science

Stunning video shows how owls fly by creating swirling vortices of air beneath their wings


STUNNING video shows an owl passing through a cloud of tiny helium bubbles in ultra slow motion, revealing how birds stay aloft by creating small circular flows of air beneath their wings

  • Scientists at the Royal Veterinary College outside London studied bird flight
  • They filmed two owls and a hawk as they flew through small helium bubbles
  •  The slow motion recording show small vortices of air keeping the birds aloft

A new study has captured the mechanics of how birds fly, by creating small vortices or rotating air with their wing flaps and tail movements.

To study the aerodynamics of bird flight, a group of scientists at the Royal Veterinary College in Hatfield, England, just outside London, recorded three different kinds of birds flying through a specially designed flight corridor.

The birds selected for the study were a female barn owl, a male tawny owl, and a female northern goshawk.

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Researchers at the Royal Veterinary College in Hatfield, England recorded two owls and a hawk as they flew through a fine mist of helium bubbles to study they aerodynamics of bird flight

Researchers at the Royal Veterinary College in Hatfield, England recorded two owls and a hawk as they flew through a fine mist of helium bubbles to study they aerodynamics of bird flight

The flight corridor measured just under six feet tall and six feet wide, and was painted completely black to make the birds standout.

The birds flew a short distance between two human handlers, passing through a fine mist of helium bubbles in the middle, which was illuminated with LED lights as soon as the birds passed through, allowing the team to record the exact motion of the air produced by the bird wings.

The flight corridor was carefully assembled to prevent any ambient movement of air that might disrupt the readings, while the birds selected all had experience in brightly lit environments such as film sets.

As the birds passed through the mist of helium bubbles, there were recorded by ultra slow motion cameras and an advanced 4D particle tracking program that allowed the team to measure the movement of each helium particle.

Interpreted the wake structure left by the different birds to understand how they navigate and maneuver through the air

The volume of helium bubbles were designed to not be illuminated with external lights until after the birds had passed through them.

They captured the motion of the helium bubbles with cameras and an advanced 4D particle tracking software, which could chart the movement of each helium bubble.

The recordings showed that with each bird, the wings produced two circular vortices, one moving clockwise and another moving counterclockwise, both of which provided lift to keep the birds aloft.

A second pair of smaller vortices were also created in the wake of the tail, which would rotate upward if the tail was angled upward, or downward when the tail angled downward.

The team used ultra slow motion cameras and a special 4D particle tracking software that allowed them to follow the movements of all the helium bubbles as they were swept up in the circular flows of air

The team used ultra slow motion cameras and a special 4D particle tracking software that allowed them to follow the movements of all the helium bubbles as they were swept up in the circular flows of air

The team found the birds produced two sets of clockwise and counterclockwise vortices that helped keep the birds aloft

The team found the birds produced two sets of clockwise and counterclockwise vortices that helped keep the birds aloft

The blue streaks represent clockwise vortices of air and the red streaks represent counterclockwise vortices of air, and the central streaks show the vortices produced in the wake of the bird's tails

The blue streaks represent clockwise vortices of air and the red streaks represent counterclockwise vortices of air, and the central streaks show the vortices produced in the wake of the bird’s tails

The team said their results 'are not surprising, and entirely match expectations from aerodynamic theory and experience from aeronautics.'

The team said their results ‘are not surprising, and entirely match expectations from aerodynamic theory and experience from aeronautics.’

These four rotating vortices of air helped give each bird the necessary amount of lift to stay airborne, while allowing it make subtle shifts to remain level.

According to the study, which was published this month in the Journal of Experimental Biology, the results ‘are not surprising, and entirely match expectations from aerodynamic theory and experience from aeronautics.’

The team suggests that further study could help provide insight into full stability mechanics birds use while in flight, but the captured air flow data suggests the general principles of aerodynamics apply to birds just as you would expect.

WHY DO MIGRATING BIRDS FLY IN A V-FORMATION?

Birds fly in a v-formation to help them fly more efficiently, staying aloft while expending as little energy as possible.

Scientists learned the aviation secrets of migrating birds after attaching tiny logging devices to a flock of 14 northern bald ibises that not only tracked their position and speed by satellite but measured every flap of their wings.

The 14 birds used in the study were hand-reared at Vienna Zoo in Austria by the Waldrappteam, an Austrian conservation group that is re-introducing northern bald ibeses to Europe. 

Birds fly in a v-formation to help them fly more efficiently, staying aloft while expending as little energy as possible (stock image)

Birds fly in a v-formation to help them fly more efficiently, staying aloft while expending as little energy as possible (stock image)

The birds were studied as they flew alongside a microlight on their migration route from Austria to their winter home in Tuscany, Italy.

Lead researcher Dr Steve Portugal, from the Royal Veterinary College, University of London, said: ‘The distinctive V-formation of bird flocks has long intrigued researchers and continues to attract both scientific and popular attention, however a definitive account of the aerodynamic implications of these formations has remained elusive until now.

‘The intricate mechanisms involved in V-formation flight indicate remarkable awareness and ability of birds to respond to the wingpath of nearby flock-mates. Birds in V-formation seem to have developed complex phasing strategies to cope with the dynamic wakes produced by flapping wings.’

When flying in a V formation, the birds’ wing flaps were approximately ‘in-phase’, meaning all the wing tips followed roughly the same path, the scientists found. 

This helped each bird capture extra lift from the upwash of its neighbour in front.

Occasional shifts of position within the formation meant that at times birds flew directly one behind the other. 

When this happened, the birds altered their wing beats to an out-of-phase pattern to avoid being caught by downwash.

 



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