Birds have amazed humans with their ability to fly for thousands of years. While all birds use their wings for flight, there are actually two distinct types of flight used by birds – flapping flight and soaring flight. Both allow birds to become airborne and cover large distances, but achieve lift and forward propulsion in different ways.
What is soaring?
Soaring is a type of flight where birds utilize air currents to gain altitude and remain airborne without flapping their wings. It allows birds to conserve energy as they ride rising air currents called thermals to gain height. Once at a sufficient altitude, they can then glide long distances before finding the next thermal to soar upwards again. Soaring birds minimize flapping and make use of environmental factors like thermals and ridge lifts to remain aloft.
Many large birds utilize soaring flight including hawks, eagles, vultures, albatrosses, and condors. These birds tend to have long, broad wingspans ideal for soaring. Their wings are shaped to provide substantial lift and allow them to carve smooth turns within columns of rising air. Soaring birds often hold their wings in a slight dihedral, or upward “V” shape to remain balanced on air currents.
How do birds soar?
There are a few different soaring techniques used by birds:
- Thermal soaring – Circling upward within columns of warm rising air called thermals. Thermals form over land on sunny days when the ground warms the air above it. Birds will circle within these rising air pockets to gain altitude.
- Ridge soaring – Gliding parallel along a ridge or mountainside. Wind deflects upwards along the ridge slope, providing lift for soaring birds. They can continue to fly along the ridge without flapping.
- Convergence soaring – Soaring in wind columns where two winds meet and are forced upwards. This occurs above boundaries between land/water or forests/clearings.
- Wave soaring – Riding rising and sinking air currents formed by winds blowing across a mountain range. Skilled birds can traverse back and forth between waves to cover great distances.
What is powered flight?
In contrast to soaring, powered flight refers to flapping flight where birds generate both lift and thrust by flapping their wings. Rather than utilizing air currents for lift, birds produce lift through wing flapping. The downward stroke of the wings provides lift while the upward stroke provides forward thrust. Powered flight relies on the bird’s own energy output rather than exploiting environmental air currents.
Many smaller bird species utilize powered flight including songbirds, pigeons, ducks, and hummingbirds. Their wings tend to be shorter and more rounded compared to soaring birds. The rapid flapping creates airflow over the wings to provide sustained lift. These birds usually flap constantly with minimal gliding.
Adjustments for powered flight
Birds make small adjustments during powered flight to control direction and orientation:
- Angle of attack – Adjusting the angle at which the wings meet the oncoming air. A higher angle provides more lift while a lower angle provides less.
- Camber – Adjusting the curve of the wings from flat to more curved. More curved wings provide more lift.
- Wing loading – Bringing wings closer to the body decreases surface area and lift. Extending wings increases area and lift.
- Stalling – Feather separation on the upper wing disrupts airflow and causes loss of lift. Allows for quick descent.
Key differences between soaring and powered flight
While both soaring and flapping flight allow birds to become and stay airborne, there are several key differences between these two types of avian flight:
Soaring Flight | Powered Flight |
---|---|
Uses air currents and wind deflection for lift | Produces own lift via wing flapping |
Long, broad, cambered wings work best | Shorter, rounded wings allow rapid flapping |
Minimal flapping and energy expenditure | Constant flapping requires high energy |
Best for large birds like eagles and hawks | Best for smaller birds like songbirds |
Soar within thermals, along ridges, etc. | Make subtle angle and shape adjustments |
Primarily a gliding motion | Alternating downward and upward strokes |
Energy efficiency
One of the main reasons large birds soar is to conserve energy. Flapping flight requires a huge amount of energy output from birds. Soaring allows them to travel great distances while minimizing wing flapping. Birds of prey like eagles and hawks can rely almost entirely on soaring and gliding while hunting rather than flapping constantly. The use of updrafts and ridge lifts allows them to search wide areas while expending minimal effort. Soaring flight essentially outsources lift production to the atmosphere and terrain rather than the bird’s muscles.
Maneuverability
In powered flight, birds can maneuver with great precision by adjusting wing angles, camber, and loading. The constant adjustments create very nuanced control of speed, direction, and orientation. Soaring birds have less maneuverability and are more dependent on wind patterns. However, their long, stiff wings are very well-adapted for soaring flight and provide excellent performance once aloft within an updraft. So each flight style suits the needs of different types of birds.
Unique examples
A few birds showcase the incredible spectrum of powered flight versus soaring flight:
Hummingbirds
Hummingbird flight represents an extreme form of powered flight. Their tiny size and incredibly high metabolism requires near-constant flapping. Their wingbeat frequency can approach 80 beats per second! While tiny, inefficient for soaring, their small size allows great agility and precise hovering in place.
Albatrosses
Albatrosses epitomize soaring birds thanks to their enormous wingspans up to 11 feet! They utilize a dynamic soaring technique to perform long sinuous glides over ocean swells without flapping for great distances. Their wings provide enough lift that they only need land to raise their young.
Geese
Geese are remarkably efficient fliers thanks to their typical V-formation during migration. The flapping of the lead bird creates uplift for the followers, so the trailing birds expend less energy. The birds take turns being the leader. This cooperative powered flight allows geese to fly great distances.
Penguins
Unlike other birds, penguins have forewings specialized for swimming in water, not flying in air. Their wings provide propulsion and steering underwater where their body is buoyant. On land, their wings are too small for flight. However, penguins can still become airborne by using powered flight to leap out of the water onto land or ice.
Conclusion
Birds utilize two main forms of flight – soaring on air currents and powered flapping flight. Soaring allows large birds like eagles to minimize energy expenditure by riding thermals and wind patterns. Smaller birds like songbirds flap constantly to generate their own lift and propulsion. Both types achieve flight but in different ways optimized for the size and hunting needs of diverse bird species. Flight provides an enormous evolutionary advantage but requires adaptations to either the bird’s body or behavior.