of Palentology in Japan, collaborated with researchers from Otago, Okayama University of Science and Osaka University.

Dr Ando's inspiration for the paper came from discussions with the late Professor Ewan Fordyce, his supervisor and mentor at Otago.

Researchers analysed three bones -- a humerus, femur and ulna -- found by Professor Fordyce in the Hakataramea Valley, South Canterbury.

Dr Ando says Pakudyptes fills a morphological gap between modern and fossil penguins.

"In particular, the shape of the wing bones differed greatly, and the process by which penguin wings came to have their present form and function remained unclear," he says.

The humerus and ulna highlight how penguins' wings have evolved.

"Surprisingly, while the shoulder joints of the wing of Pakudyptes were very close to the condition of the present-day penguin, the elbow joints were very similar to those of older types of fossil penguins.

"Pakudyptes is the first fossil penguin ever found with this combination, and it is the 'key' fossil to unlocking the evolution of penguin wings."

Co-author Dr Carolina Loch, from Otago's Faculty of Dentistry, says analysis of the internal bone structure conducted at the Faculty of Dentistry, with comparison with data on living penguins provided from the Okayama University of Science, shows these penguins had microanatomical features suggestive of diving.

Modern penguins have excellent swimming abilities, largely due to their dense, thick bones that contribute to buoyancy during diving.

In Pakudyptes, the bone cortex was reasonably thick although the medullary cavity, which contains bone marrow, was open, similar to what we see in the modern little blue penguin, which tends to swim in shallow waters.

The ability for Pakudyptes to dive and swim comes down to the distinctive combination of its bones.

Bones such as the humerus and ulna show areas for attachment of muscles and ligaments which reveal how the wings were being used to swim and manoeuvre under water.

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Butterfly-inspired films create vibrant colors while passively cooling objects

On a hot summer day, white clothing feels cooler than other colors due to reflecting -- not absorbing -- sunlight. Other colors like blue or black, will undergo a heating effect as they absorb light. To circumvent this heating effect in colored cooling films, researchers drew inspiration from nanostructures in butterfly wings.

The new films, which don't absorb any light, could be used on the outside of buildings, vehicles and equipment to reduce the energy needed for cooling while preserving vivid color properties.

"In buildings, large amounts of energy are used for cooling and ventilation, and running the air conditioner in electric cars can reduce the driving range by more than half," said research team leader Wanlin Wang from Shenzhen University in China. "Our cooling films could help advance energy sustainability and carbon neutrality."

In Optica, Optica Publishing Group's journal for high-impact research, the researchers show that the films they developed lower the temperature of colorful objects to about 2 °C below the ambient temperature. They also found that when left outside all day, the blue version of the films was approximately 26°C cooler than traditional blue car paint. This represents an annual energy savings of approximately 1377 MJ/m2 per year.

"With our new films, excellent cooling performance can be achieved, no matter the desired color, saturation or brightness," said Wang. "They could even be used on textiles to create clothes of any color that are comfortable in hot temperatures."

Inspired by nature

A car with blue paint appears blue because it absorbs yellow light and reflects blue light. The large amount of light that is absorbed heats the car. Morpho butterflies, however, produce their highly saturated blue color based on the nanostructure of their wings. The design of the cooling nanofilm mimics these structures to produce vibrant colors that don't absorb light like traditional paint.

To create their Morpho-inspired nanofilms, the researchers placed a disordered material (rough frosted glass) under a multilayer material made of titanium dioxide and aluminum dioxide. They then placed this structure on a silver layer that reflects all light, thus preventing the absorption of solar radiation and the heating associated with that absorption.

The film's color is determined by how components within its multilayered structure reflect light. To create blue, for example, the multilayer material is designed to reflect yellow light in a very narrow range of angles while the disordered structure diffuses the blue light across a broad area.

Although this type of passive photonic thermal management has been accomplished before, it has only been used with white or clear objects because it is difficult to maintain a wide viewing angle and high color saturation.

Passive cooling of colorful objects

"Thanks to the layered structure we developed, we were able to extend the passive cooling method from colorless objects to colorful ones while preserving color performance," said Wang. "In other words, our blue film looks blue across a large range of viewing angles and doesn't heat up because it reflects all the light. In addition, high saturation and brightness can be achieved by optimizing the structure."

To test the new technology, the researchers created blue, yellow and colorless films, which they placed outdoors at Shenzhen University, on surfaces such as roofs, cars, cloth and cell phones, from 9 a.m. to 4 p.m. in both winter and summer. Using thermocouple sensors and infrared cameras to measure temperature, they found that the cooling films were more than about 15 ? cooler than the surfaces they were placed on in the winter and about 35 ? cooler in the summer.

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The dark cost of being toxic

An international research team including scientists from the Max Planck Institute for Chemical Ecology in Jena has discovered that the striking orange and black wings of monarch butterflies not only send the message to predators that these butterflies are highly toxic, but that the storage of toxins and development of the colourful wings come at a cost to the butterfly's body. The team reared monarch caterpillars on their milkweed food plants that had different levels of toxins. Monarchs that had ingested high levels of toxins from their food plants as caterpillars, experienced high levels of oxidative damage after storing these toxins in their bodies, and were less conspicuous in their coloration. The study demonstrated experimentally that the storing of toxins is costly for insects that are highly specialized on their food plants.

Monarch butterflies (Danaus plexippus) feed on milkweeds of the genus Asclepias when they are caterpillars, storing the plants' cardenolide heart poisons in their bodies for their own defence. The combination of the toxins with the striking orange and black wings of the monarch is called aposematism (derived from the Greek terms apo = away and sema = signal). Hannah Rowland head of the Max Planck Research Group on Predators and Toxic Prey at the Max Planck Institute for Chemical Ecology explains: "aposematism works because predators learn that eye-catching prey are best avoided. Predators learn faster when the visual signal is always the same. Bright orange means "`'don't eat me'. But other scientists and I have repeatedly found that aposematic animals can have varying degrees of warning signal strength, and we wondered what about pale orange, or deep orange? What does this mean, and what causes the difference?"

Rowland, together with her colleague Jonathan Blount from the University of Exeter, along with their international team of scientists, tested whether the storage of the plant's toxins is costly to the butterfly's body condition. Specifically, whether the storage of toxins causes oxidative stress, whichhappens when antioxidant levels are low. Because antioxidants can be used to make colourful pigments, they tested if the amount of toxins in the monarch is related to their conspicuousness and their oxidative state.

The researchers reared monarch caterpillars on four different milkweeds of the genus Asclepias that have different toxin levels. With this, they were able to manipulate the amount of toxins ingested to subsequently measure concentrations of cardenolides, determine oxidative state, and compare the resulting wing coloration.

"Monarch butterflies that sequestered higher concentrations of cardenolides experienced higher levels of oxidative damage than those that sequestered lower concentrations. Our results are among the first to show a potential physiological mechanism of oxidative damage as a cost of sequestration for these insects," says Hannah Rowland. The scientists also found that the colour of the wings of male monarchs depended on how much cardenolides they sequestered, and how much oxidative damage this had resulted in. Males with the highest levels of oxidative damage showed decreasing colour intensity with increased toxin uptake, while males with the least oxidative damage were the most toxic and colour intense.

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Scientists develop insect-sized flying robots with flapping wings

A new drive system for flapping wing autonomous robots has been developed by a University of Bristol team, using a new method of electromechanical zipping that does away with the need for conventional motors and gears.

This new advance, published today in the journal Science Robotics, could pave the way for smaller, lighter and more effective micro flying robots for environmental monitoring, search and rescue, and deployment in hazardous environments.

Until now, typical micro flying robots have used motors, gears and other complex transmission systems to achieve the up-and-down motion of the wings. This has added complexity, weight and undesired dynamic effects.

Taking inspiration from bees and other flying insects, researchers from Bristol's Faculty of Engineering, led by Professor of Robotics Jonathan Rossiter, have successfully demonstrated a direct-drive artificial muscle system, called the Liquid-amplified Zipping Actuator (LAZA), that achieves wing motion using no rotating parts or gears.

The LAZA system greatly simplifies the flapping mechanism, enabling future miniaturization of flapping robots down to the size of insects.

In the paper, the team show how a pair of LAZA-powered flapping wings can provide more power compared with insect muscle of the same weight, enough to fly a robot across a room at 18 body lengths per second.

They also demonstrated how the LAZA can deliver consistent flapping over more than one million cycles, important for making flapping robots that can undertake long-haul flights.

The team expect the LAZA to be adopted as a fundamental building block for a range of autonomous insect-like flying robots.

Dr Tim Helps, lead author and developer of the LAZA system said "With the LAZA, we apply electrostatic forces directly on the wing, rather than through a complex, inefficient transmission system. This leads to better performance, simpler design, and will unlock a new class of low-cost, lightweight flapping micro-air vehicles for future applications, like autonomous inspection of off-shore wind turbines."

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The wave beneath their wings

It's a common sight: pelicans gliding along the waves, right by the shore. These birds make this kind of surfing look effortless, but actually the physics involved that give them a big boost are not simple.

Researchers at the University of California San Diego have recently developed a theoretical model that describes how the ocean, the wind and the birds in flight interact in a recent paper in Movement Ecology.

UC San Diego mechanical engineering Ph.D. student Ian Stokes and adviser Professor Drew Lucas, of UC San Diego's Department of Mechanical and Aerospace Engineering and Scripps Institution of Oceanography, found that pelicans can completely offset the energy they expend in flight by exploiting wind updrafts generated by waves through what is known as wave-slope soaring. In short, by practicing this behavior, sea-birds take advantage of winds generated by breaking waves to stay aloft.

The model could be used to develop better algorithms to control drones that need to fly over water for long periods of time, the researchers said. Potential uses do not stop there.

"There's a community of biologists and ornithologists that studies the metabolic cost of flight in birds that can use this and see how their research connects to our estimates from theory. Likewise, our model generates a basic prediction for the winds generated by passing swell, which is important to physicists that study how the ocean and atmosphere interact in order to improve weather forecasting," Stokes said.

"This is an interesting project because it shows how the waves are actually moving the air around, making wind. If you're a savvy bird, you can optimize how you move to track waves and to take advantage of these updrafts. Since seabirds travel long distances to find food, the benefits may be significant," Lucas said.

Stokes and Lucas are, of course, not the first scientists to study the physics of the atmosphere that pelicans and other birds are hardwired to intuit so they can conserve energy for other activities. For centuries, humans have been inspired by the sight of birds harnessing the power and patterns of the winds for soaring flight.

That's how it started with Stokes, who is now in the second year of his PhD at UC San Diego. As a UC Santa Barbara undergraduate, Stokes, a surfer and windsurfer in his off hours, needed a project for his senior physics class and thought of the birds that would accompany him on the waves. When he looked closer, he appreciated the connection between their flight dynamics and the study of environmental fluid dynamics, a speciality of scientists at UC San Diego. The project ultimately turned into a master's thesis with Lucas, drawing inspiration from oceanographers at Scripps who seek to understand the interactions between the ocean and atmosphere.

Wave-slope soaring is just one of the many behaviors in sea-birds that take advantage of the energy in their environment. By tapping into these predictable patterns, the birds are able to forage, travel, and find mates more effectively.

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How hummingbirds hum

 The hummingbird is named after its pleasant humming sound when it hovers in front of flowers to feed. But only now has it become clear how the wing generates the hummingbird's namesake sound when it is beating rapidly at 40 beats per second. Researchers from Eindhoven University of Technology, Sorama, a TU/e spin-off company, and Stanford University meticulously observed hummingbirds using 12 high-speed cameras, 6 pressure plates and 2176 microphones. They discovered that the soft and complex feathered wings of hummingbirds generate sound in a fashion similar to how the simpler wings of insect do. The new insights could help make devices like fans and drones quieter.

The team of engineers succeeded in measuring the precise origin of the sound generated by the flapping wings of a flying animal for the first time. The hummingbird's hum originates from the pressure difference between the topside and underside of the wings, which changes both in magnitude and orientation as the wings flap back and forth. These pressure differences over the wing are essential, because they furnish the net aerodynamic force that enables the hummingbird bird to liftoff and hover.

Unlike other species of birds, a hummingbird wing generates a strong upward aerodynamic force during both the downward and upward wing stroke, so twice per wingbeat. Whereas both pressure differences due to the lift and drag force acting on the wing contribute, it turns out that the upward lifting pressure difference is the primary source of the hum.

The difference between whining, humming, buzzing and wooshing

Professor David Lentink of Stanford University: "This is the reason why birds and insects make different sounds. Mosquitoes whine, bees buzz, hummingbirds hum, and larger birds 'woosh'. Most birds are relatively quiet because they generate most of the lift only once during the wingbeat at the downstroke. Hummingbirds and insects are noisier because they do so twice per wingbeat."

The researchers combined all measurements in a 3D acoustic model of bird and insect wings. The model not only provides biological insight into how animals generate sound with their flapping wings, it also predicts how the aerodynamic performance of a flapping wing gives the wing sound its volume and timbre. "The distinctive sound of the hummingbird is perceived as pleasant because of the many 'overtones' created by the varying aerodynamic forces on the wing. A hummingbird wing is similar to a beautifully tuned instrument," Lentink explains with a smile.

High-tech sound camera

To arrive at their model, the scientists examined six Anna's hummingbirds, the most common species around Stanford. One by one, they had the birds drink sugar water from a fake flower in a special flight chamber. Around the chamber, not visible to the bird, cameras, microphones and pressure sensors were set up to precisely record each wingbeat while hovering in front of the flower.

You can't just go out and buy the equipment needed for this from an electronics store. CEO and researcher Rick Scholte of Sorama, a spin-off of TU Eindhoven: "To make the sound visible and be able to examine it in detail, we used sophisticated sound cameras developed by my company. The optical cameras are connected to a network of 2176 microphones for this purpose. Together they work a bit like a thermal camera that allows you to show a thermal image. We make the sound visible in a 'heat map', which enables us to see the 3D sound field in detail."

New aerodynamic force sensors

To interpret the 3D sound images, it is essential to know what motion the bird's wing is making at each sound measurement point. For that, Stanford's twelve high-speed cameras came into play, capturing the exact wing movement frame-by-frame.

Lentink: "But that's not end of story. We also needed to measure the aerodynamic forces the hummingbird's wings generates in flight. We had to develop a new instrument for that." During a follow-up experiment six highly sensitive pressure plates finally managed to record the lift and drag forces generated by the wings as they moved up and down, a first.

The terabytes of data then had to be synchronized. The researchers wanted to know exactly which wing position produced which sound and how this related to the pressure differences. Scholte: "Because light travels so much faster than sound, we had to calibrate each frame separately for both the cameras and the microphones, so that the sound recordings and the images would always correspond exactly." Because the cameras, microphones and sensors were all in different locations in the room, the researchers also had to correct for that.

Algorithm as a composite artist

Once the wing location, the corresponding sound and the pressure differences are precisely aligned for each video frame, the researchers were confronted with the complexity of interpretating high volume data. The researchers tackled this challenge harnessing artificial intelligence, the research of TU/e PhD student, and co-first author, Patrick Wijnings.

Wijnings: "We developed an algorithm for this that can interpret a 3D acoustic field from the measurements, and this enabled us to determine the most probable sound field of the hummingbird. The solution to this so-called inverse problem resembles what a police facial composite artist does: using a few clues to make the most reliable drawing of the suspect. In this way, you avoid the possibility that a small distortion in the measurements changes the outcome."

The researchers finally managed to condense all these results in a simple 3D acoustic model, borrowed from the world of airplanes and mathematically adapted to flapping wings. It predicts the sound that flapping wings radiate, not only the hum of the hummingbird, but also the woosh of other birds and bats, the buzzing and whining of insects and even the noise that robots with flapping wings generate.

Making drones quieter

Although it was not the focus of this study, the knowledge gained may also help improve aircraft and drone rotors as well as laptop and vacuum cleaner fans. The new insights and tools can help make engineered devices that generate complex forces like animals do quieter.

This is exactly what Sorama aims to do: "We make sound visible in order to make appliances quieter. Noise pollution is becoming an ever-greater problem. And a decibel meter alone is not going to solve that. You need to know where the sound comes from and how it is produced, in order to be able to eliminate it. That's what our sound cameras are for. This hummingbird wing research gives us a completely new and very accurate model as a starting point, so we can do our work even better," concludes Scholte.

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Butterfly wing clap explains mystery of flight

 

Silver-washed fritillary butterfly on flower.

The fluttery flight of butterflies has so far been somewhat of a mystery to researchers, given their unusually large and broad wings relative to their body size. Now researchers at Lund University in Sweden have studied the aerodynamics of butterflies in a wind tunnel. The results suggest that butterflies use a highly effective clap technique, therefore making use of their unique wings. This helps them rapidly take off when escaping predators.

The study explains the benefits of both the wing shape and the flexibility of their wings.

The Lund researchers studied the wingbeats of freely flying butterflies during take-off in a wind tunnel. During the upward stroke, the wings cup, creating an air-filled pocket between them. When the wings then collide, the air is forced out, resulting in a backward jet that propels the butterflies forward. The downward wingbeat has another function: the butterflies stay in the air and do not fall to the ground.

The wings colliding was described by researchers almost 50 years ago, but it is only in this study that the theory has been tested on real butterflies in free flight. Until now, the common perception has been that butterfly wings are aerodynamically inefficient, however, the researchers suggest that the opposite is actually true.

"That the wings are cupped when butterflies clap them together, makes the wing stroke much more effective. It is an elegant mechanism that is far more advanced than we imagined, and it is fascinating. The butterflies benefit from the technique when they have to take off quickly to escape from predators," says biology researcher Per Henningsson, who studied the butterflies' aerodynamics together with colleague Christoffer Johansson.

"The shape and flexibility of butterfly wings could inspire improved performance and flight technology in small drones," he continues.

In addition to studying the butterflies in a wind tunnel, the researchers designed mechanical wings that mimic real ones. The shape and flexibility of the mechanical wings as they are cupped and folded confirm the efficiency.

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