The peregrine falcon (Falco peregrinus) is renowned for being the fastest bird in the world when in a dive, reaching speeds of over 200 mph. However, like all birds, peregrine falcons are unable to actually run. Their legs and feet are anatomically designed for perching and grasping prey rather than running. So while they can walk, waddle, and hop along the ground, they cannot truly run.
Anatomy of Peregrine Falcon Legs and Feet
The peregrine falcon’s legs and feet are optimized for their lifestyle as aerial hunters. Their long, powerful legs are covered in feathers down to their ankles, unlike many ground-dwelling bird species that have bare lower legs. Their toes are arranged in an anisodactyl pattern, with three toes pointed forward and one pointed back. This allows them to firmly grasp prey and perches.
Peregrine falcons have relatively large feet with long talons used for catching and killing prey. The undersides of their feet and toes are covered in small bumps called tubercles that help them get a better grip on their prey. Unlike ducks, chickens, and other ground birds, they do not have wide, flat feet well-suited for running or walking long distances.
Key Anatomical Differences from Ground Birds
There are a few key differences between peregrine falcon feet and the feet of birds that spend a lot of time running on the ground:
- No rear-facing toe – Ground birds like chickens have an extra rear-facing toe that provides stability and pushing off power when running. Peregrine falcons only have the standard anisodactyl foot pattern.
- Less robust legs – Ground bird legs are more muscular and robust for running and walking. Peregrine falcon legs are optimized for striking and grasping prey.
- Talons over toes – Peregrine falcons have large talons relative to their toes. Ground birds have smaller talons and longer toes.
These adaptations allow peregrine falcons to be agile and deadly hunters in the air but make them unable to run with any speed or endurance on the ground.
Observed Ground Speeds
While peregrine falcons are unable to truly run, they can walk, waddle, shuffle, and hop along the ground when necessary. Here are some observations of peregrine falcons moving on the ground:
- During normal walking, peregrine falcons average around 2-3 mph.
- When shuffling with wings slightly spread for balance, they may reach speeds up to 7 mph for very short bursts.
- Peregrine falcons can hop up to 3 feet vertically and 6 feet horizontally in a single bound.
- When taking off from the ground into flight, peregrine falcons can briefly sprint up to 10 mph using their wings for propulsion.
So while remarkably fast in the air, peregrine falcons are quite slow when confined to running on land. Their highest short-term ground speed is around 10 mph, less than 1/20th of their diving speed of over 200 mph.
Reasons for Relative Slowness on Land
There are a few key reasons why the peregrine falcon, despite being the fastest animal on earth in aerial dives, is so slow when traveling on foot:
Anatomical Adaptations for Flight
As discussed earlier, a peregrine falcon’s anatomy is specifically adapted for flight and aerial hunting. Their feet, legs, and overall musculoskeletal structure are not suited for running or sustained ground travel. They lack key adaptations like rear-facing toes, robust leg muscles, and stout feet that give ground birds more speed and endurance on land.
Extra Wing Weight
A peregrine falcon’s wings and associated flight muscles make up around 20% of their total body weight. This gives them exceptional flight capabilities but means they have to haul around extra weight when grounded, slowing them down. Taking flight allows them to shed this heavy wing load.
Energy Economics
It is metabolically expensive for a peregrine to run and walk compared to soaring and gliding. They have evolved to rely on gravity and air currents to travel efficiently. On the ground, their energy expenditure per unit of distance covered is much higher. As a result, they limit ground travel to preserve energy.
Lifestyle and Hunting Strategy
As aerial hunters, peregrine falcons have little selective evolutionary pressure to become faster on the ground. Their lifestyle centers on flying, perching, and diving to catch prey. Running plays little role in their hunting strategy. Other ground birds like ostriches, roadrunners, and grouse are essentially forced to become good runners to survive predation pressure.
Comparison to Other Bird Species
While slow compared to specialized running birds, the peregrine falcon can cover ground faster than many of its relatives:
Vs. Other Falcon Species
- Gyrfalcon: top speed around 5 mph
- Kestrel: top speed less than 2 mph
- Merlin: estimated 3-4 mph top speed
So the peregrine is perhaps the speediest falcon on foot even though it’s no roadrunner. Its shorter wings and larger feet contribute to its greater agility on the ground compared to close relatives.
Vs. Other Bird Groups
| Bird Group | Top Ground Speed |
|---|---|
| Ostrich | 43 mph |
| Emu | 31 mph |
| Roadrunner | 20 mph |
| Pheasant | 11 mph |
| Peregrine Falcon | 10 mph |
| Mallard Duck | 8 mph |
| Chicken | 9 mph |
| Turkey | 25 mph |
| Mourning Dove | 15 mph |
So while peregrine falcons are faster on foot than many bird groups like ducks, doves, and fellow raptors, they are much slower than specialized running birds like ostriches and roadrunners. The peregrine’s skills lie in the sky rather than on the ground.
Factors That Temporarily Increase Speed
Under certain conditions, peregrine falcons can exceed their normal observed walking and shuffling speeds of 2-7 mph:
Downhill
On moderately steep inclines, peregrine falcons may be able to reach 15 mph using gravity assistance before opening their wings and transitioning to flight.
With the Wind
A strong tailwind could boost a running/hopping peregrine to speeds over 10 mph for very brief spurts.
Predator Panic
In a life or death situation, peregrine falcons will run/flop at their absolute maximum speed to try and take flight. Adrenaline could provide temporary burst speed of up to 15 mph.
After Landing
Peregrines can utilize remaining airspeed for a few brief seconds after landing from a stoop or long flight to rapidly run/waddle before coming to a full stop.
However, these special situations only allow the falcon to exceed typical observed speeds for a few seconds at most. Their anatomy remains fundamentally constrained compared to ground bird specialists.
Conclusion
In summary, while renowned for aerial speeds over 200 mph, peregrine falcons have significant anatomical and evolutionary constraints that prevent any real running ability on the ground. At best, they can only manage 10-15 mph in short bursts and average walking/hopping speeds of just 2-7 mph. Their skillset is highly specialized for hunting other birds midair. While they can move faster than some related raptor species afoot, they are vastly outpaced by ground bird groups like ostriches and roadrunners that are adapted for running down prey. So next time you see a peregrine falcon take flight, appreciate that it is leaving the earthly bonds of gravity rather than the need for speed afoot!
