The Science of Birds - Cuckoos

Episode Date: February 25, 2026

👕 Bird Merch —  Get yourself some bird shirts!~~~In this episode, host Ivan Phillipsen dives into the diverse and sometimes mysterious world of the avian family Cuculidae. While the family is famous for the iconic call of the Common Cuckoo and cultural icons like the Cocoa Puffs mascot, it also includes a wide array of other fascinating birds such as roadrunners, coucals, couas, anis, and malkohas.Learn about the unique biological traits and behaviors that define this cosmopolitan group. From their distinctive zygodactyl feet and plumage variations to their innate, genetically-programmed vocalizations. The episode also highlights the famous behavior of brood parasitism—where some cuckoos leave their young to be raised by other species—as well as the physical adaptations that allow others to thrive as terrestrial sprinters or arboreal skulkers.Links of Interest Striped Cuckoo "jazz hands" foraging [VIDEO]Link to this episode on the Science of Birds websiteSupport the show

Ah, yes, the familiar sound of a cuckoo clock. If you grew up in the 80s, it probably seemed like all the cool kids had a cuckoo clock hanging on their bedroom wall. And of course, I'm talking about the 1880s. These clocks were hand-carved wooden miracles of clockwork technology, literally. It had a tiny mechanical cuckoo bird inside. The cuckoo would pop out of a little door every hour on the hour to jerk its body back and forth while singing its iconic. song. I'm not sure if kids who've grown up in the 21st century are as familiar with Kuku Klox, maybe. But I grew up in the 80s, the 1980s, and Kuku Klox showed up in a lot of old

cartoons. I remember when I first went birding in Europe many years later, and I heard the song of the common kuku for the first time, in real life. I was in Spain, and when I heard that sound, a big grin spread across my face. And the song of the common kuku still, makes me happy every time I hear it. The common cuckoo, Cuculus Canoris, and some of its cuckoo relatives have been culturally significant birds throughout history, from ancient Greek mythology and the plays of Shakespeare to the folklore of India, Japan, and Aboriginal Australia. But perhaps the most culturally significant cuckoo of all time is Sunny. Who you ask? Sonny, the anthropomorphic cartoon mascot of Cocoa Puffs' Serial.

You know, the maniacal orangish-brown creature that looks nothing like a real cuckoo? In countless TV commercials since the 1960s, Sonny has been losing his mind over the prospect of getting to eat some Cocoa Puffs cereal. Sunny is a cuckoo in the sense of being a type of bird, but also in that other sense of the word. Cuckoo, as in a person who is irrational, eccentric, out of touch with reality. Well, today on the Science of Birds podcast, we are going to try not to lose our minds. We're going to stay in touch with reality by learning about the natural history of cuckoos.

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 is episode 129. It's all about birds in the avian family, Ku Kluxi. This family has about 150 species in it. These include the kukus, yes, but also the kukles, Kowls, Kowas, Anis, and Roadrunners. You got that? Kukus, kukles, Kowls, and koohua's. That might be a little confusing if you aren't familiar with these birds.

Hopefully by the end of the episode, you'll have a little better understanding of these different groups. Perhaps. So the family name is Ku Kluxi. You can also pronounce it Kukulidi or Kukulidi. I'm going to try to stick with Kukulidi because that's the pronunciation given by the Merriam-Webster Dictionary. Regardless of how you pronounce it, this is a cosmopolitan family of birds. with species living in many habitats around the world. Besides their associations with wall-mounted timepieces and chocolatey breakfast cereals,

cuckus are famous for being brood parasites. They lay their eggs in the nests of other bird species, and those other birds unwittingly raise the cuckoo chicks. I did an entire podcast episode on this fascinating topic, the topic of brood parasitism. That was episode 12. But here's the thing. Only about one-third of all species in the family Ku-Qulity are brood parasites.

So that breeding behavior is found in a minority of kookus when you look at the entire family. Now, before we dive into the nitty-gritty with these birds, I just want to point out that it was my supporters on Patreon that chose the family Cuculity for this episode. I post polls on Patreon every so often, asking the members of my community there to help me choose a bird family or a bird species or whatever for the top. topic of an episode. The choice for this episode was between cuckus and cowbirds. In the new world, cowbirds are also famous for being brood parasites. Well, cuckus won with 58% of the votes,

while cowbirds got 42. The people have chosen, so let's give them what they want. Let's learn all about birds in the family, Cuculity. Let's start off by looking at the appearance of cuckus. then we'll consider a few of their general behaviors and listen to some of their vocal sounds. Birds in this family are generally medium-sized and they have slender bodies. The classic cuckoo shape, that of the common cuckoo and its close relatives, is an elongated body with a long tail, short legs, and narrow wings. These birds perch in trees and generally live an arboreal lifestyle. But there's another body type found in this family, one that shows a different silhouette.

if you will. Some species that spend most of their time running around on the ground have heavier bodies and longer legs and shorter wings. The two roadrunner species fit that description. But there's also the nine species of ground cuckoos found in three different genera. The ground cuckus and roadrunners are terrestrial birds and their body shapes reflect that lifestyle. These birds can really boogie when they need to. For example, the greater roadrunner can hit speeds of up to 20 miles per hour, or 32 kilometers per hour. Wing shape is longer and narrower in cuckoo species that migrate long distances, and we also tend to find this wing shape in the species that are brood parasites.

And those things are related. Brood parasites tend to be migratory. On the other hand, there are quite a few arboreal cuckoo species that aren't all that great at flying. These include the malcoas and cuckles. They prefer to clamber around in the branches of trees and shrubs, and they often make only short flights. Their wings are relatively short and rounded, which are good for short bursts of flight and for gliding. Almost all species in the family cuculity have a long tail.

This is useful as a rudder in flight, or as a counterbalance in those species that run on the ground. Terrestrial species like the Greater Roadrunner use their long tail for steering, for turning on a dime to catch prey or to escape. predators. A key feature of birds in this family is that their feet are zygadactyl. Remember, a zygadactal foot on a bird has two toes pointing forward and two toes pointing backward. When you see the footprints of a roadrunner, its tracks in the sand or dust, they look like little X's because of the zygadactal toe arrangement. How about the beak, the bill? Bill shape is somewhat variable among members of the cuckoo family, but they all curved downward to some extent. In some species, the bill is kind of short and small. In others, the bill is

long and or thick. For example, onis have distinct bills that are deep and thick, and they have a dorsal ridge. The ridge looks kind of like a fin or a crest. Most cuckoo species have black or dark gray bills, but the 14 or so Malkoa species have more colorful bills. In those birds, the bill is yellow or red orange. And some other cuckookewis species have more colorful bills. And some other cuckookewarm species that are not malcoas also have yellow bills, like the yellow-billed cuckoo here in North America. Considering overall body size, from beak to tail, the teeny-tini-tiniest cuolid cutie is the Little Bronze Cuckoo, Calcetis Minutilis, at 5.9 to 6.3 inches long, which is 15 to 16 centimeters. The specific epithet in the Little Bronze Cuckoo's scientific name, Minutilis, shares its root with the word

you guessed it, minute. The biggest, beefiest species in the family is the channel-billed cuckoo, Sithrop's Novi-Hilandhii. It's 22 to 28 inches long, which is 56 to 70 centimeters. We'll talk more about the channel-billed cuckoo later, but two other species that are almost as big, those are the Goliath cuckle and the greater black cuckle. And the last thing to say about size is that males and females in this family

are usually the same size, so there isn't much sexual dimorphism. But of course, there can be exceptions, and we'll talk about some of those later. Let's look at plumage now. There's quite a bit of color and pattern variation among cuckoo species. Plumages range from subtle and cryptic to bright and elaborate. Females in the parasitic species have the most camouflaged or cryptic plumage. And you can imagine why, I hope. Some species are mostly black or mostly brown or gray.

Rufus colors are seen here and there as well, among the cuckal species, for example. Sunny, the Cocoa Puckoo, as I mentioned, is brownish orange all over. It's kind of an unfortunate color, honestly. And I'm not really sure what species Sunny is supposed to be. Maybe the marketing team at General Mills' cereal company were having a meeting one day, and they got all hyped up when someone showed them photos of the Rufus Cruces. Kukal from the Philippines, Centropus Unirufus. That's really the only species that's brownish orange all over. And hey, what better mascot could there be for cocoa puffs than an obscure

kukulid like centropus unarufus? But if we return to the real-world kukus, we see that iridescent feathers are found in quite a few species, even in the roadrunners. But the most flashy species are the emerald kookus and other members of the genus Chris Ocoxics. Most of these birds are a shade of vibrant green, but one, the violet cuckoo, is a beautiful, dark purple. Many species in this family have white undersides with bold black bars. That's certainly true for the common cuckoo. Males and females in this family look similar in many species. But we do see dichromatism in male and female plumages for some parasitic species in the old world.

For example, that's the case for the emerald cuckus. Females aren't quite so flashy as their male counterparts. Cuckoo feathers are soft in general. They tend to soak up water easily, so these birds can get drenched like a wet dishrag when it rains. To dry their feathers, cuckus will often bask in the sun, and some species, like the onis, will hold their wings out to dry, like a little cormorant or vulture.

The last thing I want to add about the appearance of these birds is regarding the skin on their faces. Many species have brightly colorful bare skin around or behind the eyes. Depending on the species, this could be red, blue, orange, black, or some combination of these. In terms of some basic behaviors in this family, most species are solitary and shy. They keep hidden. Malkoas and cuckles tend to be skilled, skulkers, sneaking around in the shadowy foliage. However, a major exception to this shyness is the three Ani species and their close cousin, the Gwira cuckoo. I think that's how it's pronounced,

Guira, it's G-U-I-R-A. I tried to find a reference for the pronunciation, but I really couldn't find anything. So if you know the proper pronunciation, please shoot me an email. Anyway, these species, the Anis and the Gwira cuckoo, are gregarious. They live and breed in cooperative groups. The sociality of Anis even extends to other species, since they're really chill and trusting around humans and many other animals. Generally speaking, members of the Kuku family are diurnal birds. They're active during the day, but some of them will still call at night. And speaking of calls, let's talk about vocalizations and listen to some of them. These mostly shy birds are often heard more than seen.

Their vocalizations are usually relatively simple. They sound like whistles, flutes, or hiccups. Calls are used to demonstrate territory ownership or attract mates. And I want to point out that the calls of cuckus are innate. In other words, they are not learned. And that's really important, if you think about it, especially for species that are brewed parasites. They lay their eggs in the nests of other species.

If cuckus learned their calls, then they'd end up sounding like. the host birds that raised them. How would they then be able to find other members of their own species, to find a mate? So instead they have genetically programmed vocalizations. They make their species-specific sounds, no matter who their adoptive parents were. All right, here again is the familiar call of the common cuckoo. This one was recorded in France. Next we have another species, the red-chested cuckoo, that's in the same genus as the common. common cuckulus. This red-chested cuckoo was recorded in South Africa.

Heading over to Colombia in South America, we have the charming call of the Pavanine cuckoo. Pavanine, P-A-V-O-N-I-N-E, is an adjective. It means peacock-like, patterned or colored like a peacock's tail. One of the most familiar species in Australia is the fan-tailed cuckoo. Here's the descending call of a fan-tailed cuckoo that was recorded outside of Melbourne. The yellow-billed cuckoo breeds in North America. It's one of the few species you can hear calling north of the Mexican border. But this particular recording of a yellow-billed cuckoo was made in Sonora, Mexico. The co-uas are found in Madagascar.

Co-uah is spelled C-O-U-A. The giant co-uah is a mostly ground-dwelling bird. Here's an example of its loud call. The blue Kowua from Madagascar is a beautiful bird with plumage that's a rich cobalt blue all over. It's an arboreal species. Let's listen to its strident staccato calls. Now if you like cute bird sounds, let me introduce you to the Philippine Kukle, found in, you guessed it, the Philippines. I've got one more for you.

This is the red-billed Malkoa, recorded in Borneo. Now let's get into more stats and factoids about the family cuculity. First, let's consider what other birds are the closest relatives of the cuckus. If we look at the avian tree of life, we find a branch that ornithologists have named otidomorphy. This branch, or what scientists call a clade, is something a bit more inclusive than a taxonomic order. because the clade otididomorphy contains three orders, cuculaformes, musophagiformes, and otidaformis. Each of these orders contains just one family.

Cuculaformis, of course, includes the family Cuculidae. Musifagiformes is the order that contains the Turrico family, musafagody. And finally, the order Otitaformis contains the family of the bustards, Otididi. Now, I know that was a lot of weird scientific terminology with lots of syllables, but the point is that the birds most closely related to the cuckus are the Turricos and Bustards. Turcos are colorful arboreal birds found only in sub-Saharan Africa. They're really beautiful, and a lot of them have really cool crest feathers. Bustards are mostly large terrestrial birds, and they're found in Africa, Eurasia and Australasia.

So now returning to looking at just the family, Cuculidi, if we look at the branches, the distinct evolutionary lineages or clades within that family, we find there are five sub-families. As far as I know, that's what is currently accepted among ornithologists. Okay, so here we go. These are the five sub-families within the family Cuculity. One, Crotafagini. This one includes the Gwira Cuckoo and those three onis.

The Guira cuckoo is white with brown streaks and a shaggy, messy-looking crest. The three ony species have all black plumage, more or less, and distinct really thick bills. Okay, so that was crotaphagony. The next subfamily, number two, is neomorphony. This is a new world group, and it includes the roadrunners and the ground kookos of the new world, 11 species in total. Most of these are terrestrial, but a few of them are arboreal. Subfamily number three is centropodony,

and this includes the 28 cuckal species in the genus Centropus. Cucles are relatively large, heavy-bodied cuckus with long, broad tails and short, rounded wings. They typically show a distinctive color contrast between an overall dark plumage on their body and their chestnut brown wings. Their strong, slightly curved bills and sturdy legs reflect a primarily terrestrial lifestyle.

As they're running around and hopping through the foliage, they hold their bodies and tails stretched out horizontally. They look almost like weird reptiles, like large lizards. Okay, so that was central podani, the cuckles. Then we have cooony. This is the fourth subfamily, and it includes the 10 cooas of Madagascar, as well as the old world ground kookus. So that's 13 species in total. All species in the genus

Kauua are defined by a striking patch of brightly colored bear's skin around their eyes, which is typically a vivid blue or purplish. This facial ornamentation is one feature that distinguishes ko'uas from most other members of the family. There are three species of arboreal ko'uas, and they have feathery crests on their heads. The subfamily ko'o'oan also includes the three species of old world ground cuckus. These are large, heavy-bodied birds with thick bills and nicely patterned plumage. They too have some colorful bare skin around the eyes. And the fifth subfamily is cuckulini, and that includes all the rest, all the typical cuckus, the malcoas, and the coals. All in all, there are 154 species in the family Cuculity,

and those are divided into 25 genera. Of those genera, of those genera, the ones that are most diverse that have the most species are centropus, which has 28 species, and those are all the cuckles. And then we have coxinus, which includes the 13 New World species, including the yellow-build, black-billed, and mangrove cuckus found in the U.S. And then we have the genus Chryso-Coxics with 13 species, and recall that those are the colorful little buggers, the emerald cuckus, the violet cuckoo, and their close relatives. And then we have Cuculus with 11 species. That includes the common cuckoo, Cuculus Canoris. I want to mention just one recent taxonomic change that happened in the cuckoo family.

There was this sweeping change in the 2024 update to the Clements checklist of birds, and that was the breakup of the genus Chrysocoxics. Before that, almost all bronze cuckus were placed in the genus Chrysococoxics. Now that genus is restricted primarily to African-Coxics. species, so like the African emerald cuckoo. The Indo-Pacific and Australian species have been moved to the genus Calcatees. So for example, the little bronze cuckoo, the teeny tini-tiniest species I mentioned earlier, is now calcatees mynutilis, but it used to be Chris Ocoxix's minutilis. Okay, now let's talk geography. How much of the earth's land surface is crawling with cuckus?

Well, remember that this is a cosmopolitan family. That means there are cuckus just about everywhere on all the continents. Well, all the continents, that is, except for the one where few birds dare to tread. I speak, of course, of Antarctica. That ancient lovecraftian waste world of wind-scoured ice. It looms like a vast frozen necropolis, where the very stars seem alien and howling gale's harmonize with the rhythmic chanting of malicious entities who have slumbered beneath the glaciers since eons before the rise of man or bird. In other words, Antarctica has zero cuckoos. Surprise,

surprise. Also, not surprising is the fact that there's more species diversity for cuckus in the tropical latitudes. But there are some geographic regions where cuckoo diversity is especially low, not including Antarctica. These include the southwest of south-west of south America, the far north or northwest of North America, and the driest areas of the Middle East and North Africa. I happen to live in such a black hole of cuckoolessness, because sadly we don't have any cuckulid species in the Pacific Northwest, for some reason. Now, looking at the way that cuckoo diversity is distributed across the continents, in North America we have 26 to 28 species, And the most commonly reported are roadrunner, the greater roadrunner, groove-build ani, and yellow-billed kuku.

South America has 23 species, and the most commonly reported there are the smooth-billed-a-kou, and common squirrel kuku. Europe has just three, three species plus a couple vagrants. By far the most common is the common kuku. And then there's the great spotted kuku, and much more rare is the oriental kuku. Africa has 38 cuckoo species, as long as you can include Madagascar. The most commonly observed species there are Birchel's cuckle, Diderick cuckoo, and white-browed cuckle. Asia wins the prize for the most cuckus. It has 67 to 70 species.

The most common species are Asian coal, greater cuckle, and common cuckoo. And finally, in Australasia, there are 36 species, with the most common being fanned-tailed cuckoo, Pacific Coal and Fessent Coochle. Weirdo alert. Weirdo alert. Uh-oh, it looks like we have a weirdo in the family Cuculidae. It's a bird that we can't just pretend like it's normal and hope that nobody notices that something isn't quite right with it.

Now, I would have said that the greater roadrunner is the best candidate for getting a weirdo alert. Hands down. But, as you might know, I already did an entire. podcast episode on that species and its close relative, the lesser roadrunner. So instead, the honor of being today's weirdo goes to none other than the channel-billed kuku, Sithrop's Novi-Halandi. Remember that this is the largest species in the family. This bird is a partially migratory species. Its breeding range runs across the Indonesian islands of Sulawesi, Buru, and Flores, as well as northern and eastern Australia. It also shows up

in Tasmania and even New Zealand on a rare occasions. The second part of this cuckoo's scientific name, Novi-Holandhi refers to New Holland, which is an old historical name for Australia. During the winter months, channel-billed cuckus in the migratory populations of Australia migrate north to islands in the Malay archipelago, including New Guinea. The habitat of this species is the canopies of tall trees at forest edges or along rivers and in open woodlands. and has a strong preference for areas with lots of figs. Channel-billed cuckus are typically found in lowland, sub-humid, and semi-arid regions, including coastal islands and areas inland away from mangroves.

Its extreme size is just one weird thing about the channel-build cuckoo. But there's more. It has the largest, most massive bill of any cuckoo, relative to the size of its head and body. This beast looks more like a hornbill or a toucan than a cuckoo. In fact, the only other bird with the word channel in its name is the channel-billed toucan. Coincidence? Probably. Channel refers to a deep groove running along the cuckoo's bill, lengthwise from the base toward the tip.

The bill has a downward curve. It's a dark-modeled gray at the base with the distal third towards the tip being cream or bone-colored. The plumage overall is gray, with darker spots on the wing feathers. Then the tail has bold black and white markings. The channel-billed cuckoo is a fierce-looking bird, because of that massive bill, yes, but also because the irises in its eyes are blood red. And the bare skin encircling the eyes and the base of the bill is also red. This weirdo stands alone.

It's the only species in the genus Sithropes. And that's my best guess at the pronunciation, Sithrops. It's spelled S-C-Y-T-H-R-O-P-S. Even this genus name sounds wicked, doesn't it? It comes from ancient Greek and combines the words Scrutos, meaning angry, and opos, meaning face. So Sithrop's means angry face. You know, because of the red eyes, red facial skin, and the massive hooked bill. So what does this big old angry-faced cuckoo sound like? Well, luckily I found a great recording for you. It was made in Indonesia on the island of New Guinea.

To some Aboriginal people in Australia, this cuckoo is a key character in stories having to do with the arrival of rain. They have names for it like storm bird, rain bird, or floodbird. This is because the channel-billed cuckoo's migratory return to northern Australia coincides with the beginning of the rainy season in August and September. The bird is, like many cuckus, rather shy. So it's heard more often than seen, and its loud, raucous calling from the tree canopy is a signal of its presence during the change in season.

That last recording there was made just north of Sydney, Australia. Besides the channel-billed cuckoo's making a racket in that recording, you can also hear the Pacific Coal, another cuculid species, as well as noisy miners and little corolla's. In terms of diet, the channel-billed stormbird is primarily frugivorous. In other words, it's a fruit eater, which is unusual among birds in the cuckoo family. It has a strong preference for figs and for mistletoe fruits that it finds in the forest canopy. But it also consumes insects and occasionally the eggs or nestlings of other birds.

And speaking of the nestlings of other birds, in case you were wondering, yes, the channel-built cuckoo is a brood parasite. It's the world's largest brood parasite, to be exact. It primarily targets the nests of large passerine birds such as crows and other corvids, curawongs, and magpies. To execute their sneaky egg-laying plan, breeding pairs of channel-build cuckus often cooperate. The male distracts the host birds by provoking a mobbing response from them. He gets them all riled up while the female slips into the host nest to lay her egg. Unlike many other cuckoo species, the channel-build cuckoo chicks might not

actively eject the host eggs or chicks. But the parasite chicks often monopolize the food supply to the point where the host's offspring rarely survive. So there you go, the channel build kuku, a weird, angry-looking brood parasite that's a herald of the rainy season, and it likes to eat figs. Let's talk about migratory behavior in the family Kukulidi. The channel-build kuku is an example of a partial migrant. Some of its populations migrate with the seasons, and other populations are resident or sedentary. Most species in the family Cuculity are sedentary, meaning they occupy the same region all year long. But other species are regular seasonal migrants. The common cuckoo, for example, is a long-distance, complete migrant. Every individual in the species migrates. Common cuckoo's breeding in

Europe, for example, migrate south in autumn to Central Africa. Their journey takes them nonstop over the Mediterranean Sea and Sahara Desert. And do you remember that there were those individual common cuckus that researchers tracked as they migrated from China to India and Africa? I talked about them way back in episode four of the podcast, which was all about migration. The two cuckoos were named Skybomb Bolt and Flappy McFlapperson. Remember them? Good stuff. Anyway, yellow-billed and black-billed cuckus migrate from North America, where they breed, to South America in the winter. Their migratory journeys take them on non-stop flights over the Caribbean Sea. Another amazing example is the long-tailed coal, Eurodynamus titensis.

This migratory species breeds in New Zealand during the spring and summer, and then it spends the winter months on Polynesian islands far to the north. An average one-way journey from New Zealand to Polynesia is approximately 1,800 miles or 3,000 kilometers. So the resulting round trip is over 3,700 miles, which is 6,000 kilometers. Some cuckoo species are more nomadic. They move in response to environmental conditions over relatively short intra-continental distances. And some cuckus are altitudinal migrants, meaning they move up and down in LLU. elevation with seasons, so in the vertical dimension, more so than the horizontal dimension.

Birds in the family cuculity are found across a wide spectrum of habitat types, from evergreen rainforests and woodlands to mangrove forests, scrub, and even deserts. Cuckus are found from sea level to over 14,000 feet, which is about 4,000 meters. Most species make their homes in forests or woodlands. They are especially abundant in in tropical rainforests. Some species, however, are at home in drier, more open country. The two roadrunner species are great examples. But there's also the pallid cuckoo in Australia.

It's found across the continent, even in the desert interior. Just to give some specific examples of habitat use, let's consider three species, the common cuckoo from Eurasia, the yellow-billed cuckoo of the Americas, and the fanned-tailed cuckoo in Australia. The common kuku lives in a diverse range of environments across Europe and Asia, including open woodlands, forest edges, marshes, and reed beds.

These birds prefer landscapes that have some open ground for foraging on insects, as well as some elevated perching sites for scoping out the nests of their host species. During the winter, common kukus migrate to tropical regions in Africa and Southeast Asia, where they occupy similar forest edge and savanna habitats. The yellow-billed cuckoo primarily breeds in deciduous woodlands, as well as open forests with dense shrubby undergrowth and riparian corridors across North America. These birds prefer habitats near water sources,

such as river valleys and marshes, where they can find abundant prey and thick vegetation for nesting. In the winter, they migrate to South America, occupying tropical scrub, forest edges, and mangrove habitats. And as a final example, we have the fan-tailed cuckoo. This bird occupies a broad range of habitats across Australia and New Guinea, including temperate and tropical forests, woodlands, scrublands, and mangroves. It's particularly common in open woodlands, forests, forest edges, and roadside,

where it can easily locate the nests of its host species. Now it's time to look into the past at the evolution of the family cuculity. Remember that there's a clade called otidomorphy. It includes the cuckus along with busters and turakos. Well, molecular genetic data from DNA, using the dating technique called the molecular clock, that tells us that the otidomorphy clade

originated approximately 50 to 60 million years ago during the Paleocene or Eocene epoch. And then maybe five to ten million years later, the cuckus evolved and ended up as their own distinct evolutionary lineage, the family cuckulity. Molecular evidence from DNA also suggests that obligate brood parasitism evolved independently on three separate occasions in the history of the cuckoo family. Remember that only about one-third of the species in the family are brood parasites. The idea that brood parasitism evolved three times in the family is supported by the fact that a single

origin for parasitism would require parental care to have been lost and then re-evolved a bunch of times. That would be a violation of Dolos law. This law states that evolution is basically irreversible, meaning that once a lineage of organisms has lost, through evolution, a complex structure, physiological trait or behavior, it's highly unlikely to be regained in its original form. This occurs because the specific sequence of genetic mutations and environmental pressures that created the trait in the first place is statistically improbable to repeat exactly. So that's Dolo's law.

In the case of cuckus, it's far more likely that their ancestor was a species that took care of its own chicks. it wasn't a parasite. Then parasitism evolved independently in three different cuckoo lineages. That's more likely than the alternative scenario where the common ancestor was a parasite. If that was the case,

non-parasitic parental behavior would have re-evolved in a bunch of lineages and then three of those lineages would have re-evolved, yet again, reverting back to being parasitic. So the most reasonable, most parsimonious explanation is that the common ancestor was not a parasite, and that brood parasitism evolved independently

three times in the cuckoo family. The first evolutionary event occurred within the New World Ground cuckus, which make up the subfamily neomorphony. Only a few species in this subfamily, like the striped cuckoo, became parasitic, but their closest relatives, such as roadrunners, remain parental. The second distinct lineage is represented by the crested cuckoo's in the genus Clamator. Their chicks outgrow rather than evict their host nestmates. The third and arguably most successful invention of parasitism occurred in the true old-world cuckus, birds in the sub-family Cucullin. This is a massive evolutionary radiation of over 50 species. Their chicks possess the specialized, instinctual and brutally effective behavior of physically evicting

host eggs and or young from the nest. And this leaves us with a question, I think. What is it about cuckus that made it more likely for them to evolve into brood parasites compared to birds in most other families? Because it happened three times, independently, right? One of the leading hypotheses is this. First, some ancestral cuckus expanded from tropical forests into more open, seasonal habitats. which led to changes in diet, increased breeding range, size, and the development of migration.

Brood parasitism then evolved as a subsequent adaptation to reduce the heavy energy demands of reproduction. If you can let someone else raise your kids, you have more energy to spare, and so you're more likely to survive your long migratory journeys. That's the idea anyway. But now I'm wondering, if this is all how it really played out for cuckoos, Why didn't brute parasitism evolve in a lot more migratory bird species across a bunch of other families? Something to ponder, I guess. But let's move on.

Here's another crazy cool thing about cuckoo evolution. Many parasitic cuckus, like the common cuckoo and its close relatives, use what biologists call Batesian mimicry to resemble predatory hawks, like sparrowhawks, gosshawks, or excipiters. The cuckus have features like gray backs, barred underparts, yellow eyes, and a flight silhouette that looks a lot like a small hawk. There are even eight species in the genus hierocoxics that are called hawkookos. There's the northern hawk cuckoo, Malaysian hawk cuckoo, and so on. And wow, they really do look like little raptors.

This evolutionary convergence allows cuckus to get access to host nests by frightening parental birds away or deterring them from mobbing. It's like a cuckoo swoops in, lands on a branch, and says to the host parents, Rar, I'm a spooky hawk. You better get out of here or I'm going to eat you. Seriously, as you can clearly see from the barring on my belly, I am definitely a hawk and not a cuckoo. So yeah, scram already. Save yourselves and leave your nest undefended. The host parents oblige and then the female cuckoo sneaks in to lay her egg. Okay, let's go ahead now and talk about the conservation situation for cuckus.

Considering the IUCN Red List categories, four species are in the near-threatened category, eight are vulnerable, and three are endangered. And the three endangered species are the Sumatran ground cuckoo, coral-billed ground cuckoo, and the bay-breasted cuckoo. I was just in the Dominican Republic on the island of Hispaniola, and I had a chance to see the bay-breasted cuckoo, because that's where it's endemic to, and I didn't see it, I missed it.

But some of my friends saw it. Bummer. I mean, good for them, but bummer for me. And bummer for the bay-breasted cuckoo, because it's endangered. Now, there's one species that is in the critically endangered category, and that's the black-hooded cuckol, Centropus Styri-E.

It's also known as the Mindoro Cucle. This is one of the rarest cuckoo species in the world. It's endemic to the island of Mindoro in the Philippines, where its population is extremely small and severely fragmented. The primary threat to its survival is the extensive loss of its lowland forest habitat due to deforestation and land conversion. Habitat destruction, like what's happening to the black-hooded cuckol, is the primary threat to cuckus in general.

It's especially bad in Southeast Asia. Other major threats to cuckus include opportunities, hunting for food, introduction of non-native competitors, and predation by introduced non-native mammals. There are two species in the family Cucullity that were driven to extinction by humans. The snail-eating co-uwa was endemic to the island of Nozibaraha, off the coast of Madagascar. And yes, it seems to have specialized in eating snails on the forest floor. Big snails. The snail-eating co-uah would crack a snail shell open by,

smashing its prey in a rock. The last confirmed specimen of this bird was collected in 1834, and although there were unconfirmed sightings reported into the early 20th century, the species is now officially considered extinct. Its demise was primarily caused by the complete deforestation of its native island habitat, possibly in addition to hunting for its feathers or meat, and predation by introduced rats was also a major factor. The second extinct species is the St. Helena Cuckoo, Nanocoxics 6. 6 is spelled P-S-I-X. It was endemic to the island of St. Helena, way out in the middle of the South Atlantic Ocean.

This species is known only from its bones, specifically a humorous from the wing, which suggests it was a relatively small bird. The extinction of the St. Helena Cuckoo probably occurred shortly after the island's discovery in 1502. In a sad situation that closely paralleled the fate of the snail-eating cuckoo, the St. Helena Cuckoo suffered from the complete deforestation of its native habitat, and perhaps also because of invasive predators like rats, cats, and dogs. Because it disappeared so quickly after human arrival, no records of the living bird exist.

It belonged to the subfamily cucullinni, and it's currently the only known species in the genus Nanocoxic. Remember that one of the many things that makes the channel-billed cuckoo a weirdo in its family is that it eats mostly fruit? Well, that's because the more typical cuckus eat insects. In fact, they tend to specialize in eating large insects, especially caterpillars. They even eat the hairy, spiky, noxious caterpillar species that most other birds avoid like the plague. Or avoid like I'd avoid an Arby's fast food restaurant. Noxious indeed.

When a cuckoo snatches up a fat, hairy caterpillar, the bird will often process its prey before eating it. It holds the caterpillar in its beak and rubs it back and forth on a tree branch or other hard surface. This helps to rub off some of those nasty hairs or spines. Caterpillar munching cuckus also have an anatomical adaptation for dealing with their somewhat unpalatable prey. Many cuckoo species have a specialized stomach lining. It's tough and protective, so it can handle the irritating or even toxic hairs of noxious caterpillars. Instead of injuring the bird, the sharp hairs pierced the protective stomach lining, so the actual stomach wall is shielded from damage.

To prevent a dangerous accumulation of these materials, the cuckoo has a sloughing mechanism, where it periodically sheds the entire stomach lining and then hacks it up. It regurgitates it as a pellet, clearing the digestive tract of all that, hazardous caterpillar debris. Some members of the cuckoo family eat more than just insects. Some of the larger species like cuckles and most of the ground dwellers like roadrunners will eat small vertebrate prey as well. We're talking rodents, birds, snakes, and lizards. There's even a group of species in the Caribbean islands called the lizard cuckus. For example, there's the Jamaican lizard cuckoo, Puerto Rican lizard cuckoo, and Hispaniolan lizard cuckoo. Now that one, I did see

when I was in Dominican Republic, the Hispaniolan lizard cuckoo, which is also endemic to that island. These lizard cuckus, true to their names, specialize in eating arboreal lizards like the annoles. I want to highlight the foraging behaviors of a couple new world cuckoo species. In northeastern Peru and the Amazon basin, the red-billed ground cuckoo, neomorphous puturanii, has a special relationship with two species of monkeys. The monkeys are adorable little tamarins, the brown mantled and the mustached tamarin. This association benefits the ground cuckoo because it loiteres around on the forest floor beneath the monkeys as they feed in the canopy. The silly monkeys drop some of their half-eaten or discarded fruit.

Waiting down below, the red-billed ground cuckoo pounces on the fruit and it gets an easy meal. This relationship is a classic example of what biologists call commensalism. This is a type of symbiosis where one species benefits, while the other is neither significantly helped nor harmed. The ground cuckoo benefits, and the monkeys aren't really affected either way. Then we have the striped cuckoo, Taperna nivia. This species lives in central in South America. It's a streaky, modeled brown bird with a long tail and a short bill, well, short for a cuckoo. This bird has become a little bit of a social media superstar because of its unusual foraging behavior. Videos of it have gone viral because they're pretty funny.

While foraging on the ground in open habitats, the striped cuckoo holds its head steady while jerking its little body left and right. It has what look like hands sticking out from the leading edges of its folded wings. Some people describe them as jazz hands. They're not hands, but they're actually blunt black feathers. They're part of the alula, the collection of flight feathers associated with what is essentially the bird's thumb. The striped cuckoo looks like it's doing a little dance, jerking back and forth with its jazz hands flashing. The bird moves forward with stuttering motion. The idea is that those flashing alula feathers might spook any insects in the leaf litter,

causing them to move and reveal themselves to the hungry cuckoo. I'll put a link to a video of the dancing striped cuckoo, And if you haven't seen it before, you're going to love it. When it comes to breeding, birds in the cuckoo family show a wide range of behaviors, including monogamy, cooperative breeding, and of course brood parasitism. And that's what they're most famous for. For the species that aren't parasitic, which is most of them, they tend to be monogamous. And that's true for birds like roadrunners and malcoas.

The three oni species and Gwira cuckoo live in communities. groups. In the group, there are still some monogamous pairs, at least in the case of the Anis. But genetic evidence suggests Anis may also dabble with polygamy and other deviations from monogamy. And just for fun, here's the sound of the groove-build Ani, recorded in Ecuador. Guiracuckus are polygenandrus. That means multiple males and multiple females mate with one another within a single breeding season. And they share nesting duties. in their communal nest, which can have up to 20 eggs in it. Interestingly, the Guirakuku represents the most ancient lineage within the family

Kuulity, followed by the Anis. Another interesting thing related to breeding is that the roles of the sexes are reversed in the cuckles. These are the 28 species in the genus Centropus. Unlike most birds, where females typically provide the majority of parental care, male cuckles are the primary caregiver. They're responsible for nest building, incubation, and feeding the young. This reversal is also reflected in their physical appearance, as all cuckal species show reversed sexual-sized dimorphism,

where the females are larger than the males. Now, as for brood parasitism, let me again remind you that there's a podcast episode I dedicated to that topic. It was episode 12. So check that out if you want to learn more about this fascinating behavior. But I do want to point out that among species in the family cuculity, many are not at all parasitic, while some are obligate parasites, and others are facultative parasites. Obligate means they always do it. They have no choice but to be brood parasites.

Facultative, on the other hand, means they act like parasites only sometimes, under certain conditions. For example, the yellow-billed cuckoo and its close relative, the black-billed cuckoo, are facultative interspecific brood parasites among altricial birds. They've been observed taking advantage of at least 11 passerine species as hosts, including the American Robin, gray catbird, and woodthrush. Yellow-billed cuckus even parasitized the nests of black-billed cuckus, sometimes. So yeah, sometimes the parasite becomes the host. It gets a take-a-old cuckus even parasitizes. It gets a of its own medicine, no honor among thieves, and so on. But again, the yellow-billed and black-billed cuckus are facultative brood parasites. They often just build a nest and raise their own chicks like

honest, hard-working birds. The trigger to break bad and lay your eggs in someone else's nest for these species might be an abundance of food in a particular breeding season. When the land is overflowing with juicy caterpillars or cicadas, a female cuckoo might crank out more eggs than she can possibly raise herself. So she drops some of them into the nests of nearby host species. In the new world, there are only three cuckoo species that are obligate brood parasites. They make up that lineage we talked about, the subfamily neomorphony, or at least they're part of that subfamily. That was one of the three instances of brood parasitism evolving in this family. and the striped cuckoo with its jerky little jazz hands,

that's one of the new world obligate brood parasites. Brood parasitic cuckus show a range of associations with their host species, varying from extreme specialization to broader generalism. In many highly specialized species, like the common cuckoo, the species is divided into distinct host races known as gentis, spelled G-E-N-T-E-S. Each gens, that's the singular form, targets a specific host species

and has evolved eggs that remarkably mimic the color, size, and pattern of that host's eggs. This specialization is a critical adaptation that decreases the likelihood of the host detecting and rejecting the parasitic egg. So within the common cuckoo, there are these different gentees

associated with different host species. It's amazing stuff, right? The broad pattern we see in these evolutionary associations between parasite and host is a continuous arms race or co-evolutionary cycle. As the host species evolve more sophisticated defenses, like the ability to recognize subtle differences in egg appearance or increased aggression toward adult cuckoos, the parasites face intense natural selection,

so they up their game. They get better at mimicry and better at being sneaky little buggers. This feedback loop often results in highly specific and localized adaptations where the cuckoo's success depends entirely on its ability to stay one step ahead of a particular host's defenses. In whatever nest they hatch from, all cuckoo chicks are altricial. They're mostly helpless, blind, and they have naked, translucent skin. And I say mostly helpless because many of the brood parasite chicks start pushing and shoving the host eggs and chicks in their nest right away. They muscle the eggs or chicks out of the nest over the side to fall to their death.

Parasitic chicks also grow faster than the host chicks, and they beg more loudly and vigorously to monopolize the food. Some cuckoo chicks have a disgusting superpower. If a predator, like a bird of prey or cat comes poking around the nest, the chicks can blast out a stinky liquid from their cloacas. The baby cuckoo shoots this dark, malodorous secretion in the general direction of the predator. And the intense stench is often bad enough that the predator's like, oh, hey, no, no, I'm out of here, got to go. I don't want any of this. This stinky projectile liquid is a complex mixture of volatile compounds, including acids and acids.

sulfur-containing molecules. And it appears that some of these are especially repulsive to mammalian olfactory systems. Once a cuckoo chick has fledged and it's off on its own, it might survive four to ten years in the wild. Regarding lifespan, there's an interesting trade-off related to the breeding strategies we discussed earlier. So for parental cuckus, the ones that take care of their own chicks, these species have to deal with the physical wear and tear of building nests and feeding multiple hungry chicks. But on the other hand, these same species are often non-migratory, which removes the massive survival risk of crossing vast oceans or deserts.

But in those parasitic cuckus, the adults are freed from the energy-draining task of parenting, which theoretically should extend their lives. However, many of these species are long-distance migrants. For a common cuckoo, for example, the risk of dying during a journey across the Sahara Desert is much higher than the risk of dying while raising a chick. And remember that a migratory lifestyle seems to have been one of the preconditions or pre-adaptations for brood parasitism to evolve on three separate occasions in this family. I guess my own life is more like the brood parasites that migrate long distances. I don't have any kids and I travel a lot, so how's that going to affect my lifespan?

Who knows? Time will tell. Anyway, now I'm wondering about cuckoo species that are both parental, in other words, non-parasitic, and long-distance migrants. Shouldn't those birds be burning lots of energy and having the maximum amount of wear and tear, such that they flame out pretty quick, that they have short lifespans? Well, we can look again at the yellow-billed and black-billed cuckus. They migrate long distances and often raise their own broods. From what little data we have, or what I could find,

it seems these cuckus live for only about four to five years. And that does seem to be on the short end of the distribution for birds in the family cuckulity. Interestingly, the yellow-billed cuckoo goes from hatching to being fully fledged in just 17 days. The chicks grow insanely fast. In fact, this is one of the fastest development periods, not just for a cuckoo, but for any bird species. Cuckus are a diverse, widespread group of amazing birds. They've taken several different evolutionary paths with some fascinating adaptations.

Communal nesting, tree-dwelling versus ground-dwelling lifestyles, caterpillar-proof stomachs, foraging with jazz hands and brood parasitism that has evolved more than once. I hope that after listening to this episode that you are cuckoo, not so much for cocoa puffs, but for the cuckus themselves. That is a wrap on episode 129 and on the family Cuculity. For now. As always, there's more we could talk about with this group of birds, but I think we covered a lot of the most important and interesting stuff. As always, a massive thank you to all my once. wonderful supporters on Patreon. I deeply appreciate your help in making this podcast possible. My newest patrons are Justin Mary, Caitlin, Thomas Hayden, Sandra in Ohio, Jace, Jeremy Prendiville,

Donna Jean, Gina P., Calliatt T. Valsaraj, Virginia Johnson, Livermouse, Fran Tolar, Monica J. Mead, Marcy, Kelly Schart, Nancy C., and Matthew Carnes. Welcome to all of you and thank you. you so much for joining the community. And please forgive me if I have mispronounced your name. If you are not a part of the community yet and you're thinking about joining, you can check out my Patreon page over at patreon.com slash science of birds. And if you have something you'd like to share with me, please go ahead and shoot me an email. My address is Ivan at scienceofbirds.com. Maybe you have a comment about the podcast, or you want to describe the kind of interpretive, jazz, or hip-hop dance that you use when foraging for food.

For me, I like to do the running man when I'm searching for frozen mozzarella sticks at the grocery store. Works every time. Again, this is episode 129. You can check out the show notes for the episode along with some photos of the lovely cuckoos I talked about today on the Science of Birds website, Scienceof Birds.com. And hey, don't forget to check out bird merch,

my online store over at birdmerch.com. As always, I am Ivan Philipson, and true fact about me, I love reading fantasy and science fiction novels. Tolkien and Asimov are longtime favorites, but more recently I've loved the Expans series by James S.A. Corey, the Babaverse series by Dennis E. Taylor, and a bunch of books by Adrian Chikovsky, including his Children of Time series. I just love speculative fiction in general. That's my favorite genre for movies as well. Anyway, thanks for listening and thanks for wanting to learn more about birds. I'll catch you later. Cheers.