The Peregrine Falcon

All about the fastest creature on the planet.

December 5, 2020
Ivan Phillipsen

Key Features

If you’ve seen a Peregrine a time or two, you probably have a mental picture of this bird’s crisp silhouette. Zipping through the sky overhead, you see a medium-sized raptor with elegant wings (watch). These taper to sharp points. The bird’s wing beats are deep and fluid. Its tail is on the long-ish side. Seeing this shape alone may be enough for you to identify a Peregrine Falcon.

This bird is roughly the size of a crow. Female Peregrine Falcons are bigger than males. Falcons along with other birds of prey generally show this kind of size difference between the sexes. This is a kind of sexual dimorphism. In most other types of birds, the male is the larger sex.

Our falcon’s wings, as I mentioned, taper to a neat point. The sickle shape of the wings make them superbly-adapted for fast flight and aerial agility. We see a similar wing shape in swallows, swifts, plovers, and other speedy fliers. Peregrine’s routinely zoom around at 30-50 miles per hour, which is 48-80 kilometers per hour. That’s when they’re not even really trying to go fast.

There’s a fair amount of variation in plumage colors and patterns across the world’s Peregrine Falcon populations. But the standard model comes with a slaty blue-gray upper side with a white to buff underside. There are usually fine, dark bars or spots on the breast and belly as well.

Diving Peregrine Falcon (Falco peregrinus), showing the pointed, swept-back wing shape.  Photo by Dennis Jacobsen.

The head and facial markings of this bird are pretty striking. It looks like it’s wearing a dark gray helmet. Like those ancient Greek helmets with metal plates that protect the cheeks. Or like a gladiator’s helmet.

There are dark feathers on the crown that extend around the eye and downward to the chin. The part below the eye is called a malar stripe. In some populations these markings are narrow and stripe-like, in other populations they spread out to cover the whole cheek.

One hypothesis is that these malar stripes work the same way as the ‘eye black’ grease used by football players, baseball players, and other sportspeople. Eye black supposedly reduces glare from the sun. But it seems there isn’t very strong scientific evidence to support this—in athletes, or falcons, or cheetahs, for that matter, which also have markings like this.

The keen eyes of a Peregrine Falcon are large and, dare I say, expressive. They’re a rich brown color and are surrounded by contrasting yellow eyelids and facial skin.

Headshot of a Peregrine, showing several features discussed in the episode: the malar stripe, the tomial tooth, and tubercle of the nostril. Photo by Peter Neu.

The upper part of the beak is sharply hooked, as you would expect for a raptor. But if you look closely at it you’ll notice a special bonus feature. Near the tip, there’s what looks like a little fang on either side. This is called a tomial tooth. The word tomial comes from the technical name for the cutting edge of a bird’s beak: the tomium. There’s a corresponding notch on the lower bill that the tomial tooth slots into when the bill is closed.

Now, this isn’t an actual tooth, like what you have in your mouth. No living bird has that kind of teeth. The tomial tooth is just a specialized protrusion of the upper beak’s keratin sheath. All falcons have tomial teeth. We’ll talk about what they’re used for in just a bit.

As for other key features of the Peregrine Falcon… the way it catches its prey is high on the list of things that make you go “wow!” If there’s one thing most people know about this bird it’s this: the Peregrine Falcon is the fastest animal on the planet.

This falcon eats other birds. That’s its thing. And to catch birds in the air you need to be fast and you need to be maneuverable. Peregrines are both. We’ll come back in a few minutes to look at the details of how these falcons hunt.

Evolution and Diversity

Peregrines are in the family Falconidae. This family includes about 65 species of falcons, kestrels, and caracaras. Many bird field guides are organized taxonomically, with more primitive/ancient bird families in the beginning and more recently-evolved birds toward the end. Back in the day—actually not that long ago—field guides showed falcons right next to other diurnal birds of prey like hawks and eagles.

But it turns out that falcons are not closely related to hawks and eagles. They are much more closely related to, believe it or not, parrots. Yes, parrots. Sure enough my Second Edition copy of Sibley Birds West here, published in 2016, has woodpeckers, then falcons, then parrots. Falcons are nowhere near hawks and eagles.

This reconfiguration was spurred by a series of studies published between 2006 and 2014. They used genetic data from DNA to investigate the evolutionary relationships among the world’s bird families. The results of those studies gave us an improved understanding of which birds are related to which.

Avian taxonomy at the family level is an active area of research and more rearrangements are probably in our future. But it’s pretty clear that falcons and hawks are not even cousins. These birds look similar mostly because natural selection has honed them over millions of years, making them into better killing machines. These two, unrelated families have evolved independently to share some adaptations for living as feathered predators. So this is a lovely example of convergent evolution. Two unrelated organisms have ended up with similar features because they face similar pressures under natural selection.

Okay, let’s get back to looking at just the one species, our Peregrine Falcon. This bird lives all across the world, right? It’s no surprise, then, that it shows some geographic variation in appearance across its vast range. Over the years, an insane number of subspecies have been named for the Peregrine Falcon—about 75 all told. But most of them have now been “canceled” and we’re left with about 19 accepted subspecies. That’s still a lot! Among these subspecies we have South American, Tundra, Mediterranean, African, Australian, and so on. The subspecies have distinct, but sometimes subtle, plumage colorations that set them apart. Some are more pale, some sport more reddish hues, some have different patterns of barring on their bellies, and so on.

Several studies, published between 2006 and 2018, used genetic data from DNA to look at the evolutionary relationships among the Peregrine Falcon subspecies. The results of these studies showed that there are genetic differences between at least some of the subspecies. But the differences aren’t huge. The most likely explanation for the low level of subspecies distinctiveness at the genetic level is that the Peregrine Falcon has only recently spread across the world, probably since the end of the last Ice Age about 10,000 years ago. Evolutionarily, that’s not very much time at all. Not enough time for Peregrine populations living in different parts of the world to accumulate a bunch of genetic differences. Perhaps by using higher resolution genetic data, like whole genome sequences, biologists will eventually detect more genetic differences between these subspecies.

Distribution and Habitat

When talking about the geographic range of the Peregrine Falcon, we shouldn’t ask ‘where does it live?’ The question should be ‘where doesn’t it live?’ A handful of bird species are said to be “cosmopolitan.” in this context means “found all over the world.” The Peregrine Falcon is the perfect example of a cosmopolitan species. In fact, no other bird has a wider range than the Peregrine. And, it’s perfectly named; the name Peregrine comes from the Latin word for foreigner or traveler.

So where else doesn’t the Peregrine Falcon live? There are some big gaps in its distribution. It doesn’t live in the vast grasslands of North America or Central Asia. Nor does it live in the Sahara Desert, the Amazon Basin, or the glaciated interior of Greenland

Now dig this: even though these falcons live in far-flung places like Fiji and they’ve started showing up on the even more isolated islands of Hawaii, they aren’t found in New Zealand. How weird is that? New Zealand has its own species, New Zealand Falcon (Falco novaeseelandiae). Maybe Peregrines haven’t been able to get a foothold because they’ve been chased off by the native falcons? But, if that’s the case, you’d think someone would have at least seen a Peregrine Falcon in New Zealand by now.

If these birds can fly all the way to Hawaii, they are certainly capable of getting to New Zealand. But as far as I know, this species has never been reported there. This is a biogeographic mystery that we need to solve!

Anyway, we can say that this falcon is wide-ranging—like, the widest ranging bird of prey. But within its range, individuals or breeding pairs are sparsely distributed. You won’t find them in high density. There aren’t great flocks of Peregrine Falcons swooping around anywhere.

It’s hard to say why this species has been so successful in spreading across most of the world. Maybe it’s because it eats birds, and birds are friggin’ everywhere. Who knows?

It’s easier to hypothesize about the underlying cause of the Peregrine's sparseness in the landscape. For one, it’s a top level predator. We know from the basic principles of ecology that there are always fewer predators than prey. Maybe you’ve seen the classic food pyramid with plants on the bottom row, primary herbivores above them, and so on up to the tippy top of the pyramid whereupon you will find the apex predators. Such a beast is the Peregrine Falcon.

Another possible reason these birds are few and far between across the land is their need for certain habitats. At least where they breed, Peregrine Falcons need high cliffs to place their nests. Some surveys have shown that nest sites tend to be spaced about 3.5 miles or 5.5 kilometers apart. Peregrines are territorial in the breeding season and don’t tolerate trespassers that get too close to their cliff

Speaking of habitats… This species, with its vast range, can be found in a whole bunch of different habitats: Tundra, desert, wetlands, coastlines, mountains, and more. But wherever they breed, they need cliffs. Or at least cliff-like structures, such as skyscrapers or bridges.

The feature common to all Peregrine Falcon habitats, whether in the breeding season or not, is a lot of open air space. These falcons don’t like any obstructions like dense forest to get between them and their avian “meals on wings.” They need to be able to see their prey and pursue them over great distances.

Diet and Foraging

You know that the diet of the Peregrine Falcon is mostly birds. Between 77 and 99% of all the prey critters eaten by Peregrines are birds. On the menu are many birds that are smaller than a crow, like songbirds, and some that are bigger than a crow, like small geese. Crows themselves, which happen to be exactly as big as a crow, are also eaten. And this means, of course, that Peregrines sometimes chow down on birds that are larger than themselves.

Across the world, Peregrine Falcons terrorize 1,500 to 2,000 bird species. That’s up to about 10% of all bird species on Earth! They’ve been recorded preying on at least 429 bird species in North America alone. So these falcons aren’t terribly picky eaters.

There are regions where Peregrine Falcons are more specialized in their food choices. Up and down the Pacific Coast of North America, for example, more than 75% of the birds they eat are seabirds in the auk, storm-petrel, and shearwater families. Puffins are in the auk family. So for those adorable puffins that we all love, the Peregrine Falcon is the stuff of nightmares.

Besides birds, the next most frequent victims of this falcon are bats. In places like Texas and Brazil, Peregrines catch bats at sunset. They sometimes eat bats while flying. In one example, a falcon in the Grand Canyon ate 7 bats in 20 minutes—without ever landing!

Okay, now I’m going to lay out how a Peregrine Falcon typically hunts and kills birds. The basic stages are search, pursuit, capture, killing, and eating.

Searching for prey usually takes place from a perch on a high vantage point. Cliffs are the best. Like other raptors, the Peregrine Falcon has superb vision. They can see with much higher resolution than we can, in both space and time. By that, I mean they can see finer details at all distances and that they can see motions that would just look like a blur to you and me. I did a blog on the vision of birds, so check that out if you’d like to learn more about this.

Having spotted a juicy-looking bird, our falcon takes off. If the prey bird is flying below, the falcon may drop into a dive right away. But if the prey bird is up high, the falcon will often take a spiraling path upward to get well above it. This is called “towering up” or “ringing up.” I should point out that there are some special terms like these that come from the world of falconry.

Peregrine Falcons have several modes of pursuit. They can come up from below to hit their prey, they can chase directly from behind, they can sort of sneak up by flying low over the terrain, etc.

But their most famous method of operation, and the one we’ll discuss here, is the “stoop.” Stoop is another special word that means a diving attack behavior where the bird tucks in its wings.

Once zeroed in on the prey bird from high above, our falcon begins its dive, its stoop. In the first phase, it pulls its wings in tight against its body. The bird now takes on a streamlined, teardrop shape. Drag is reduced to a minimum as the falcon elongates its body, getting even more streamlined as it plummets downward, faster and faster.

So here we have the fastest animal on Earth, moving at its maximum speed. You’ve probably heard that a Peregrine can get up to 200 miles per hour. That’s 320 kilometers per hour. Just a couple years ago, one falcon was clocked at 242 miles per hour, which is 389 kilometers per hour. Amazing!

How was this world record achievement measured? Well, a guy named Ken Franklin raised a female Peregrine named Frightful. That’s a great name. Ken was a skydiver and he trained Frightful to chase him as he leaped out of planes and plummeted to the Earth. One day, the two of them started a dive from 17,000 feet. Moments later Frightful was clocked at 242 miles per hour.

What an incredible experience that would be, huh? To match speeds and freefall side-by-side with a Peregrine Falcon, who also happened to be your little buddy?

One physiological challenge for the falcon when moving at this speed is air pressure in its lungs. If air could freely enter the nostrils, the force of it might cause damage to the respiratory system or keep the falcon from breathing. But—natural selection to the rescue! The nostrils of Peregrines have a cool little adaptation called a tubercle. The tubercle is a nugget of hard tissue just inside the nostril opening which slows down the inrushing air. Problem solved.

Getting closer to its prey now, the falcon changes its shape by moving its wings slightly outward from its body. This forms a sort of ‘M’ shape. Now we're at the second phase of the stoop. The change in posture causes some deceleration, but the falcon is still moving plenty fast. What it gives up in speed, it seems to gain in maneuverability.

Some recent studies involving computer simulations combined with field observations suggest that the Peregrine’s high speed and wing posture work together at this stage to create the ideal aerodynamic conditions. This gives the falcon a high level of maneuverability, which it needs in order to make lightning-quick course corrections as it closes in on its prey.

Okay, our falcon is now within just a few meters of its target prey. This is the final stage of the stoop. Most often, this is when the falcon spreads its wings and pulls out of the dive at the last moment. It shoots its feet forward and grabs onto the other bird with its long claws.

Less frequently, a Peregrine won’t really pull out of the dive—it will just smash into its prey like a meteor. Bam! Either way, there’s usually an explosion of feathers. And you can guess whose feathers they are.

If the falcon misses its target or hits it without grabbing hold, the predator can swoop around to strike again. Or snatch a stunned bird that's now tumbling to the ground.

If the falcon does the whole meteor smash thing, its prey might be killed instantly on impact. This strike is still made with the feet. It was once thought that the falcon balled its toes into a sort of fist to deliver this killing blow. But there seems to be some uncertainty about that.

In the more common situation where the falcon just grabs the other bird with its feet, death comes in another way. And it’s not from the claws themselves. Some other raptors kill by piercing their prey with their long talons.

The Peregrine Falcon uses another pointy weapon: its tomial tooth. Well, its tomial teeth, rather—both of them. While still in flight or after landing, the falcon bites into the back of its victim's neck. The tomial teeth are used to separate the cervical vertebrae and sever the spinal cord.

Our falcon, victorious, carries its freshly killed prey to a perch or, if the prey is too large, to the ground. There, the falcon plucks feathers from the dead bird.

The final stage, eating, begins with the falcon ripping the head off of its meal. Gruesome, yes, but when you think about it, it’s not really worse than some of the ways humans eat. I’m thinking about what we do to lobsters. And many people eat monkey brains, fish eyeballs, and stuff like that. So maybe we shouldn’t judge the falcon.

Having all or part of its victim’s head, the falcon keeps gorging until it's satisfied. It will survive to hunt another day.

A wide range of hunting success rates have been reported for Peregrine Falcons around the world. Some individuals make successful kills on more than 90% of their attempts. Others have it much harder, being successful less than 10% of the time.

Even when a Peregrine makes a kill, it might have to fend off a pesky kleptoparasite. Remember that a kleptoparasite is an animal that steals food from another animal. Birds that steal from Peregrine Falcons include Bald Eagles, Golden Eagles, Rough-legged and Red-tailed Hawks, Gyrfalcons, Ravens, gulls or various flavors, and more.


If you look at the global range map of the Peregrine Falcon—in a field guide or online—you’ll see that there are many places where these birds live year-round, where they’re more or less residents. But other regions are occupied by Peregrines in only the breeding season. And still other regions serve as their home in only the non-breeding season.

The point here is that: some Peregrines are highly migratory; others stay in the same place all year. Most of the migrants are birds that breed in the boreal or arctic regions in the northern summer. They make long journeys south for the winter. Birds that breed in the far northern tundra of Alaska, for example, might fly all the way to Chile or Argentina. Their journeys—their peregrinations, if you will—can be almost 9,000 miles or 14,500 kilometers, one way.

But even birds that breed at high latitudes sometimes stay put year round. Some Peregrine Falcons living in Alaska’s Aleutian Islands are residents. Even though it’s super dark and cold up there in the winter, there are still greasy seabirds to snack on. This plentiful food supply is apparently why the falcons can just stay put.

Now, if you spot a Peregrine in the southern hemisphere, that bird is either a year-round resident or a migrant visiting from far to the north. There isn’t an upside-down migration situation where Peregrines breed in southerly regions like Argentina or Australia and then fly north to spend the non-breeding season in Alaska, Russia, or wherever.


When it comes to breeding, Peregrine Falcons are monogamous. The female and male stay together through the breeding season but usually do their own thing in the non-breeding season. The pair will reunite when they return to their nest site the next year.

To reinforce their pair bond each spring, these birds have an assortment of courtship behaviors. For example, they make special calls to each other. And they display to each other, in several ways, including flashy aerial performances complete with loop-de-loops, barrel rolls, zig zags, and figure eights. Most often it’s the male who does all this.

The nest of the Peregrine Falcon is, well, not what you might be picturing. These birds don’t build a nest out of any material. They just find a sweet spot on a lofty cliff, like a ledge or alcove, and then scrape around in the dirt and call it good. This type of nest is actually, technically, called a scrape. When Peregrines find a nest site, they often show strong fidelity in returning to it every year. For an extreme example, there’s some evidence from a site in Australia that generations of falcons have been using the same nest site for at least 16,000 years. Think about that… 16,000 years.

Having reestablished their bond, a pair of Peregrines mate and then pop out a few eggs. Both parents help raise the babies. On average 1 or 2 young falcons will survive to leave the nest.

While occupying their nest cliff, the adult falcons are highly territorial. If another Peregrine comes lurking around the eyrie, the territory owners will attack. Fighting falcons grab each other with their talons and bite each other's head and neck. These gnarly brawls can last for hours and can result in one bird being killed.

Eagles, hawks, owls, and gyrfalcons are predators of Peregrines, especially the chicks. So if one of these predators tresspasses on a Peregrine’s territory it’s often seen as a threat. There are cases where threatened Peregrines have straight up murdered much larger birds. For example, in more than one incident a Bald Eagle has been bashed in the head and killed by a Peregrine Falcon.


The conservation story of the Peregrine Falcon is long and dramatic. I’ll just give you a rough sketch of it here as we wrap up our look at this wonderful raptor.

In the bad old days, before birds received any legal protection, Peregrine Falcons were sometimes shot by people who saw them as a threat. These jerks were often gamekeepers who didn’t want the falcons to eat their pheasants or grouse.

Another group that has persecuted Peregrines is Pigeon fanciers. Pigeon fanciers shoot or poison falcons to protect their inbred racing pigeons or whatever.

And despite major laws now protecting these birds, this sort of thing is still going on. For example, the biggest threat to Peregrines in the UK today is illegal persecution, from gamekeepers and pigeon fanciers.

Between the 1940s and 1970s the enthusiastic use of the pesticide DDT around the world became an existential threat to Peregrine Falcons and numerous other birds. DDT and its metabolic residues accumulate in animal tissues. They become more concentrated as they move through the food chain, or up the food pyramid. As apex predators, Peregrines were especially susceptible to the dangers of these chemicals.

As with Brown Pelicans, which we talked about in a previous blog, DDT caused the shells of Peregrine Falcon eggs to become unnaturally thin. Brooding falcons would accidentally crush their own eggs. This caused a catastrophic drop in falcon populations over several decades.

The species eventually received legal protection in the 1970s. This, and perhaps more importantly, the banning of DDT through much of the world, allowed Peregrines to make a dramatic comeback.

We also owe the success of this bird’s recovery, in part, to the efforts of private conservation organizations such as the Peregrine Fund as well as some falconry groups. Today these birds are doing much, much better. They still face multiple threats, for sure, but their population numbers are stable across most of their vast range.

Once a bird of only remote, windswept cliffs in wild places, the Peregrine has, amazingly, become a familiar bird in many cities around the world.

You can guess which two factors make our concrete and steel landscapes appealing to these falcons. (1) Our skyscrapers and overpasses might as well be big cliffs, from their perspective. Great spots for raising a little falcon family. And (2) Cities are chock-full of plump pigeons, one of the Peregrine’s favorite foods.

So in cities like New York, London, Singapore, and Sydney, three cosmopolitan animals now live side-by-side. One of them is the self-proclaimed smartest of all animals. One of them is slightly smaller than a crow and is fancied by Mike Tyson. And one of them is the fastest animal on the planet.

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