The Science of Birds - The Common Kingfisher

Episode Date: August 21, 2024

In this episode—which is Number 102—we dive into the fascinating world of the Common Kingfisher (Alcedo atthis), a small but mighty bird known for its striking blue and orange plumage and remarkable fish-hunting skills. We'll look at this species' behavior, from its iconic plunges into water to catch prey, to how it breeds, including courtship rituals, nest-building, and the challenges of raising chicks.Learn about the kingfisher's diet and foraging strategies, including how it deals with challenges like refraction at the water’s surface to accurately target its prey. Additionally, I touch on the habitat and global distribution of the Common Kingfisher.This episode offers a fun exploration of one of the most beloved birds in Eurasia. Tune in to learn more about the "Prince of Piscivory."Links of InterestKingfisher Diving in Slow Motion [VIDEO]Kingfisher Coughing up a Pellet [VIDEO]Two male kingfishers fighting [VIDEO]Kingfisher family in the nest cavity [VIDEO]~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

It's a quiet summer morning on a side channel of the Danube River, not far from Vienna-Austria. The water flows slowly past the green banks lined with poplars, willows, and dogwoods. On one branch, thin and bending towards the rippling water, there sits a compact bundle of blue and orange. It's a bird, one whose head seems two sizes too big for its small body. Its long, dagger-shaped bill seems even more out of proportion with the rest of the ensemble. After some long minutes on its perch, waiting and watching, the bird suddenly darts straight down into the water in a blur of blue and orange. It disappears with a splash. A heartbeat later, the bird bursts

back into the air and reclaims its perch. But now it has a wiggling minnow in its bill. Time for breakfast. Scenes like this have played out, with and without human witnesses, along the clear, slow-flowing waters of Europe and Asia for millennia. The bird we're talking about is none other than the Prince of Piscivary, that monarch of minnows. Yes, it's the kingfisher. The common kingfisher is well known and well-loved by people across its extensive geographic range. Not only does it have beautiful plumage, its fish-catching behavior never fails to be entertaining and impressive. Hello and welcome. This is the science of birds. I am your host, Ivan Philipson.

The Science of Birds podcast is a lighthearted exploration of bird biology for lifelong learners. This episode, which is number 102, is all about the Common Kingfisher. Not to be confused with the 1991 film The Fisher King, starring Robin Williams and Jeff Bridges. That's a good movie, but that's not what we're talking about today. The Common Kingfisher has the scientific name, Alcido. at this. The genus name Alcedo is spelled A-L-C-E-O. This word is derived from the Latin word of the same spelling Al-Sido. It means Kingfisher. The Latin word itself has its roots in the Greek word halcyon, which also refers to a kingfisher. In fact, there's another genus in the

Kingfisher family named Halcyon. The second part, the specific epithet of the common Kingfisher, Fisher's scientific name, At This, was the name of a beautiful young woman who featured in some poems in ancient Greece. That word is spelled A-T-T-H-I-S. Sort of like, at this very moment, I'm wearing pajamas, which is 100% true. One of the great things about working from home, doing things like making a podcast, is that you get to work in your pajamas, if you want to. So I don't know, maybe picturing me in pajamas at this very very. moment will help you remember the specific epithet of the common kingfisher. So the next time you're on a TV quiz show like Jeopardy and you have to remember the scientific name of the common kingfisher,

what is it? Alcido Atthis. It was the wonderful members of my Patreon community who chose the species for this episode. I put out a poll and asked them to vote. The choice was between the common kingfisher and the superb fairy wren, which is a well-known songbird in Australia. The poll results were 63% for the kingfisher and 37% for the fairy wren. Now, neither of these birds is found in the Western Hemisphere. From day one when I started this podcast, I wanted to make sure the focus is on more than just the birds of North America. I want to highlight the fascinating biology and incredible diversity of birds all across

the planet. Anyway, North America has its own common kingfisher. But in this case, I mean common with a lowercase sea. The most widespread, most common kingfisher species in North America, by far is the belted kingfisher. That species is definitely worthy of its own podcast episode. And so one day it shall be. But today we're giving some love to the common kingfisher of Eurasia. and that's common with a capital sea. But many people in the UK and elsewhere in Europe know this species as just the kingfisher, because it's the only kingfisher species across most of Europe.

At least from a narrow European point of view, this bird is the OG kingfisher. Of the 117 species in the kingfisher family, Alcido at this has the largest geographic range. Given its familiarity and broad distribution, I thought there would be tons of information out there about the common kingfisher. But surprisingly, not so much. But there's still much we can discuss. So hold your breath because it's time for us to take the plunge. Let's begin with the appearance.

of our little beast. The common king fisher has a basic body plan that's typical for species in its family, Alcadinity. For starters, this bird has a compact body. Or, as one author put it, a, quote, dumpy body. Geez, not a very flattering way to put it.

But not technically wrong. Other acceptable adjectives here include stubby, stout, and chunky. But what you're more likely likely to notice on this bird is its head, its big old comically oversized bobblehead. And the beak seems way too large as well. It's long and shaped like a spear or dagger, flattened from side to side with a sharp point at the end. The common kingfisher's bill is so well adapted with its streamlined shape that human engineers used it for inspiration

when redesigning bullet trains in Japan. The kingfisher-esque nose cone. of some bullet trains allow them to cut through the air at high speed in a way that prevents sonic booms from happening. Because that used to be a real problem. So, the kingfisher has this massive noggin and bill. You have to wonder how it's able to support all that weight. I mean, the bird looks very top-heavy. Like, if your six-year-old came up to you and said, Look, mommy, I drew a kingfisher for you. You might look at the colorful scribbling, and say, oh, that's, uh, wow, Timmy, you're a very good artist. Thank you. But if I can just give you a little constructive criticism, I think maybe you made the kingfish's head a little too big. But you, mummy, are wrong,

because Timmy, who is now sobbing hysterically, thank you very much, is in fact a very good artist, and his drawing captured the bird's body proportions perfectly. Such exaggerated proportions are not unique to the common kingfisher, because, as I mentioned, this body type is typical for birds in its family. The wings of the common kingfisher are fairly short and rounded, and the tail is super short. This combination of short wings, short tail, and a dumpy body make the kingfisher highly maneuverable in flight. When traveling from one place to another, it usually flies fast and direct, with rapid wing beats, and often close to the water's surface. In terms of size, this is a pretty small bird.

From beak to tail, it's between six and seven inches long, or between 16 and 18 centimeters. The wingspan is 10 inches or 25 centimeters. To further accentuate the comical body proportions of the kingfisher, we have the bird's feet. There are teeny tiny little things. And like other kingfishers, Alcido at this has an interesting arrangement of its toes. The most familiar common foot arrangement among other birds is where three toes point forward and one backward. This is typical of perching birds like sparrows, finches, etc. Ornithologists call that type of foot anacidactyl, spelled A-N-I-S-O-D-A-C-T-Y-L.

But kingfishers have sin-dactyl feet. That's S-Y-N-D-A-C-T-Y-L. The word syn-dactyl comes from the Greek words sin, meaning together, and dactylos meaning finger. A syndactal bird foot has two or more toes that are sort of fused together. In our kingfisher, the outer two toes are connected along most of their length. But it's not because the bones themselves are fused. It's only the soft tissue surrounding the bones that bind the toes together. No one knows for sure why some birds like kingfishers have these syndactal feet. But it could be that having toes that are partially fused helps distribute the bird's weight more evenly and reduces the risk of slipping from a wet tree branch.

In terms of color, the legs and feet of adult kingfishers are in all. almost fluorescent orange-red color. But youngsters, the fledglings, have black legs. It takes them two to three months to develop that bright orange color. As I mentioned at the beginning of the episode, the plumage of the common kingfisher is dominated by blue and orange colors. The overall impression is strikingly vibrant, with upper parts that are mostly blue-green and rufous orange underparts.

There are also some orange feathers. called the ear coverts that form a patch just behind and below the eye. The midline of the back and rump is more of a bright blue or azure color. The throat, chin, and sides of the neck are white. The blue-green crown and nape have small blackish barring that can sometimes look like spots. Some researchers have looked at the microscopic structure of common kingfisher feathers. This structure can reveal how the feathers get their colors.

Remember that blue feathers in birds get their color from the way their microscopic structures and melanin pigments interact with light. I talked about that in episode 56, which was titled How Bird Feathers Get Their Colors. What those researchers discovered was that the wing feathers of the common kingfisher have some blue colors that shine in the ultraviolet end of the spectrum. Humans can't see ultraviolet colors, but birds can. So when common kingfishers look at each other, they probably appear even more colorful than they do to us. At first glance, males and females in this species seem to be more or less identical. But there is a quick way to determine the sex of adult common kingfishers.

If this was the 1940s and we were in a Bugs Bunny cartoon, I'd say the female is easily recognizable because she has elegant eyelashes and red lipstick on her beak. But thankfully, that's not the case. In the real world, we can identify the female, the queen fisher, if you will, by the color of her lower bill, which is mostly orange, but it has a black tip. In contrast, the male's bill is entirely black. Immature or juvenile common kingfishers resemble the adults, but they have duller, greener feathers on their backs, and their undersides are dull orange or even brownish.

Most Kingfisher species don't make very complex vocal sounds, and that's certainly true for the common Kingfisher, but it does make a few distinct calls. One is a high-pitched whistle, often made during flight or when alarmed. This sound is variously described in guidebooks as Chi-Chi or Z-Z. Here's an example. Then there's a slightly more harsh sound that's used as an alarm or threat call. I believe the sound in this next recording is one of these threat calls. It sounds to me kind of like a cricket chirping.

Yeah, I'd say that's. It's pretty threatening. I mean, what if I'm about to go over and harass that kingfisher? But then it busts out with its threatening cricket sound. I stop dead in my tracks and back away with my hands up, palms forward. Oh, hey, I'm sorry, mister. I didn't mean no harm. Honest. I was just fooling around. No need to get angry. We're all friends here, right? The name of the Kingfisher family is Alcadignity. I did an entire episode on this family, and that was way back in episode 20.

There are 18 genera in the family Alcadinity, including Alcido. Besides the common kingfisher, there are seven other species in the genus Alcito. The sister species of our bird of interest today, its closest relative, is the small blue kingfisher. That's the full name, small blue kingfisher, with all three words capitalized. Its plumage is sky blue with white accents. The scientific name of this bird is Alcido Cyrillessens, and another common name for it is the cerulean kingfisher. Interestingly, the small blue or cerulean kingfisher lives only on the islands of southwestern Indonesia. Because of the close relationship between the common and small blue kingfishers,

scientists have suggested that the common kingfisher first evolved on one of those tropical islands. And then it spread far to the north and west. And in the process, it introduced a new form of terror to the small fish of Asia and Europe. Common kingfishers across that broad range today don't all look identical. If we consider the diversity within the species, ornithologists currently recognize seven subspecies. As far as I know, these subspecies have been defined by ornithologists using only physical characteristics like plumage and size, as well as their geographic ranges. For example, a couple of the subspecies found in the central and eastern parts of the Indonesian archipelago have

blue ear coverts, rather than orange, which is the typical color. But I couldn't find any published research on genetic differences among the subspecies. The Common Kingfisher has such a large geographic range. I won't be surprised if future genetic research reveals that it represents not one, but two or more species. Some subspecies might get elevated to full species status someday. Something like that happened recently for another widespread bird, the olive-backed sunbird. A 2023 study using data from olive-backed sunbird DNA revealed a bunch of significant genetic

differences among some populations. And so that motivated ornithologists to split that one species into eight species. So maybe they'll split the common kingfisher into several new species someday. I vote we name one of them the dumpy kingfisher. So we've established that the common kingfisher has the largest geographic range of any kingfisher. You can find these birds across much of Europe, Asia, and parts of North Africa. In Europe, the common kingfishers range includes Ireland, the United Kingdom, and much of mainland Europe, stretching from Portugal and Spain in the west to the Ural Mountains in Russia.

In Asia, the common kingfisher is found. around across the southern and central parts, including India, Southeast Asia, eastern China, Japan, and parts of Siberia. Its range extends southward to Indonesia, the Philippines, and the Solomon Islands. Not surprisingly, these kingfishers are absent from the arid grasslands and major deserts of Asia and northern Africa. But I do think it's surprising that this species is mostly absent from the island of New Guinea. for some mysterious reason.

My best guess for why this strange gap in the common kingfishers range exists is that there are a bunch of other kingfishers species that it would have to compete with on the island of New Guinea. Over 30 other kingfisher species live on the island. Who knows? Anyway, let's talk about the habitats of the common kingfisher. Essential habitat features for this bird include still or slowly flowing water with abundant small fish. The water should be clear so the kingfishers can actually see their fishy prey.

Plenty of tree roots or branches, reeds, rushes, or shrubs on the banks should be available for perching. In the breeding season, there need to be suitable banks for nesting. Streams, small rivers, and canals are better than open water, but kingfishers will also use lakes, ponds, and flooded gravel pits. During winter, common kingfishers in some inland populations will head to the coast, where they hang out in estuaries, harbors, and along rocky seashores. If you've got a stream or other water body and it's swarming with dumpy little blue and orange kingfishers, well, that's a good thing. sign that the ecosystem there is healthy. Some scientists consider this bird to be a reliable indicator of freshwater community health, because common kingfishers thrive only where the water is clear and clean, full of healthy fish, and fringed by rich vegetation. Some populations of the

common kingfisher are year-round residence, while others are migratory. In colder regions like northern Europe and Siberia, many of these birds will move to milder areas during winter to make sure they have access to unfrozen water sources. For example, kingfishers that breed in Siberia often fly over 1,800 miles or 3,000 kilometers south for the winter, spending the non-breeding season in southeast or southern Asia. Winter presents a significant challenge to the survival of common kingfishers in northern populations, primarily when water bodies freeze. If all the water is frozen, the kingfishers can't eat. It's like what would happen to me if my microwave broke? I might literally starve if I can't make my hot pockets. There's a strong correlation between

winter severity and kingfishers survival. A study analyzing Mark recapture data from Slovakian and Czech Republic populations, found that apparent survival rates were lowest in 2017, a year with exceptionally harsh winter conditions. During that winter, temperatures plummeted to minus 13 degrees Fahrenheit or minus 25 degrees Celsius for over three weeks, and that caused water bodies to freeze completely. In some cases, it's actually the adult kingfishers that may be at the highest risk of starving in winter, because they're more likely to stick around and spend the winter near their breeding territories. Juveniles, on the other hand, tend to migrate long distances, spending the winter in warmer places. The common kingfisher has an estimated global population

between 700,000 and 1.5 million, and that's just a very rough estimate. In any case, this is not considered to be a threatened species at the global level. It's not likely to go extinct anytime soon. Population trend data aren't available for most regions. But in Europe, the common kingfisher's populations appear to be decreasing. One estimate from 2015 was a decline of 30 to 49% over about 13 years. So that's not good. The major threats to this bird have to do with the health and management of aquatic habitats. Common kingfishers are sensitive to pollution in streams and rivers. Chemicals that drain into these water bodies come from agricultural and industrial wastes. On top of that, humans have reshaped and modified natural rivers in many

places, sometimes to the point of being unrecognizable. We clear away natural vegetation from the banks, straighten and channelize watercourses, pave over the banks with concrete, and so on. Fish and other aquatic animals can't survive in such artificial environments, and neither can kingfishers. Thankfully, outright persecution of common kingfishers is probably not all that common, anymore, because back in the day, these birds were sometimes killed because they were thought to compete with fishermen. They were also hunted. for their colorful feathers, which were used in the fashion trade. You know, for dumb stuff like making fancy hats.

As for competition with fishermen or fisher people, yes, there may be some evidence that common kingfishers have localized impacts on certain fish populations, particularly in controlled environments like fish farms or heavily stocked ponds. But the overall impact of these birds on fish populations of, commercial or recreational value is generally low in natural settings. Other factors like habitat quality and human shenanigans play a much larger role in determining the health of fish populations. Okay, now we're getting to the main event. We're going to look at

diet and foraging behavior of the common kingfisher, because of course the real claim to fame for this bird is the way it hunts. I'm guessing you've seen some of those slow motion videos of a kingfisher diving and catching fish. It's an absolutely amazing thing to see. I'll put a link to a video in the show notes if you want to check it out. Like many small birds, the kingfisher needs a lot of calories to fuel its high metabolism and energetic lifestyle. It needs to eat roughly 50 to 60% of its body weight every day. So that's something like 10 to 20 small fish per day. It's fun to think about what that would mean for a human. If I needed to consume 60% of my body weight in one day, I'd need to eat no less than 355 hot pockets. Or,

8,000 tater tots. That's a lot of tots, yo! I usually cut myself off after about 800. Most of the small critters that end up in the belly of a kingfisher are indeed fish. Small ones, up to about five inches or 12 centimeters long. The average size, however, is pretty tiny at only about an inch long or 2.5 centimeters. We're talking fish like minnows, sticklebacks, and dace. Common kingfishers also eat the babies of larger fish species like trout, perch, pike, and carp. The particular fish species targeted by a common kingfisher will naturally depend on where that bird lives. With such a vast geographic range, there are many, many different fish species that are potential prey for these kingfishers. Common kingfishers

will also hunt other small animals besides fish. They eat aquatic insects, crustaceans, frogs, and amphibian larvae. Basically any small wiggly or crawly thing that's in the water. Non-fish prey can make up something like 10 to 30 percent of a kingfishers diet. Fish can be hard to come by in winter compared to the summer breeding season. So kingfishers will sometimes switch to eating more of those non-fish prey like insects in the winter. Like any good fisher person, a kingfisher must have a lot of patience. The bird will sit on a perch, usually over water, between three to seven feet or one to two meters above the surface. It might sit there for a long time before anything catches its

eye. The kingfisher bobs its head up and down and around as it scans the water for movement. These little head movements improve the bird's ability to determine the distance to and depth of its prey. And that's the challenge, right? The kingfisher has to pinpoint the location of its tiny prey with a high level of accuracy. The eyes of the common kingfisher have a couple of adaptations that make this possible. First, the eyes have two modes, monocular mode and binocular mode. Many kinds of birds have only monocular vision, but kingfishers have both. When both eyes can look forward and see the same object at the same time, that provides binocular vision, which is ideal for depth perception.

But interestingly, when it's just sitting there, scanning the environment for movement, a kingfisher generally uses just its monocular vision. That's why those headbobs are helpful. They improve the bird's ability to estimate distance, while in monocular mode. Unlike humans who have a broad binocular field of view, a kingfisher has only a narrow band of binocular vision, just straight ahead and aligned along the length of its bill.

But that's enough to do the job, apparently. This comes into play once the bird makes its move when it rockets downward to catch a fish. In an instant, it switches to binocular vision mode to get the best possible estimate of the fish's location. But there's a problem, the problem of refraction at the water's surface. Refraction is a sort of optical illusion. It occurs because light changes speed and therefore its direction

as it moves from one medium to another, such as from air to water. This bending of light makes an object like a fish under the water appear to be at a slightly different location than it actually is. If the kingfisher doesn't adjust for the illusion of refraction, it's probably going to miss its target. One way a kingfisher minimizes the problem of refraction is to dive almost vertically into the water. A steep diving angle is helpful because the illusion caused by refraction is less severe when looking straight down compared to when you're at a shallower angle. But still, kingfishers don't always make vertical dives. So their little kingfisher brains seem to have a special ability to compensate for refraction. They may have a

specialized neural processing ability that helps them to correct for the distorted images they see when looking into the water. Their brains might be wired to quickly adjust for the difference between the apparent and actual positions of their prey. It's like when I'm birding from my car, swerving around and driving recklessly on a country road, then I see a cop car with its flashing lights in my rearview mirror. I know that objects in mirror are closer than they appear, and specialized neural processing in my brain

allows me to calculate the actual position of the cop car. I calculate the probability of being able to outrun the cop if I slam on the gas. But then, I remember I'm driving a 2003 Chrysler PT cruiser. Probability of outrunning the cop? Zero. But back to the kingfisher. We're following it in slow motion as it makes a steep dive to the water.

You know, I have to wonder if the gigantic fun co-pop head of the kingfisher, combined with its tiny feet and stubby tail, make it better at diving. It's got a heavy end and a light end. like an aerial bomb dropped from a military plane, or like a lawn dart. Remember the game, lawn darts? No? Well, maybe that's because you were born after 1988 when lawn darts were banned, at least here in the U.S.

Even as a kid, I remember thinking, seriously, they're letting us play with these things? These giant metal darts that might as well have the slogan, Death from Above? Well, as our living lawn dart, the kingfisher, breaks the surface, a couple things happen with its eyes. Tiny muscles in each eye change the shape of the lens rapidly to focus underwater. And even with that, visual acuity isn't as good under water for the bird as it is in the air. But it doesn't need to be. It just needs to be good enough

for the kingfisher to locate its prey. The other thing that happens is that the third eyelid slides across the eye to protect it. This is sort of like having built-in swim goggles. All birds have this third eyelid called a nictitating membrane. It slides across the eye horizontally. When a kingfisher hits the water, its nictitating membranes cover its eyes. And since the membranes are transparent,

the bird can still see. Just after it drops below the water surface, the kingfisher opens its wings. It will dive to a depth between a few inches and three feet, or up to one meter. Usually the dive is less than a foot deep, however. The dagger-like bill is beautifully streamlined for piercing the water. And you'd think that the bill is also used to pierce the fish, like a spear. But that's not what happens.

The kingfisher actually opens its beak up in the instant before impact, using it more like tongs or tweezers. So the unlucky fish gets snatched up. The kingfisher flaps its wings and relies on its own buoyancy to rise quickly back to the surface. It bursts out of the water and shoots up to its perch. The moment that a common kingfisher emerges victorious from the water with a fish in its bill is so iconic that there's a Lego set of that exact scene. I'm 100% serious.

It's in a Lego series called Icons, and this set is called Kingfisher Bird, and it'll set you back 50 bucks if you want to buy it. Crazy. Anyway, our triumphant kingfisher is back on its perch. At this point, the little fish may not have accepted its fate yet. It might be thrashing around trying to get free. In that case, it's time for a severe beating. The bird holds the fish by the tail end and then wax the fish hard on the tree branch or whatever. Once the fish gives up or is stunned or killed, the kingfisher repositions it and swallows it head first, down the gullet. This slamming behavior is not unique to the common kingfisher. We see it in other kingfishers and in the close relatives of kingfishers, like bee eaters, rollers, and motmots. I don't think there's

a lot of hard scientific data on the success rate of dives in common kingfishers. But from what I could find, it seems they catch a fish in about 50 to 70 percent of their dives. And can you imagine how scary it would be to be a fish living in a world haunted by kingfishers? I mean, you're swimming around in your tranquil, watery home, doopty-do, oblivious to what's going on above the surface, then out of nowhere, bursting through an inter-demand, portal in the sky, this vicious blue and orange monster lunges at you with its giant spear-tipped face. I mean, holy moly. But common kingfishers aren't always a source of pure terror. Sometimes they do things that are actually pretty cute. For example, there was this study on river otters conducted

in Spain. The researchers followed some otter families around for a few weeks, observing the playful mammals as they hunted for fish and generally horsed around. Well, about one-third of the time that otters were swimming and frolicking in streams and rivers, they were followed closely by common kingfishers. The birds were snatching up small fish stirred up or otherwise left in the wake of the otters. In this adorable relationship between two species, the kingfishers benefit by getting easy access to some fishy snacks. And the otters get nothing. The otters don't seem to benefit from the presence of the kingfishers. But the birds don't bother the otters. So this is an example of an interspecies

relationship that biologists call commensalism. In commensalism, one species benefits while the other species is unaffected. The last thing I want to tell you about feeding in common kingfishers has to do with barf. Our little kingfisher hacks up pellets in a way similar to what owls and other raptors do. All those fish, aquatic insects, and crustaceans have some crunchy or spiky bits that don't go down smoothly. Those bits and pieces are more or less indigestible to the kingfisher. So a few times a day, the bird regurgitates a compact gray pellet of fish and invertebrate body parts. Ornithologists can often figure out what a kingfisher has been eating

by picking apart and analyzing the contents of its pellets, similar to how we study the diets of raptors. Some of those pellets end up as permanent fixtures in the kingfisher nest. I'll put a link in the show notes to a video of a kingfisher in its nest, hagging up a pellet and then purposefully smoohing it into the floor of its nest. And since I mentioned nests, we should present. probably move on, at this time, to talk about the process of making baby kingfishers. The common kingfisher is a socially monogamous species. Breeding pairs consist of one male and

one female. However, genetic analyses have revealed that extra pair fertilizations do happen sometimes. Extra pair fertilizations are where some offspring in a nest are fathered by a male other than the one in the breeding pair. This sort of breeding behavior is rampant in many other bird species, but extra pair paternity or fertilization is thought to be rare in the common kingfisher. Pairs of kingfishers form through the process of courtship, but it seems they pair up only begrudgingly, because common kingfishers are solitary creatures at heart. Some naturalists have observed that certain courtship behaviors in these birds look a lot like the aggressive territorial displays they perform for their enemies.

They navigate their courtship interactions with a bit of tension and awkwardness, sort of like the cringe-worthy courtship displays some of us humans blundered through in junior high. Once a male and female kingfisher have agreed to set aside their mutual dislike for each other, at least temporarily, they get on with the show, for the greater good of perpetuating the species. The key feature of pair formation is the ritual of courtship feeding. The male catches a fish and then presents it to the female as a gift. Courtship feeding serves multiple purposes. First, the male showcases his ability to provide food for the female and their potential offspring,

which would be crucial for the survival of the chicks. Second, courtship feeding helps to establish and strengthen the bond between the male and female. It's often repeated multiple times during the courtship period. Common Kingfishers are highly territorial little buggers. They defend their hunting and nesting areas fiercely. Remember that they each need to eat the equivalent of like 8,000 tater tots every day, so having control over a good fishing spot is essential for their survival. A typical territory is a stretch of clear, slow-flowing water with well-vegetated banks.

It's usually at least 0.6 miles long, but can be up to 2.2 miles long. That's 1 to 3.5 kilometers. A kingfisher will go on the offensive if a trespasser, shows up in his or her territory. The territory holder starts by making threat displays and calls from a perch, swaying side to side, crouching, stretching its neck out, drooping its wings, and opening its bill aggressively. But given the similarity in courtship and territorial behaviors, I wonder if the trespassing

bird can get confused when facing off with a territory holder. Maybe the trespasser is like, Wait, wait, wait, time out. I'm sorry. I'm trying to read your body language, but I can't tell if you want to kill me or if you want to make out with me. Which is it? If all those threatening slash seductive displays don't scare off the interloper, the territory holder will try to chase it off.

The two birds may even end up fighting, grappling each other with their bills and tussling with their wings flapping furiously. One bird will sometimes try to hold the other one underwater. I'll put a link in the show notes to a video of two male kingfishers threatening each other and fighting in and out of the water. Now let's say the intended effect was indeed seduction. After a male and female pair up, it's time to make a nest. Common kingfishers dig burrows in vertical river banks to nest.

Both parents help with the excavation process, which takes seven to 12 days. The birds take turns flying straight at the riverbank, slamming their pointy beaks into the loam, clay, or sandy soil. A little bit of soil is dislodged with each impact. They keep digging until they've carved out a straight tunnel with an incline up to 30 degrees. It's between 6 and 53 inches deep, which is about 15 to 130 centimeters. The length of the burrow depends on the type of soil it's dug in. At the end of the entrance tunnel is a little nest chamber. Three to ten eggs are laid per clutch, but the typical number is six to seven. The eggs are white, glossy, and more spherical than your typical chicken or songbird egg.

Both sexes incubate the eggs during the day, but only the female incubates them at night. While it's incubating, the parent kingfisher sits facing the tunnel entrance in what one source described as a trance-like state. The incubation period lasts for 19 to 20 days. Typically, one or two eggs per clutch don't hatch at all because the small body of the incubating parent can't keep all of the eggs covered. Kingfishers don't bother lining their nests with nice things like feathers, grass, or moss. Nope. Instead, the floor of the nest chamber is covered by a disgusting accumulation of guano and regurgitated fish and invertebrate parts. It's like a miniature version of a dragon's layer, where the floor of the cave is littered with the discarded bones and

armor of dozens of knights, each of which had the arrogance to think that he could slay the dragon. After that incubation period of about 20 days, the kingfisher eggs hatch, and out pop some ugly little pink dinosaurs. Common kingfisher chicks are altricial, so that means they're featherless, their eyes are closed, and they're basically helpless. And their bills are already quite large. A common kingfisher hatchling looks to me like a cross between a little teradactyl and a gargoyle. The hatchlings stand upright from the first moment, perhaps to minimize the extent that their bodies make contact with the filthy, filthy floor of the nest chamber, and they lean against each other for support. Both mom and dad,

dad feed the chicks. They fly back and forth to the nest all day, bringing small fish to their hungry babies. I'll put a link in the show notes to a lovely little video of a kingfisher family in their nest chamber. About 25 days after they hatched, it's time for the chicks to leave the nest and see the light of day for the first time. They'll still be fed by mom and dad for a few days, but then the carefree days of freeloading are over. The fledglings must start to make their own foraging dives. And this is where life gets really challenging for a young kingfisher. Some of them won't survive their first dives into the water. They get waterlogged and drown. And not long after leaving the nest, the parent kingfishers kick their offspring to the curb. They force the fledglings to leave the

territory. By some estimates, only about half of the recently evicted youngsters will survive their first two weeks of living on their own, and then only half of those survivors will live through their first winter to see the next spring. That's the case for populations in the more northerly temperate regions anyway. So life can be cruel and short for a young common kingfisher. This relatively low survival rate of the juveniles is probably why a breeding pair of adults will often have two or three clutches every year. One in spring, another in early summer, and one in late summer or even early fall. And it's not uncommon for there to be four clutches. In one scientific study, there was this pair of kingfishers in Slovakia that went through five rounds of breeding in a single season.

Over 185 days, the pair successfully raised 19 chicks. And that's from only three of the breeding attempts, since two of them actually failed. Each time the pair began a new breeding attempt before the previous one was even complete. Other common kingfisher pairs have cranked out up to 28 chicks in a single season. Now, that may seem a bit excessive, but you can imagine how this sort of thing is necessary. For a common kingfisher population to maintain a stable size, breeding pairs have to raise a bunch of chicks each year. Otherwise, the low rate of survival in the juveniles would cause the population to crash. Some researchers have pointed out that the common kingfisher nestlings have fairly low energy requirements.

That's because the nest chamber stays at a constant comfortable temperature, and each chick is fed a diet of calorie-rich fish. The parents can raise multiple large broods each year because each of those chicks doesn't cost all that much in terms of the energy the parents need to spend on it. So annual survival in young kingfishers is low, but survival in adults from one year to the next isn't all that great either. The cruel joke might be that by raising so many babies over the spring and summer, the adults can end up exhausted and weak when winter rolls over. round. The most productive adults might be more susceptible to dying from cold or starvation in winter. I'm not sure if there's any scientific evidence for that yet, but it's an interesting hypothesis. In any case, most common kingfishers live only one to four years. But of course,

there are always outliers, those rugged survivors that somehow beat the odds. The oldest recorded common kingfisher, after all, was at least 21 years old, which is amazing. As we wrap up this episode, I'll leave you with the first few lines of the poem, The Kingfisher, written in the early 20th century by the Welsh poet William Henry Davies. It was the rainbow gave thee birth, and left thee all her lovely hues. And as her mother's name was tears, so runs it in my blood to choose for haunts the lonely pools and keep in company with trees that weep. Thanks for hanging out with me today to learn about Al Cido at this.

I look back at my records in eBird, and apparently I've only seen one individual common kingfisher ever. I could have sworn I'd seen more of them. But nope, just one in southern Spain a few years ago. I really hope I get to see this species again and spend some quality time watching its fascinating behaviors. If you dig kingfishers and you'd like to learn more about this species, entire family of birds across the planet, be sure to check out episode 20 of this podcast, which was all about that family. As always, I want to express my deep appreciation for the members of my Patreon community for helping to make this show possible. And welcome to the most recent

batch of cool people to become members. Silken Paw, Corey Osborne, Molly Pesquale, Cynthia Bonds, Ari, Milo Lineman, Katie, Wild Birds Unlimited of Pensacola, and Judith Walker. Thank you all so much for the generous support. Becoming a member is easy. You can check out the details by clicking the support the show link near the bottom of the show notes, or you can just go over to patreon.com slash science of birds. I'm reasonably reachable by email if you have something you'd like to share with me. maybe some gushing praise for the podcast, or a poem about kingfishers, or your tips and tricks for outrunning the cops while you're out birding.

In any case, my email address is Ivan at Scienceofbirds.com. This again is episode 102. You can check out the show notes for the episode, along with some curated photos of common kingfishers, on the Science of Birds website, scienceofbirds.com. I'm Ivan Philipson, and I wish you a fantastic day. Peace.