If you’ve ever looked up at the sky on a partly cloudy day, you may have wondered: do birds fly above the clouds? This is a fascinating question that many curious minds want the answer to. Keep reading to learn everything you need to know about whether our feathered friends take flight into the clouds.
If you’re short on time, here’s a quick answer to your question: Yes, birds do fly above clouds under certain conditions. Most birds cannot fly above very high clouds due to lack of oxygen, extreme cold temperatures, and other hazards. But many species routinely fly over low-lying clouds.
Now, let’s dive into the details…
Altitude Limits for Bird Flight
Oxygen Availability
As birds fly higher, the air becomes thinner and oxygen levels decrease. This limits the maximum altitude most birds can reach. The bar-headed goose is one amazing exception – it can fly over the Himalayas at altitudes up to 30,000 feet where oxygen levels are only 30% of those at sea level!
For most birds, oxygen starvation sets an altitude limit around 20,000 feet. Their efficient respiratory systems allow more oxygen uptake than humans, but even they cannot extract enough oxygen above this height.
Temperature
Temperatures also drop significantly at higher altitudes. While birds generate body heat through metabolism when flying, the extreme cold places physiological limits. Small birds lose heat quickly with their high surface area to volume ratio.
Larger birds like swans and geese can migrate at up to 29,000 feet elevation, but most songbirds and smaller birds fly lower where temperatures are warmer.
Other Environmental Factors
High winds, air pressure changes, humidity, and other weather events also influence how high birds can fly. Storms and headwinds force many birds to fly lower or seek shelter. However, when aided by tailwinds, some migrating birds can reach exceptional altitudes.
Bar-headed geese have been recorded as high as 37,000 feet above sea level! Additionally, different species have adapted to their own altitude niches based on factors like wing shape, heart and lung capacity, and hemoglobin levels in blood.
Evidence That Birds Fly Above Clouds
Direct Observations
There is substantial evidence from direct observations that birds do indeed fly above clouds. Pilots and passengers on airplanes frequently spot birds soaring at altitudes of over 30,000 feet, well above even the highest clouds.
Scientists have also directly observed migrating birds flying over clouds during research flights. For example, a 2018 study tracked 48 birds flying over cumulus clouds during fall migration over the Great Lakes region in the central United States.
The birds were flying at altitudes between 4,500 and 6,800 meters (14,700 to 22,300 feet).
Migration Tracking
In recent decades, scientists have also gathered extensive evidence that birds fly above clouds through migration tracking studies. By attaching lightweight radio transmitters to birds, researchers can track their migration routes via satellite, following them as they fly thousands of miles between breeding and wintering grounds.
Data from bar-headed geese, which migrate over the Himalayas, show that these birds regularly reach altitudes over 24,000 feet during migration, soaring well above the mountaintops and any clouds. Similar high-altitude migration has been recorded in shorebirds, raptors, songbirds, and more.
Anecdotal Accounts
There is also a long history of anecdotal sightings of birds flying above clouds. Accounts from pilots, sailors, mountaineers, and other observers published over the past 300 years contain repeated references to spotting birds hundreds or thousands of feet above cloud layers.
While not scientifically rigorous evidence, these accounts help confirm that birds do indeed fly at great heights above clouds during migration and regular flights. Some species like vultures and condors are especially known to utilize air currents to soar to extreme elevations far above where any clouds could form.
Which Birds Fly Highest Above Clouds
Vultures
Vultures are well known for their ability to soar to great heights. Their large wingspans, up to 7 feet across, allow them to ride thermal updrafts and ascend to altitudes of over 20,000 feet. Some species, like the Andean condor, have been recorded soaring at heights above 30,000 feet where the air is thin and temperatures are below freezing.
Vultures have special adaptations like efficient lung design and hemoglobin that allow them to thrive in the upper atmosphere. While cruising at high elevations, vultures use their incredible eyesight to scan the landscape below for carrion.
Once spotted, they can gracefully descend from their lofty perches to feed.
Geese and Swans
Many geese and swans are capable of reaching impressive heights during migration. Species like the bar-headed goose regularly pass over the Himalayas at altitudes above 20,000 feet. The demands of their biannual migratory journeys force geese and swans to adapt to flying and breathing effectively in oxygen-depleted air.
Additionally, their V-shaped flight formation serves as an aerodynamic strategy that conserves energy. The lead bird in the flock splits the air resistance, creating an updraft that makes it easier for the trailing birds to fly. When the leader tires, another goose rotates into the front position.
This cooperative formation allows geese and swans to efficiently travel thousands of miles and fly over mountains higher than even the most ambitious mountaineers ascend.
Eagles
Eagles are aerial masters capable of rising far above the landscape below. Golden eagles and bald eagles frequently soar at 10,000 feet or higher using thermal updrafts to gain loft and survey their territory.
However, eagles do not maintain the extreme high-altitude abilities of vultures and geese during migration. The highest recorded eagle sighting was a bald eagle spotted at an elevation of 20,700 feet in California’s Sierra Nevada mountains.
While eagles may occasionally reach heights over 20,000 feet, most flights occur between a few hundred to several thousand feet in elevation. At these heights, eagles can effectively spot and hunt prey while avoiding the thin, frigid air of higher altitudes.
Low Cloud vs High Cloud Flight
Cumulus and Stratus Clouds
Birds generally do not fly above low-altitude clouds like cumulus and stratus clouds. These clouds form in the lower atmosphere at altitudes between ground level and 6,500 feet. With towering vertical development, cumulus clouds can reach over 39,000 feet in the summertime.
However, most cumulus clouds are much lower and birds can easily fly above them.
In contrast, stratus clouds blanket the sky in flat, uniform layers. Forming closest to the ground, they rarely exceed 6,500 feet in elevation. While not an obstacle for most birds, stratus clouds do affect visibility for avian navigation and feeding.
Thick fog is an example of extremely low stratus cloud cover.
Altostratus, Altocumulus and Cirrocumulus Clouds
Mid-level cloud layers called altostratus, altocumulus, and cirrocumulus occur at altitudes too high for most bird species. These types of clouds take shape between 6,500 to 25,000 feet in the air. Some migratory birds can ascend heights to clear small mid-level clouds.
However, the oxygen is too thin for prolonged flight above 20,000 feet elevation.
For example, the bar-headed goose is renowned for extreme high-altitude migration over the Himalayan mountain range. At heights exceeding 20,000 feet, it navigates icy terrain and towering cumulonimbus storm clouds.
Cirrus Clouds
Wispy cirrus clouds represent the highest cloud formation, drifting along above 25,000 feet in altitude. No birds can fly over or through the ice crystal composition of cirrus clouds. However, some unique migratory species can climb astonishingly close to the elevation of high cirrus cloud cover.
For example, Whooper swans have recorded flights reaching 29,000 feet up in the atmosphere. Yet even these lofty heights do not surpass the upper limits of cirrus clouds. So while select avian species demonstrate incredible feats of high-altitude endurance flight, cirrus clouds continue to mark the upper boundaries for this rarified airspace.
Conclusion
As we have seen, whether birds fly above the clouds depends on the type of cloud and its altitude. Most bird species are capable of flying above low-lying clouds like cumulus and stratus when the need arises.
But very few can ascend above high-altitude cirrus clouds over 20,000 feet, due to physiological limits. While the sky may seem limitless to us on the ground, even the most accomplished aviators in the animal kingdom have their boundaries.
The next time you spot birds disappearing into the clouds, take a moment to appreciate the remarkable heights they can achieve under the right conditions.
