The vast majority of birds are capable of flight, but a few species take their flying talents to another level.
Some birds can fly at incredible altitudes equalling or exceeding that of planes. In fact, some species have even been spotted out of the window of jet airliners! So, why and how can birds fly at high altitudes?
When migrating, flying at higher altitudes requires less effort as the air is thinner and air resistance is lower, the same principle as to why commercial airliners also cruise at high altitudes. In addition, some non-migratory birds like eagles and vultures fly at high altitudes to give them a wide birds eye view of the terrain below them, enabling them to pick out prey across a wide area.
There are just a handful of birds that can fly at altitudes exceeding 20,000ft, or 6,000m, and just two or three are capable of flying at altitudes exceeding 30,000ft, or 9,100m. That’s similar to a commercial airliner at cruising height or higher than Mount Everest.
Read on to discover why and how birds fly at altitudes, and what birds top the list of the highest-flying birds in the world!
A flock of birds flying high against the sunset
Three birds are capable of flying at heights exceeding 30,000ft. The record-holder is the Rüppell's vulture, an uncommon bird that is found primarily in East Africa.
These birds regularly fly at altitudes exceeding 20,000ft, or 6,000m, but in extreme cases, they’ve been recorded soaring to an incredible 37,000ft, or 11,277m.
A Rüppell's vulture was recovered from the engine of a commercial airliner over the Ivory Coast in 1973, which caused the engine to fail and forced the pilot to make an emergency landing.
To put that altitude in perspective, it’s 2,500m higher than Mount Everest, around 30 times higher than the Empire State Building, or equivalent to 471 full-size tennis courts.
Rüppell's Vulture or Rüppell's Griffon Vulture (Gyps Rueppelli) are one of, if not, the highest flying birds in the world
In second place, the Common crane can fly at altitudes of around 33,000ft, or 10,000m. This enables them to migrate over the Himalayas, where you can spot them in Spring and Fall.
Common Cranes can reach altitudes of around 33,000ft
In third, the Bar-headed goose can fly at around 29,000 to 30,000ft or approximately 9,100m. Again, their migratory journey takes them over the Himalayas.
Whooper swans are up there too, completing tremendous migratory journeys of thousands of miles at an altitude of 27,000ft, or 8,200m.
Perhaps one of the least likely high-altitude flyers is the Mallard duck, recorded flying at an altitude of 21,000ft, or 6,400m, in Nevada, USA.
A pair of bar-headed geese in flight
There are two main scenarios for when birds fly high - for migration and whilst on the lookout for prey.
Firstly, birds fly at high altitudes during migration. The air is thinner the further up you go, which lowers air resistance and makes flying more mechanically efficient.
Secondly, birds fly at high altitudes to gain a wide view of the ground, which is advantageous when looking out for prey. For example, the Rüppell's vulture regularly flies in circles at a great height to scan the desert for carrion.
While flying at a high altitude is more efficient than flying at a low altitude, most animals, including humans, would perish at altitudes exceeding 30,000ft without serious acclimatization at least.
At the earth's surface, the air's oxygen content generally varies between 20 and 19%. At 30,000ft, oxygen levels drop to just 6%.
High-flying birds are excellent at absorbing oxygen at this altitude, but it still requires huge amounts of energy. Some birds, such as geese, swans, and cranes, lose 15 to 20% of their body weight throughout their migratory journey!
If birds fly too high without adequate energy, they’ll have to return to a lower altitude and rest.
Swans can lose up to 20% of their body weight during migration
Birds often collide with planes. In fact, it even has its own terminology, a “bird strike”. There are an estimated 13,000 bird strikes each year in the US alone, but 65% result in no damage to the aircraft.
Geese are a prime culprit, accounting for the majority of bird strikes in the US, but starlings, pigeons, and vultures are all common.
Commercial airliners are built with failsafes for when an engine ingests a bird, and even if the engine fails or is shut down automatically, the airliner is typically able to land without much issue.
However, there have been a few fatal incidents of birds colliding with planes, including on October 4, 1960, when a Lockheed passenger plane flew into a flock of starlings, causing all four engines to fail. It crashed shortly after, killing 62 out of 72 passengers. Birds have even struck space shuttles and military aircraft. Luckily, the risk of dying from a bird strike is less than 1 in 1 billion flying hours.
A flock of migratory geese with a plane in the background
Most birds fly at relatively low altitudes of 2,000 to 5,000ft (600 to 1525m). But, of course, some species don’t even leave the ground, such as penguins and ostriches. Others stick within mere meters of the ground, rarely heading above the tree canopy.
Migrating birds are more likely to fly at high altitudes, especially if they head over mountain ranges. Birds of prey such as eagles and vultures also fly at high altitudes to help them scan huge areas for prey. Eagles regularly soar at heights of around 10,000ft, but some vultures, like the Rüppell's vulture, reach altitudes of over 35,000ft!
Only three birds can typically fly at altitudes exceeding 30,000ft+, including the Rüppell's vulture, Common crane, and Bar-Headed goose. However, several can reach heights of 20,000ft, and many more can reach heights between 10,000 to 20,000ft.
However, it’s worth mentioning that many more birds live at high altitudes. Small birds such as sparrows and hummingbirds live at approximately 16,404ft (5,000m), and they can fly easily at that altitude too.
Many birds are equipped with the adaptations required to live at high altitudes, even if just a handful are capable of continuous non-stop flight at extreme altitudes.
Bald Eagles are often spotted soaring high
Pigeons are strong and talented flyers and are capable of reaching altitudes of 6,000ft, or 1,828m. They’ve also been recorded flying at speeds of over 90mph.
Many pigeons migrate, and they’re amongst the most talented navigators of the animal kingdom, hence why they were used as an early postal system, and to send and receive messages in the World Wars.
Hawks and eagles are generally capable of high-altitude flight between 10,000 and 15,000ft. However, the Golden eagle soars to heights of over 13,000 feet (3,963 meters) when scanning for food.
While hawks and eagles fly at high altitudes, they’re not as impressive as their raptor cousins, the vultures.
Golden Eagles often fly at heights of over 13,000 feet whilst on the look out for prey
Crows are generally not high-altitude flyers. Most species of crows don’t migrate long distances, nor do they live at exceptionally high altitudes. For example, a typical American or Carrion crow will rarely fly at altitudes over 1500ft, or roughly 500m or so.
However, the crow’s close relative, the Alpine chough, is one of the highest-altitude breeding birds in the world. Alpine choughs live across many mountain ranges in Europe and Asia, including the Himalayas, where they’ve been recorded at heights of 26,500ft, or 8,000m.
Owls are not known to be high-altitude flyers, but given that some species, such as the Snowy owl are capable of long-distance migration, they may fly at reasonably high altitudes.
However, owls are generally non-migratory and probably stay relatively close to the ground.
Additionally, owls are typically nocturnal hunters and wouldn’t have much need for high-altitude flight.
Owls don't generally fly at high altitudes, but Snowy Owls are most likely to be one of the highest flying owl species
Many species of hummingbirds are imperious migrators, completing colossal journeys relative to their body size. While most hummingbirds tend to stay close to the ground, a few species have to cross mountain ranges in their path, including the Rufous hummingbird.
Some Rufous hummingbirds complete a 5,000km+ migratory trip that takes them over the Rocky Mountains!
Moreover, around ten species of hummingbirds live in the Andes at heights of over 4,500m, which is incredible considering that these tiny birds have extraordinarily fast metabolisms. Researchers discovered that these hummingbirds can survive on virtually no oxygen.
The Rüppell's vulture is the most accomplished high-altitude flier in the animal kingdom, capable of soaring to heights exceeding 37,000ft, or over 11,000m.
The Bearded vulture isn’t far behind, capable of reaching 24,000ft, or 7400m. The Andean condor is another high-altitude vulture, reaching altitudes of 21,300ft, or 6,500m, which is remarkable given its massive size. In fact, vultures make up three of the top 10 highest-flying birds.
Bearded Vultures can reach impressive heights of 24,000 feet
Most animals have a tough time at altitudes exceeding 10,000ft. Altitude sickness starts at around 8,000ft above sea level or 2,500m. At 15,000ft to 18,000ft, the oxygen content of the air is around half of what it is at sea level, making breathing difficult. While humans can operate at this altitude, they need to be acclimatized to do any serious exercise.
At altitudes of 20,000ft or higher, even most expert climbers require a regular flow of oxygen to survive. Just 200 or so climbers have completed Everest without oxygen, and many more have given up in the process.
So, how do birds manage to fly at altitudes this high? Flying is not exactly an effortless task, and you’ve got to take into account that the bird has to ascend and descend to this incredible height, often while completing a long migratory journey of thousands of miles!
Some birds have a number of specific adaptations that enable high-altitude flight. For example, they’re already acclimatized to high altitudes and have a superior hypoxic ventilatory response, enabling them to make the most of the oxygen available.
A few birds, such as the Rüppell's vulture and some hummingbirds, also possess specialized hemoglobin, a protein in their red blood cells which has a tremendous affinity for oxygen. Birds also typically have larger, more elastic lungs and can “gulp” air down their strong throats, especially in the case of geese, swans, and ducks.
Another consideration is the temperature. The temperature at 30,000ft is as low as -48F or -44.5C, which would freeze most animals to death in seconds. Birds retain heat through their feathers, but their powerful muscles also produce energy that keeps them warm.
Some hummingbirds possess a specialized hemoglobin which helps them deal with higher altitudes
There are probably just three birds that are proven to fly at heights of 30,000ft, including the Rüppell's vulture, Common crane, and Bar-Headed goose.
Eagles can fly at high altitudes of 15,000ft or so, which is much higher than a typical crow. However, the Alphie chough, also of the Corvidae family, lives and breeds at altitudes of some 26,500ft, or 8,000m!
That depends on how high the clouds are! Clouds range from low altitude varieties such as stratus and cumulus, at around <5,000ft, to cirrus and cumulonimbus, exceeding 45,000ft! The highest-flying birds, such as the Rüppell's vulture and Common crane can obtain altitudes of over 30,000ft, which puts them above most clouds.
Small single-engined planes can comfortably fly at altitudes between 10,000ft to 15,000ft, and many birds can fly at this altitude. Commercial airliners typically cruise at around 30,000 to 35,000ft, and only three species of birds can fly that high - the Rüppell's vulture, Common crane, and Bar-Headed goose. These birds have been recorded striking jet airliners. A collision between a commercial airliner and a Rüppell's vulture forced a plane to make an emergency landing in 1973.
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