Owls' wings could hold the key to beating wind turbine noise

Date:  July 4, 2017

Source:  IOP Publishing

Summary:  Inspiration from owls' wings could allow aircraft and wind turbines to become quieter, suggests a new study. Researchers studied the serrations in the leading edge of owls' wings, gaining new insight into how they work to make the birds' flight silent. Their results point towards potential mechanisms for noise suppression in wind turbines, aircraft, multi-rotor drones and other machines.

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Watch: This Little Bird Can Sing With Its Wings

The broadbill's strange song may set your heart aflutter.

    

By Ashley P. Taylor

March 30, 2016

Most birds have to open their beaks to sing, but when it comes to the dainty broadbill, all it has to do is wiggle its wings. In African and Rufous-sided Broadbills, circular flight displays (see the video below) are accompanied by a pulsing song that can be heard from more than 300 feet away. The brreeeeet sound, which resembles a klaxon horn, doesn’t come from vocalizations, but rather from the fluttering of wing feathers, as explained in a study published today in the Journal of Experimental Biology.

Some types of birds, such as hummingbirds and doves, can sing with both their syrinx—the avian equivalent of a voicebox—and their wings and tails, says study author Christopher Clark, a researcher at the University of California, Riverside. Clark knew that broadbills make some pretty cool noises, too, but wasn't sure whether they came from the bill or the feathers.

To find out, Clark and his colleagues traveled to Uganda to take video and audio recordings of African and Rufous-sided Broadbills during their circular flight—a behavior the scientists speculate might be for romancing and defending territory. Back in the lab, they analyzed the clips and correlated the sound pulses with the down strokes of the wings. The scientists also noticed gaps between a handful of the 10 primary feathers—located at the outermost part of the wing and connected to the bird’s wrist bone.

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Small vortex on wing makes the elegance of birds' flight

Date:

June 5, 2015

Source:

Laboratory of Behavioral Ecology and Evolution at Seoul National University

Summary:

Birds use a thumb-like structure on the wing to create a small vortex which makes their turns and landings smooth, new research shows. This is the first time that researchers have found evidence that the effect of the alula is due to a small vortex formed at the tip of the alula feathers.

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How dinosaur arms turned into bird wings

Date:

September 30, 2014

Source:

PLOS

Summary:

Although we now appreciate that birds evolved from a branch of the dinosaur family tree, a crucial adaptation for flight has continued to puzzle evolutionary biologists. During the millions of years that elapsed, wrists went from straight to bent and hyperflexible, allowing birds to fold their wings neatly against their bodies when not flying. A resolution to this impasse is now provided by an exciting new study.

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Bird Fingers: Understanding Evolution Of Wings In Our Avian Friends

Brett Smith for redOrbit.com – Your Universe Online

While birds’ three fingers appear analogous to our own thumb, index and middle fingers, embryonic evidence has shown that the “pinky” side of a bird’s claw develops first, which some theories have said is evidence of the three bird fingers being an index, middle and ring finger.

According to a new study published in the Journal of Experimental Zoology, as dinosaurs evolved into birds, they actually lost their pinky and thumb, making bird fingers an index, middle and ring finger.

The earliest known bird, Archaeopteryx, has fingers that resemble those of the dinosaur Deinonychus, a probable relative. According to fossil analyses, two fingers on the pinky-side of the hand were reduced over the generations in the ancestor of Deinonychus. This evidence supports the identification of these fingers in birds as a thumb, index, and middle finger identification. Also, the genes active in the development of the first bird finger match up with genes in the developing thumb of other animals, and not those of the index finger.

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The Secrets of Owls' Near Noiseless Wings

Nov. 24, 2013 — Many owl species have developed specialized plumage to effectively eliminate the aerodynamic noise from their wings -- allowing them to hunt and capture their prey in silence.

A research group working to solve the mystery of exactly how owls achieve this acoustic stealth will present their findings at the American Physical Society's (APS) Division of Fluid Dynamics meeting, held Nov. 24 -- 26, in Pittsburgh, Pa. -- work that may one day help bring "silent owl technology" to the design of aircraft, wind turbines, and submarines.

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Hummingbirds' wings 'shape-shift'

By Victoria Gill Science reporter, BBC News, Valencia, Spain

Footage shot with high-speed cameras has revealed how hummingbird wings bend and flex, to keep the birds in the air.

Masateru Maeda, a PhD student at Chiba University in Japan, captured the footage.

The ultimate aim of his measurements of the movements of the wings is to copy their function in the design of flying robots.

The scientist presented his findings at the Society for Experimental Biology's annual meeting in Valencia, Spain.

The researchers captured their footage at Tama Zoological park in Tokyo.

As birds and insects move through the air, their wings are held at a slight angle, which deflects the air downward.

This deflection means the air flows faster over the wing than underneath, causing air pressure to build up beneath the wings, while the pressure above the wings is reduced. It is this difference in pressure that produces lift.

Flapping creates an additional forward and upward force known as thrust, which counteracts the insect's weight and the "drag" of air resistance.

The downstroke or the flap is also called the "power stroke", as it provides the majority of the thrust. During this, the wing is angled downwards even more steeply.

You can imagine this stroke as a very brief downward dive through the air - it momentarily uses the weight of the animal's own weight in order to move forwards. But because the wings continue to generate lift, the creature remains airborne.

In each upstroke, the wing is slightly folded inwards to reduce resistance.

The team chose hummingbirds as their "wing model" because they can be studied so easily; they hover quite still as they feed on nectar.

"And they're very small," added Mr Maeda. "Larger birds that cannot hover have to be studied in wind tunnels."

But to get his footage, Mr Maeda had to work in the glasshouse of the zoo, which is kept at 35C for the birds and butterflies that live there.

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