The Science of Birds - Peregrine Falcon

Episode Date: December 5, 2020

This episode is all about the Peregrine Falcon (Falco peregrinus), of the family Falconidae.Learn about this incredible bird's key features, its global diversity, feeding behavior, and more.Links of InterestShort video about Peregrine FalconsPeregrine Falcons under threat from systematic persecution, says RSPBLink to this episode on the Science of Birds websiteSupport the show

A handful of bird species are said to be cosmopolitan. Now, I'm not talking about a ladies' glamour magazine or a cranberry-flavored cocktail. The word 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. Now, I can just see the kid in the back of the class shoot her hand up and she's like, But Mr. Philipson, that's not true because I read that the common pigeon, technically known as the rock dove or rock pigeon, Columba Livia, well, it lives all over the world and it lives in more places than any other bird. Okay, yes, that's true, smarty pants.

But the reason rock pigeons live everywhere is because humans domesticated them long ago and we've also moved them around the planet. So, if we ignore, for now, species with unnatural distributions, we can return to the peregrine falcon. Not only is this bird of prey the most cosmopolitan of all feathered animals, it's also more widespread than just about every mammal. So, dear listener, wherever you are in the world right now, there's a good chance you have peregrine falcons bolting through your airspace, at least occasionally. Unless you're in New Zealand, then you're out of luck. Sorry. We have these amazing raptors in Oregon, where I live. There's a beautiful spot on the Pacific coast about an hour from here.

There's a high black cliff that overlooks a sheltered bay. Gulls, cormorants, and gillamots perch on the cliff and wheel through the gulf of air below it. Near the top of the precipice is a peregrine falcon airy, where a pair make their nest every year. Erie is spelled E Y-R-I-E. The cormorants and other birds flapping around nearby provide an endless bounty of food for the falcons and their chicks. I've also seen peregrins in remote places like Mexico's Sea of Cortez and in the tropical islands of New Caledonia in the western Pacific Ocean. Maybe you've seen them in even wilder places. The name peregrine comes from the Latin word for foreigner or traveler.

It's said that medieval falconers used to capture adult peregrine falcons during, the bird's migrations. Maybe the falconers did that instead of risking their necks by climbing hundreds of feet up sheer cliffs to steal chicks from the nest. In any case, these days, the interpretation of the word peregrine is often given as wanderer. Seems like a fitting name for a bird found all over the world. Now, I seem to recall there's something else about the peregrine falcon, some interesting

bit of trivia or something. Oh yeah, it's really fast. But I'm sure you've heard that before and I doubt it's worth talking about here. I mean, I don't want to bore you. Just kidding, we're totally going to talk about the ridiculous high-speed antics of the Peregrine. How could we not? Hello and welcome.

This is the science of birds. I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted, guided exploration of bird biology for lifelong learners. This episode is all about the Peregrine Falcon, Falco Peregrinous. This is the first time I've written a whole episode about a single species. I really hope you enjoy it. I plan to sprinkle more single species episodes like this among those that focus on larger biological topics, or those that focus on whole bird families.

The Paragon Falcon is one of the most well-study birds around. That means there's lots of good stuff we can learn about this species. So let's get on with it already. What are the key features of the Paragon Falcon? We'll take a few minutes to do an overview, then venture forth into more of the sciencey details. 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. These taper to sharp points. The bird's wing beats are deep and fluid. Its tail is on the longish side. Seeing this shape alone may be enough for you to identify a peregrine falcon. this bird is roughly the size of a crow and you know

I think the crow has become sort of like the bread box of the avian world remember when people would ask is such and such bigger than a breadbox the breadbox was the size standard by which all things were compared this is an American saying I think

I'm still tempted to use it sometimes but then I remember I've never actually seen a breadbox and I have no idea how big one is but I sure have seen a crow or two and I'm guessing that you too are no stranger to the shiny black birds of the genus Corvus. How big was Archaeopteryx? About the size of a crow. How big is a pilliated woodpecker? About the size of a crow? Maybe we can replace the breadbox with the crow in all facets of life.

So, doctor, about this tumor in my brain. Is it bigger than a crow? Anyway, 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 falcons' wings, as I mentioned, taper to a neat point. The sickle shape of the wings makes them superbly adapted for fast flight and aerial agility. We see a similar wing shape in swallows, swifts, plovers, and other speedy flyers.

Paragans routinely zoom around at 30 to 50 miles per hour, which is 48 to 80 kilometers per hour, and 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 paragon 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. 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 mallor stripe. In some populations, these markings are narrow and truly stripe-like. In other populations, they spread out to cover the whole cheek. One hypothesis is that these mallor stripes work the same way as the eye-black grease used by football players, baseball players, and other sports people. 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.

Another possibility, at least with the athletes, is that they put black grease on their faces just because they're trying to look cool. But I don't think peregrins and cheetahs have to try to be cool. They just are. The keen eyes of a paragon falcon are large and, dare I say, expressive. They're a rich brown color and are surrounded by contrasting yellow eyelids and facial skin. 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 tomeal tooth is just a specialized protrusion of the upper beak's keratin sheath. All falcons have tomeal teeth. We'll talk about what they're used for in just a bit. As for other key features of the paragon 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 paragon falcon is the fastest animal on the planet. This falcon eats other birds. That's its thing. And to catch birds in the you need to be fast and you need to be maneuverable. Peregrins are both. We'll come back in a few minutes to look at the details of how these falcons hunt. But first, let's have a look see at the diversity among peregrine falcons across the world and at their relationships to other types of birds. Paragrin's are in the family falconidae.

This family includes about 65 species of falcons, kestero, and Caracaras. We'll do a whole episode on this family at some point. Many bird field guides are organized taxonomically, with more primitive slash ancient bird families in the beginning and more recently evolved birds toward the end. Back in the day, well 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, published in 2016, has woodpeckers, then falcons, then parrots. Falcons are nowhere near hawks and eagles in that book. 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 over 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 were 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 Paragrin-Falcan 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 this low level of subspecies distinctiveness at the genetic level is that the Paragon 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 paragon 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. 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? This bird lives on all of the continents.

All of them, that is, except for, don't make me say it. Okay, you made me say it, Antarctica. So where else doesn't the Paragon 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. But 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, the imaginatively named New Zealand falcon, Falco Novisilandii. Maybe peregrins 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 generally aren't great flocks of parrots. 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 freaking 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 diagram 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. Peregrins are territorial in the breeding season and don't tolerate trespassers they 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, from tundra to 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 airspace. 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. This brings us, at long last, to the amazing way that Peregrins catch their prey. Let's talk about that now.

You know that the diet of the paragon falcon is mostly birds. Between 77 and 99% of all the prey critters eaten by peregrins are birds. On the menu are many birds that are smaller than a crow, like songbirds, than 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 peregrins 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 have 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 Paragon 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 Petrol, and Shearwater families. Puffins are in the Auk family, so for those adorable puffins that we all love, the Paragon Falcon is the stuff of nightmares. Besides birds, the next most frequent victims of this falcon are bats. In places like Texas and Brazil, peregrins catch bats at sunset.

They sometimes eat bats while flying. In one example, a falcon in the Grand Canyon ate seven bats in 20 minutes without ever landing. Okay, now I'm going to lay out how a paragon falcon typically hunts and kills birds. The basic stages are search, pursuit, capture, killing, and eating. We'll stop there and skip the digesting stage and what inevitably comes after that. Searching for prey usually takes place from a perch on a high vantage point. Cliffs are the best. Like other raptors, the Paragon 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 they can see motions that would just look like a blur to you and me I did a whole episode on the vision of birds so check that out if you'd like to learn more about this that was episode 7 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. Paragon 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, and so on. But their most famous method of operation, and the one will discuss here. 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, usually from thousands of feet 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 stream. 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. And 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, which is such a great name. Ken is a skydiver, and he trained Frightful to chase him as he leaped out of planes and plummeted to 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, right? To match speeds and free fall side by side with a Perrigan Falcon, who also happened to be your little buddy? Okay, so back to our example bird, presently rocketing toward its prey below. 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 peregrins 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 in-rushing 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, as in the letter M. 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. hey there i just wanted to take a quick break to sip some coffee and i have a little favor to ask of you if you're digging the science of birds podcast and getting some value from it i would really appreciate getting a review from you if you're listening on apple podcasts you can leave a review that way otherwise a great place to leave me a review is at podchaser dot com podchaser dot com just look up the science of birds and you can leave a review there clickety click click. I would really, really appreciate it. Thank you. Now, let's get back to those birds. 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 paragon 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 bird can swoop around to strike again, or snatch a stunned bird that's now tumbling to the ground. So now we're at the killing stage. Sorry, kids, but this program, is rated BV for some descriptions of moderate bird-on-bird violence. 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 sort of a fist to deliver this killing blow. But now there seems to be some uncertainty about that, whether or not it's true. 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. But the paragon falcon uses another pointy weapon, its tomeal tooth.

Well, its tomeal teeth, rather, both of them. While still in flight or after landing, the falcon bites into the back of its victim's neck. The toomeal teeth are used to separate the cervical vertebrae and sever the spinal cord. Our falcon, now 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 its meal. Grusome, 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 eaten 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 paragon 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 paragon 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 paragon falcons include bald eagles, golden eagles, rough-legged and red-tailed hawks, jeer falcons, ravens, gulls of various flavors, and more. If you look at the global range map of the paragon 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 pereons 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 paraguans 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, and that's one way. But even birds that breed at high latitudes sometimes stay put year-round. Some paragon falcons living in Alaska's Aleutian islands, for example, 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 peregrins 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, Paragrin Falcons are monogamous. The female and males stay together through the breeding season, but usually do their own thing in the non-breeding season.

The pair reunites 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, like this. And they display to each other in several ways, including flashy aerial performances complete with loop-de-loops, barrel, zigzags, and figure-eights. Most often it's the male who does all this. the nest of the paragon 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 paragons 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 peregrins, a pair of grins, mate and then pop out a few eggs, both parents help to raise the babies. On average, one or two 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 eerie, the territory owners will attack. Fighting falcons grab each other with their talons and bite each other's heads and neck. These gnarly brawls can last for hours and can result in one bird being killed. Eagles, hawks, owls, and jeer falcons are

predators of peregrins, especially the chicks. So if one of these predators trespasses on a peregrine's territory, it's often seen as a threat. There are cases where threatened peregrins 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 paragon 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, Paragrin 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. How dare those falcons eat the birds that we plan to blast out of the sky for mere sport? Another group that has persecuted Peregrins is pigeon fanciers. pigeon fanciers sometimes shoot or poison falcons to protect their weird 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 peregrins in the UK today

is illegal persecution from gamekeepers and pigeon fanciers apparently the boxer Mike Tyson is a pigeon fancier so I guess I'll hold my tongue before I say anything more that might get me punched in the face. 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, peregrins were especially susceptible to the dangers of these chemicals. As with brown pelicans, which we talked about in episode 14, DDT caused the shells of peregrine falcon eggs to become unnaturally thin. Brewing 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 peregrins 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 which helped with captive breeding programs. 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, wind-swept 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. One, our skyscrapers and overpasses might as well be big cliffs from their perspective, great spots for raising a little falcon family. And two, 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. As is true for so many topics on this podcast, there's much more that could be said about the Perrigan Falcon. But I hope this was enough to entertain you and help you learn a thing or two about these superlative creatures. Thanks so much for listening. I hope you'll check out more of my podcast episodes. And if you have thoughts or feelings about the show or you want to tell me where you've seen

Perrigan Falcons, shoot an email to Ivan at scienceofbirds.com. You can see the show notes for this episode, which is number 16, on the science of birds website, scienceofbirds.com. This is Ivan Philipson, and I'll catch you next time. Peace.