Birds have an incredible ability to fly at high altitudes, even above the height that airplanes typically fly. But not all birds are capable of flying so high up. A bird’s ability to fly at altitude is determined by several factors.
How high can birds fly?
Some birds can fly remarkably high. The highest flying bird ever recorded was a Ruppell’s griffon vulture, which collided with a commercial airliner at 37,000 feet in 1973 over Ivory Coast in West Africa. That’s over 7 miles high! Other birds that have been recorded at extremely high altitudes include the bar-headed goose, which has been seen flying over the Himalayas above 29,000 feet, and a flock of whopping cranes that was witnessed flying at 30,000 feet over Saudi Arabia.
In general, smaller birds fly closer to the ground while larger birds with broader wingspans are more suited for high altitude flight. The largest birds capable of the highest sustained flights are condors, vultures, geese, swans, cranes, and pelicans.
Why do some birds fly so high?
Birds may fly to great heights for several reasons:
- Searching for food – Vultures and other scavenging birds may scan vast areas from high above to spot food sources.
- Migration – Many migratory birds travel enormous distances and utilize high flying air currents to help cover those distances more efficiently.
- Avoiding threats – By getting very high, some birds can avoid predators and threats that exist closer to the ground.
Challenges of high altitude flight
Flying at extremely high altitudes presents several physiological challenges for birds:
- Oxygen deprivation – As altitude increases, there is less oxygen available. Many high flying birds have adapted through larger lungs and more efficient respiratory systems.
- Freezing temperatures – Temperatures decrease by about 3.5° F per 1,000 feet gained in altitude. Birds need effective insulation and the ability to raise their metabolic rate to generate heat.
- Wind and weather – The winds and conditions common at high altitudes require physical adaptations to maintain control and avoid being blown off course.
Adaptations that enable high altitude flight
Birds capable of very high altitude flight possess a range of adaptations that allow them to overcome the challenges faced at elevation:
- Strong flight muscles and large wingspans generate enough thrust and lift.
- An efficient oxygen circulation system moves oxygen into the blood and tissues.
- Hemoglobin with a higher affinity for oxygen in the blood.
- A larger lung capacity compared to the body size.
- Denser networks of capillaries to facilitate gas and nutrient exchange.
- The ability to increase metabolic rate and generate more internal body heat when needed.
How high do commercial aircraft fly in comparison?
Most commercial airliners cruise at altitudes between 30,000 and 42,000 feet. This is more fuel efficient for the planes and provides a smoother ride for passengers. So many high flying birds can reach or even exceed the cruising altitudes of planes carrying hundreds of people!
The highest altitude ever attained by a commercial aircraft was a Concorde supersonic jet that reached 60,000 feet in 1996. No bird has ever been recorded flying quite that high in sustained flight.
Aircraft | Typical Cruising Altitude |
---|---|
Small prop planes | Up to 14,000 feet |
Large passenger jets | 30,000 – 42,000 feet |
Concorde supersonic jet (retired) | Up to 60,000 feet |
Can all birds fly at high altitudes?
No, not all birds are physiologically capable of flying at very high elevations. Some key factors that determine how high a bird can fly include:
- Wingspan – Broad wings with large surface area improve lift at altitude.
- Wing shape – Long, pointed wings provide an aerodynamic advantage.
- Heart and lung capacity – Delivers oxygen to working muscles.
- Hemoglobin levels – Increased hemoglobin improves oxygen transport.
- Body size – Larger birds fare better than smaller ones in thin air.
- Metabolism – Ability to generate heat helps counter frigid temperatures.
Songbirds like sparrows and finches tend to max out below 10,000 feet elevation. Small birds lose heat quickly and have a harder time flying in the thinner atmosphere up high.
Heavy birds like chickens, ostriches, and penguins are also low flyers unsuited for high elevation flight. Their wing size and shape are not built for flying long distances at altitude.
Highest flying bird species
Among the highest flying birds are several large raptor species. These include:
- Golden eagle – Recorded at elevations over 36,000 feet.
- Bald eagle – Spotted at over 10,000 feet.
- Lammergier – Flies around mountain peaks over 16,000 feet.
- Griffon vulture – Can reach 37,000 feet but more often flies between 10,000-15,000 feet.
Waterfowl that migrate long distances and fly very high include:
- Bar-headed goose – Flies over the Himalayas at 29,000+ feet.
- Whooper swan – Documented flying over 29,000 feet.
- Mallard duck – Often migrates between 6,000-9,000 feet.
Influence of weather conditions on flight altitude
Weather patterns and atmospheric conditions have a significant influence on the flight altitudes birds can reach on a given day. Some key factors:
- Wind speed – Stronger winds at higher elevation give birds added lift and save energy.
- Wind direction – Tailwinds allow birds to fly higher more easily.
- Humidity – Drier air makes it easier to stay aloft than dense, humid air.
- Clouds and rain – May keep birds lowered either for visibility or to avoid icing.
- Air pressure – Birds ascend to where air density matches their wings’ lift capacity.
Birds also take advantage of thermal columns of rising warm air, allowing them to ascend higher before extending their wings and gliding considerable distances.
How weather limits altitude
Adverse weather can hamper a bird’s ability to reach great heights. Some examples:
- Strong headwinds require more flapping and make sustaining altitudes over 20,000 feet challenging.
- Turbulence and updrafts can batter birds and force them to fly lower.
- Thunderstorms often contain heavy rain, lightning, and gusty shifting winds that can knock birds off course.
- Icing from freezing rain causes issues with stability and additional weight.
Effects of exceeding a bird’s altitude limits
If a bird pushes beyond its physiological altitude limits, it faces some risks and negative effects:
- Oxygen deprivation causing hypoxia – Disorientation, loss of consciousness possible.
- Freezing temperatures – Can lead to frostbite on wings, feet, eyes, etc.
- Stalled muscles – Insufficient oxygen to power wings can cause sudden drops.
- Increased heart rate – Working harder in thin air stresses the cardiovascular system.
- Water loss – The body rapidly loses moisture in the dry upper atmosphere.
Birds that exceed their vertical limits too much can become dizzy, immobilized, or even die from oxygen deprivation. Most birds avoid going beyond what their bodies can handle through instinctual limits.
Emergency descents
When pushed beyond its limits, a bird may perform an emergency descent to a lower altitude with more oxygen. This rapid plunge, often accompanied by frantic flapping, allows the bird to quickly reach a safer elevation before injury or loss of consciousness occurs.
Conclusion
The ability of many birds to fly at extremely high altitudes is a remarkable feat of biology and evolution. Their specialized cardiovascular and respiratory systems allow sustained flight above elevations where humans require supplemental oxygen. While not all bird species can reach such heights, iconic high flyers like vultures, geese, and eagles are among the highest soaring aviators in the sky.