Last updated on November 12th, 2021 at 11:22 pm
Many of us look up to the sky and envy how birds can soar without a care in the world. However, not many of us ponder can birds fly without wind? How do birds fly even on a still and windless day?
Birds can fly without wind because their flight is determined by lift, the force that opposes the weight of their wings. When there is enough aerodynamic force and air pressure, a bird will be able to fly in the air, even without wind, for extended periods.
How Birds Can Fly Without Wind
Birds have hollow bones that are lightweight but strong. Due to this, they can take flight by cutting through the air with their wings.
Kim Bostwick, a scientist for the Cornell Lab of Ornithology, compares the flight of birds to moving your hand in water.
Bostwick states that if you move your open palm through the water, you’ll have trouble moving through the water.
However, you can move your hand and use it to slice through the water with ease.
The same thing happens with bird’s wings as they are positioned to cut through the wind with ease.
The main benefit of a bird’s wing design is that the air flows over the wing and faster on top due to the curved top.
When this happens, more air can pass through the bottom of the bird’s wing, pushing the bird upward and lifting the animal.
Hence, a bird will be able to fly without wind due to the constant source of airflow. However, there is one catch.
Most of the time, lightweight birds will be able to do this, but heavier ones may have more difficulties.
What ‘Lift’ Means for Flight
In aerodynamics, the lift is a term used to explain the mechanical force generated by an object moving through the air.
There are four critical influences to aerodynamics: lift, drag, thrust, and weight. However, birds are not mechanical objects, so they play by slightly different rules.
Lift is the force that opposes the weight of an object and holds it in the air. Most lift is generated by wings and is produced from the bird’s motion flying through the air.
Lift is a force, which is impacted by magnitude, direction, and weather.
Aside from that, the breed of the bird can also affect the impact of wind and flight. Different breeds of birds have varying bone wing structures and sizes.
These also impact how much lift a bird can produce.
How is Lift Generated?
Bird’s wings are shaped uniquely so that the distance from the front to the back over the top of the wings is bigger than the distance under the wings.
Having a long distance on top enables the air to move faster on the top of the wing to equal the speed of the lower side of the wing.
This is called the Bernoulli effect and helps produce enough lift force that outweighs a bird’s weight and enables them to fly.
To break it down in simpler terms, the lift is generated by the flapping wings and will keep the bird floating in the air.
This is mainly due to birds’ wings being designed to slice through the air and keep them propelled. Of course, the bird’s size, weight, and other factors come into play.
How Wind Influences Flight
Wind does help a bird fly, but it has less influence on whether the bird can fly at all. Wind can help a bird stay propelled in the air, but its wings are used to create lift.
The lift doesn’t rely on the wind but rather a mass of air in the atmosphere.
To simplify this, a bird does not need wind to fly. The wind is the movement of the air mass, but a bird doesn’t require movement.
They need any air mass to stay afloat, including air mass that they create by flapping their wings. As long as there is dense air mass, a bird can generate lift and fly.
The only factor that changes when there is wind present is that the bird’s speed will increase.
That’s because the faster air moves across a bird’s wing, the more lift it produces and the faster the bird will go.
So, while lift is an important factor, it’s not the only factor that affects a bird’s speed.
Types of Flying
There are three known methods birds use to fly. Each of these methods is categorized by its wing motion. Here is a general breakdown of how each flight works.
Gliding Flight
Gliding flight works when the upward aerodynamic force is the same as the bodyweight of the bird.
When gliding, a bird’s wings will deflect air down which causes the bird to lift up through the air.
Air resistance and drag can cause the bird to slow down, but they will still stay afloat in the sky.
Birds who are using this type of flight don’t use propulsion to keep themselves in the sky.
Instead, the energy lost due to the aerodynamic drag uses the potential energy of the bird. This is what is known as descending flight or soaring flight.
Flapping Flight
Flapping flight uses the bird’s wings as opposed to gliding flight. Instead of relying on potential energy, the bird uses its flapping wings to develop lift.
The lift rotates forward and helps provide thrust, which in turn counteracts any drag from atmospheric pressure.
Then, the speed increases, which also increases lift more and helps offset the bird’s body weight.
There are two types of flapping flight, down-stroke and up-stroke. The down-stroke creates the most thrust.
The up-stroke folds inwards and reduces the energy used by the bird. In turn, this also reduces some thrust.
Bounding Flight
Bounding flight, or flap-bounding flight, is used by small birds to travel long distances.
This technique allows short bursts of wing flapping at alternative intervals to keep the bird propelled in the air.
The bird’s wing will then fold inwards towards itself and rest against its body mid-flight.
When the wings of a bird are folded, its flight becomes ballistic and decreases the energy required to maintain flight.
This, in turn, allows them to fly for more extended periods without flapping their wings frequently.