Griffon vultures are large birds of prey that are known for their ability to soar at extreme heights. These vultures are found across southern Europe, Asia, and northern Africa and are distinguished by their pale plumage and long, broad wings. One of the most remarkable things about Griffon vultures is their tendency to fly at altitudes of over 20,000 feet, far higher than most birds venture. But why do Griffon vultures fly so high in the sky? There are several key reasons these birds take to the heights.
To Take Advantage of Thermals
One of the main reasons Griffon vultures fly high is to take advantage of rising warm air currents known as thermals. Thermals form when sunlight strikes the ground and warms the air above it. This warm air then begins to rise in columns in the atmosphere. For vultures and other large soaring birds, thermals act like elevators, allowing them to ascend to great heights with little effort. By riding thermals, vultures can gain altitude and soar for long distances with minimal energy expenditure. This is crucial for such large birds. Vultures have high wing loading, meaning their wings are relatively short and broad compared to their body weight. This makes prolonged flapping flight energetically taxing. Instead, vultures rely heavily on soaring and gliding. By catching thermals and deftly maneuvering their long, broad wings, Griffon vultures can efficiently ride the rising air currents up to 20,000 feet or more.
To Survey Wide Territories for Food
Another key reason Griffon vultures fly high is that it allows them to survey vast swaths of land for food resources, specifically carrion. With their acute eyesight, vultures soaring at 20,000 feet are able to scan the ground for miles in every direction, searching for animal carcasses. The higher a vulture flies, the more terrain it can search for potential food sources. This is highly advantageous as Griffon vultures feed exclusively on carrion and finding animal remains scattered across the landscape can be challenging. By soaring at great heights, the vultures can methodically quarter the land, increasing their chances of detecting a meal. Once a carcass is spotted, the vulture can then swiftly glide down to feed. Their ability to find food sources is further enhanced by their tendency to roost and breed on cliffs, which provide excellent vantage points above the surrounding land.
To Avoid Predators and Competition
Soaring at extreme altitudes helps keep Griffon vultures safe from terrestrial predators like foxes, wolves, and jackals. It also reduces competition from smaller raptors or scavenging mammals that may try to chase vultures from carcasses. Large birds gliding 20,000 feet up are well out of reach from threats on the ground. At these heights, Griffon vultures are essentially inaccessible to most competing scavengers. The only real competition comes from other huge soaring birds, like cinereous vultures, which also exploit thermals to fly high and search widely for carrion. By partitioning the sky, different species of vulture are able to coexist. Griffon vultures focus on the highest levels, staying above the ranges where smaller raptors hunt for live prey.
Unique Adaptations for Extreme Altitude
Griffon vultures possess a number of specialized adaptations to facilitate their incredible high-altitude soaring:
Large Size and Broad Wings
As mentioned earlier, the sheer size and proportions of Griffon vultures provide a morphological basis for their ability to fly extraordinarily high. Their wingspans can reach over 9 feet and their bodies can weigh 15-25 pounds. Compared to other birds of this size, the vultures’ wings are exceptionally long and broad. This high wing loading allows the vultures to soar very efficiently once aloft, but means they rely heavily on thermals and updrafts to gain altitude. By skillfully maneuvering their large wings, Griffon vultures adeptly catch rising warm air and ascend to heights few birds can reach.
Efficient Respiration
Soaring for hours at 20,000+ feet requires an efficient respiratory system that can extract adequate oxygen at high altitudes where air density is low. Griffon vultures have adaptations like relatively small lungs and a specialized system of air sacs that facilitate oxygen exchange during respiration. Extra capillaries in the birds’ lungs also help improve gas exchange. Their streamlined body shape further enhances their aerodynamic efficiency during flight.
Tough Against Low Temperatures
The air temperatures experienced by Griffon vultures on their high-altitude flights can drop below freezing. Special adaptations like compact body feathers, thick downy underlayers, and thermal windows in their wings help minimize heat loss during long exposure to the cold heights. The bare skin on their heads and necks is also vital for thermoregulation, allowing the birds to vent excess heat that builds up while soaring.
Keen Long-Distance Vision
To be able to spot food sources from 20,000+ feet, Griffon vultures have incredible vision. Their eyes are specially adapted to detect subtle movement on the ground from great distances. A highly-developed fovea or region of the retina provides visual acuity, while an additional transparent eyelid protects their eyes at high speeds and altitudes. Griffon vultures have some of the sharpest vision of all raptors, enabling them to scan vast landscapes for carrion.
Typical Flight Profile
A typical high-altitude flight for a Griffon vulture proceeds as follows:
Taking Off From a Clifftop Perch
Griffon vultures frequently nest and roost on cliffsides, ideally positioned to catch rising morning thermals. After warming and drying its wings while facing into the sun, the vulture will drop from its precipice perch and swoop downward to gain speed and lift. With a few powerful thrusts from its broad wings, it reaches an airspeed fast enough to start soaring upward.
Catching a Thermal
As the Griffon vulture nears the upward rushing column of warm air, it will extend its wings to their full span, delicately adjusting the long flight feathers to maneuver into the thermal. With wings held stiffly, the vulture circles tightly within the rising column, quickly gaining several hundred or thousand feet of elevation.
Repeating to Reach Maximum Height
As it approaches the top of one thermal, the vulture will gently bank and glide toward the next thermal it has spotted, repeating the process of swooping and circling to ascend. It may catch ride after ride on successive thermals until it reaches heights of 10,000 to 20,000 feet or more.
Cruising and Scanning for Food
Once it reaches maximum altitude, the Griffon vulture will cruise back and forth in search of food, utilzing its keen vision to scan the terrain below. Its widespread, stereoscopic vision allows it to search wide swaths of land from side to side.
Spotting Food and Descending
When the vulture finally spots the dark, distinct shape of a carcass on the ground, it halts its circling and enters a swift stooping dive with wings tucked. It may descend several thousand feet in seconds before swooping low over the carrion, scattering any competitors in preparation to feed.
Rising Upward Again
After feeding, the sated vulture takes advantage of thermals and updrafts to launch itself skyward once more, coasting upward to resume scanning the landscape. It repeats its orbiting ascent until it reaches a preferred soaring altitude where it can continue surveying the land for more feeding opportunities.
Differences From Other Birds of Prey
Griffon vultures have different flight capabilities and behavioral patterns than other types of large raptors due to the vultures’ unique adaptations and diet:
Soaring vs Flapping
While eagles, hawks, and falcons rely extensively on flapping flight to power their flight, Griffon vultures soar on air currents and thermals to cover huge distances with minimal wing flapping. Flapping flight is more energetically costly.
Scavenging vs Hunting
Vultures like Griffon vultures utilize high altitudes to visually locate carrion to scavenge. In contrast, hunting raptors like golden eagles employ high soaring to survey the ground for live prey like rabbits and marmots.
Group vs Solo
Griffon vultures will congregate at carcasses and exploit thermals together. Other solitary raptors like ospreys hunt and fly alone outside breeding season.
Soaring Hours vs Perching
Vultures spend hours riding thermals versus shorter bouts of active flight and perching for hunting raptors. Eagles can also soar at altitude but alternate with low flights and perches.
Range of Flight
Vultures travel more extensively from steep cliffs and high perches versus smaller raptors defending distinct nesting territories with aerial displays.
So while other large raptors take advantage of some soaring, Griffon vultures are uniquely specialized for exploiting high altitude thermals to locate widely dispersed food.
Benefits of Being a High Flier
The vulture’s ability to fly at extreme altitudes confers a number of advantages:
Minimizes Energy Expenditure
Soaring at altitude allows the Griffon vulture to search enormous areas while expending minimal energy. Flapping flight is far more demanding.
Improves Search Efficiency
Excellent visibility from great heights enables vultures to quickly locate sparsely distributed carrion critical to their diet.
Access to Less Competition
By partitioning the sky, high-flying vultures avoid competition for carcasses with terrestrial scavengers.
Safety From Predators
Soaring at 20,000 feet keeps the vultures and their eggs/chicks in cliff nests safe from ground predators.
Ability to Move Long Distances
Riding high-altitude thermals and updrafts allows vultures to easily travel 100 miles or more per day with minimal effort.
Scope of Huge Territories
High flights facilitate surveying vast home ranges of over 155 square miles in search of widely dispersed carcasses.
In essence, soaring high provides Griffon vultures with a highly efficient and effective means of locating scarce food sources across broad areas while expending minimal time and energy doing so. These advantages appear to maximize the vultures’ fitness and reproductive success.
Threats Facing Griffon Vultures
While well adapted for high-altitude scavenging, Griffon vultures face a number of conservation threats today:
Habitat Loss
Development, agriculture, and overgrazing degrade cliff nesting sites and reduce food availability.
Poisoning
Consuming poisoned carcasses leads to high mortality. Poisons are used to control carnivores and rodents.
Electrocution
Collision with power lines and electrocution on pylons kills many vultures. Their large wingspans increase risk.
Declining Food Sources
Modernization of livestock practices means fewer livestock carcasses available to vultures.
Human Disturbance
Increasing proximity of human activities near nesting colonies leads to disturbance and abandonment.
Illegal Shooting
Some vultures are still subject to direct persecution. Farmers may falsely believe vultures spread disease.
Targeted conservation programs aim to reduce these threats and protect remaining Griffon vulture populations. Efforts include supplementary feeding, nest guarding, and adding safe perching and nesting platforms on pylons. But preserving sufficient high-quality habitat remains key to safeguarding the vultures’ iconic high-flying lifestyles.
Conclusion
In summary, Griffon vultures are highly specialized to fly at extreme altitudes in order to locate carrion across vast landscapes. Their large size, broad wings, keen eyesight and other adaptations facilitate exploiting high-altitude thermals to search territory efficiently with minimal energy expenditure. Soaring at heights up to and above 20,000 feet allows Griffon vultures to find food while avoiding threats from predators or competition. While facing substantial conservation challenges today, these magnificent high fliers continue their vital ecological role as scavengers thanks to the flight capabilities that grant them access to an aerie three miles above the ground.
