The Science of Birds - Pigeons and Doves

Episode Date: July 30, 2021

This episode is all about birds in the family Columbidae. These are all the world’s many species of pigeons and doves.These birds are more exotic and interesting than many of us give them credit for. This is a widespread, diverse group that has been around for many millions of years. Pigeons and doves occupy many habitats across the planet, and they’ve colonized countless remote islands. Many of them are as richly colorful as parrots or songbirds.~~ Leave me a review using Podchaser ~~~~ Become a patron to support the podcast ~~Link to this episode on the Science of Birds websiteSupport the show

In ye olden days, in the Middle Ages, European medicine revolved around the study of the four humors, blood, phleg, yellow bile, and black bile. A person's health was said to depend on the balance or imbalance of these four fluids in the body. The four humors were also believed to influence a person's mood or personality. If, say, you had too much black, bile in your guts, you were likely to be gloomy and depressed, and just sort of a bummer to be around. Like Eeyore or Professor Snape, or like anyone who doesn't listen to podcasts about birds. An excess of blood, on the other hand, would make you a happy, optimistic person, and so on. During roughly the same historical period, medieval naturalists made an astonishing discovery

about the internal anatomy of pigeons and doves. It turns out that these birds do not have a gallbladder. It's true. Pigeons and doves do not have a gallbladder. The gallbladder is a little storage sack for bile. Also known as gall, bile is a greenish or yellowish secretion that helps with the breakdown and digestion of fat. Humans have a gallbladder, of course, as do a bunch of other animals. Medieval doctors identified the gallbladder as the source of yellow bile, one of those four humors.

It was thought that when somebody's body has too much yellow bile, it makes them short-tempered and violent. So those naturalists in the dark ages ended up connecting the dots. They reasoned that because pigeons and doves have no gallbladder, they must produce no yellow bile. and a lack of yellow bile would explain why these birds have such gentle, timid dispositions. To paraphrase a 13th-century monk named Bartholomeus Anglicus, The dove is a messenger of peace, an example of simpleness, clean of kind, plenteous in children, follower of meekness, friend of company, and a forgetter of wrongs. And here's a quote from a medieval bestiary.

quote, the dove lacks gall and nests in holes in rocks. It does not eat corpses or live by plunder, but instead gathers the best seeds. When menaced by a dragon, doves will fly to a peridexian tree, where they are safe. End quote. Ah, medieval science. It was only a matter of time before a dragon came into the picture, wasn't it? Anyway, it turns out that pigeons and doves actually do produce bile. It's secreted by the bird's liver and drips directly into the small intestine. So, while it's not really true that the dove lacks gall, it is true that they don't usually eat corpses. And I think most of us would agree that these birds really do come across as gentle-hearted, passive creatures. But enough of all this misguided medieval medicine and

silliness about dragons. Let's get real and learn about the biology of pigeons. and doves. Hello and welcome. This is the Science of Birds. I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted, guided exploration of bird biology for lifelong learners. This episode is all about birds in the family.

family, Columbody. These are all the world's many species of pigeons and doves. An important side note here is that it was my patrons who helped me decide which bird family to feature in this episode. A while back, I put out a poll to my supporters on Patreon, asking them to choose from among several families. Columbadie was the clear winner at first, and I thought the poll was complete, so I called it. The pigeons win! However, this being my first, Patreon poll, I had forgotten to set an end date for it, so new patrons kept adding their votes. Eventually, all three of the families I offered as choices ended up with an equal number of votes. But I had already announced the winner, however prematurely, and so here we are. Pigeons

and Doves! But seriously, thank you to all my patrons who voted. I appreciate the participation and look forward to running more polls to get your help in selecting topics for episodes. Now back to the topic at hand. Maybe you hear the word pigeon, and what pops into your mind is an image of a ubiquitous, gray-colored city bird that some might call a flying rat. You picture the pigeons strutting around on a dirty sidewalk, pecking at the crumbs of a hot dog bun, or maybe a lighting upon a statue to decorate it with a dollop of guano. If that's one of the few impressions you have of pigeons, I'd say you aren't alone. Whether you love them or hate them, the feral pigeons that share our cities represent one of the most familiar bird species on the planet. But there are so many other things going on with this diverse family of birds.

Pigeons and doves are more exotic and more interesting than many of us give them credit for. So let's see if we can expand our minds today by learning about and appreciating the wonderful birds in the family, Columbidy. What are the key traits of birds in the family columbody? Body shape is remarkably consistent across the many species of doves and pigeons. Picture your typical city pigeon, and there you go. Their bodies are plump and ovoid, or egg-shaped. They have small, round heads sitting on top of thick necks. Most species are medium-sized birds, more or less the size of a city pigeon.

But the smaller species in this family are no bigger than a sparrow. These little birds include the dwarf fruit dove, telinopus nina, and the common ground dove, columbina passerina. They're about six to seven inches long, or 14 to 17 centimeters. Sheep makers' crowned pigeon, Gora sheep makeri, is probably the largest member of the family at up to 31 inches or 79 centimeters long. This huge pigeon and the dwarf fruit pigeon both live on the island of New Guinea. The shape of the bill is also pretty consistent among the world's pigeons and doves. It's short and slim. Many species have a fleshy or waxy lump of

skin that covers the base of the bill. This structure is called a seer, C-E-R-E. In some species, the sear is larger and or more colorful. These birds are strong, fast flyers. Their wings are relatively large and roughly oval-shaped, or elliptical. This elliptical wing shape provides high maneuverability and the ability to launch into the air quickly, pretty useful for avoiding the teeth or talons of pouncing predators.

When it comes to plumage colors and patterns, birds in the family Columbidee are often some shapes, of gray or brown. Barring and spots are common embellishments, especially on the wings. Many species sport patches of iridescent feathers. Now there isn't much sexual dimorphism in this group. Male doves and pigeons tend to look more or less the same as their female counterparts. Now if you think gray or brown colored birds are boring, I'm sorry to hear that, but I'm also happy to tell you that there are dozens of species that are more brightly colored. Most of these are some shade of green, while a few are bluish overall. The fruit doves win the award for the most colorful

birds within Columbia. There are over 50 fruit dove species scattered across the Australasia region. All of them are in the genus telanopus. That's with a silent pea, like pterodactyl or tarmigan. Fruit doves tend to be bright green with patches of yellow, white, and magenta. Outstanding examples include the many-colored fruit dove, the superb fruit dove, and the golden dove. But arguably, the brightest of all is the orange dove, Tilinopus Victor, which lives on only a few islands in Fiji. The male of this species is a glowing orange color all over, but with a yellowish green head. It's a stunning bird.

And I have a personal connection with this species. Or at least I really want to have a personal connection with it. Are you familiar with the term nemesis bird? This is birder slang for a species you've tried to see more than once, but it keeps eluding you. Maybe other birders have seen this species no problem, and they like to tell you about how easily they found it. Well, the orange dove is the closest thing I have.

have to a nemesis bird. This species is on the cover of the old field guide I have for Fiji. I've been to the country on three occasions now, two of which were to lead birding tours there. Have I seen an orange dove? Nope. No orange dove. Now to be fair, we didn't try super hard to find the species, and it's not that common in any case. So hopefully there will be a next time in Fiji, and if so, you better believe I'm going to work extra hard to find that little orange bugger. Back to the plumages of pigeons and doves. I want to add that a few species have elaborate ornamentations on their plumage or bills. The Nicobar pigeon, for example, wears some long, shaggy neck feathers.

Even without these ornaments, the Nicobar pigeon is incredibly handsome, with its overall dark plumage and iridescent upper parts that are deep green, blue, and copper. Also, the name Nicobar sounds like a product for people who are trying to quit smoking. Next time you're itching for a cigarette, reach for a Nickabar instead. It's a candy bar, but with a flavor chain smokers will love. It's like the scrapings from a beer-soaked ashtray rolled in chocolate. Nickabar! Some pigeons and doves have crests of feathers on their heads, such as the aptly named

crested pigeon, Osofap's Lofodes, a common species across Australia. The four species in the genus Goura take this whole crest thing to an extreme. These are the crowned pigeons, among which are the world's largest members of the family Columbidy, as we just discussed. crowned pigeons wear elaborate, lacy mohawks of feathers on their heads. This crown looks to me like a miniature version of the iconic train of a peacock. It's pretty wild and pretty awesome. Behaviorally, pigeons and doves are not super aggressive birds.

A 2017 study published in the journal Behavioral Ecology backs this up with data. I mentioned this research in episode two of the podcast. which was about competition between bird species. The researchers in that study gathered lots of data about the dominance hierarchies among species at bird feeders in the U.S. and Canada. 136 species were analyzed overall. It turned out that the handful of doves and pigeons included in this study were less dominant than expected based on the patterns in the data.

Most birds of their size, their body mass, tended to be more dominant against smaller birds. But, as we already discussed, doves and pigeons are tender creatures. They let themselves get bullied by other birds far too often. I mean, geez, if they only had gallbladders, then maybe they would stick up for themselves. A behavior you may have noticed in doves and pigeons is the exaggerated head bobbing they do when walking. And these birds walk.

They put one foot in front of another rather than hopping as many small birds do. So what's up with all this head bobbing? There's actually a very good reason for it. What's happening is that a pigeon is keeping its head still for a moment while its body is moving forward. While the head is stationary, the bird can more easily detect any movement in its surroundings, like a predator or other danger. After that brief moment of cranial stasis, the bird's head shoots forward, sort of catching up to the body, and then the whole motion repeats.

Interestingly, scientists figured out that a dove or pigeon won't bob its head this way when it's walking on a treadmill. This makes sense, doesn't it? Because a bird probably doesn't have to worry so much about predators when it's busting out some cardio at the gym. It can just let its guard down, walk on the treadmill, and listen to a podcast, or maybe rock out to some songs by Nickelback. I'm told birds love Nickelback.

Actually, pigeons don't bob their heads on the treadmill because the static view offers no visual stimulus for the bobbing instinct to kick in. They don't bob their heads when they're blindfolded either. Like when a dove is blindfolded in a game of pin the tail on the donkey, or when it's trying to hit a pinata. A pinata shaped like a house cat and filled not with candy but sunflower seeds and delicious cracked corn. Birds in the family, Columbidy, also have a special ability when it comes to drinking. Most other birds, dip their bills to scoop up a small amount of water, then lift and tilt their heads back to toss the water down their gullets. But doves and pigeons can actually suck water up, sort of how

you and I do, sort of. They stick their faces into the water, completely submerging their bills, then they gulp. This avian superpower may be an adaptation for drinking water quickly, to minimize the time spent in a vulnerable position. If that's true, However, I wonder why more birds don't do this. In any case, pigeons and doves tend to drink a lot of water. Some species drink up to 10 or 15% of their body weight a day. Humans typically drink 5% or less. Now, before moving on, we should talk about the sounds that pigeons and doves make.

These are definitely not songbirds. They belong to a more ancient bird lineage, and they can't do all that fancy virtuoso-style singing. Birds in this family produce relatively low-frequency songs. Think of the cooing sounds you've heard city pigeons make. You know, this sort of thing. And now here's the morning dove, Zenaida Macroura. And that's morning, M-O-U-R-N-I-N-G. Like mourning for a deceased loved one.

That does sound rather melancholy, doesn't it? This next one is the Eurasian collared dove, Streptopelia deca-octo. This species was introduced to North America in the 1970s and has since spread to just about every corner of the continent. It's sort of an invasive species. Here's the Eurasian collared dove. You'll hear the cooing sounds it makes as well as the so-called excitement cry. Unlike the morning dove, which sounds, well, sad, the Eurasian collared dove has a more upbeat tone, at least to my ear. Like the collared dove knows it doesn't belong in North America, but it doesn't care what you think and it's feeling pretty smug about the whole thing. Here's a song that's a little higher pitched.

This is the ruddy pigeon, Patagioenus subvenacii in Colombia. Some members of the Columbidee family also make non-vocal sounds. The morning dove, for example, makes a whistling sound with its wings while in flight. Ornithologists don't know exactly what the function of this sound is, but it seems to work as a sort of alarm. If one dove bursts into flight and makes this whistling sound, other doves and even birds of other species will freak out and take off as well. Here's what the non-vocal whistling flight of a morning dove sounds like.

Okay, let's switch gears now to talk about the diversity, distribution, and habitats of doves and pigeons. The family Columbidee is the only family in the order Columbiformis. That means that pigeons and doves don't really have any other birds you could call their close relatives. But their closest relatives seem to be the sand grouses of the family Teroclite and the Messites of the family Mesotis. Tornithy. Sand grouse are found in Africa and Asia. Many of them live in incredibly arid places like the Sahara Desert. Messites include several bird species found only in Madagascar. Columbia is a diverse bird family that includes 332 species. Those species are divided into about 45 genera. The genera that contain the greatest numbers of species are Tilinopus with 55 species.

Those are the fruit doves, remember? Then we have the 39 imperial pigeon species in the genus Decula. Colomba, the genus of your common city pigeon, has 36 species. And Treyron has 29 species. Those are the green pigeons. You know, I've just been throwing around the words dove and pigeon, haven't I? Maybe you're wondering, well, what exactly is the difference between a dove and a pigeon? The answer is

Not a whole heck of a lot It's pretty arbitrary actually It seems the smaller species are more often called doves But that's not entirely consistent But as far as I know There are no biological differences That divide birds in this family Into doves on one side and pigeons on the other

Languages other than English don't usually even bother to make this distinction I used to study frogs back in the day when I was working as a biologist, people would sometimes ask me what the difference is between a frog and a toad. It's the same sort of situation. There's no real difference. It's just a byproduct of people naming things haphazardly without fully understanding the underlying genetic evolutionary relationships among animals. Frogs and toads are all species in the order anura. I can't point to any one thing that divides them. Likewise,

Pigeons and doves are all just birds in the family, Columbidae. Case in point, the bird species Columba Livia is sometimes called a rock dove and sometimes it's called a rock pigeon. So which is it, people? The only solid thing we can hold on to in a confusing, disorienting situation like this is the good old scientific name. Columba Livia is the scientific name of your humble city pigeon, regardless of whatever you call it in your language. Okay, so we've got 332 species in the family Columbity. What is their geographic distribution across the globe? Well, I can tell you right now where you won't find any of them.

If you've been listening to the Science of Birds podcast for a while, you should know by my tone of voice alone what I'm about to say. You won't find any doves or pigeons on the continent of Say it with me Antarctica You'll find them just about everywhere else, however. This is a cosmopolitan family. Across all the other continents,

these birds are cooing at each other and bobbing their little heads all over the place. But interestingly, pigeons and doves are absent from the higher latitudes of the northern hemisphere. There aren't any in northern Canada, Alaska, or Siberia. But party central for Columbid birds happens to be on the vast island of New Guinea and the surrounding islands of the Indonesian archipelago. This is where the highest species diversity is concentrated. Birds in this family occupy a wide range of habitat types across the planet. You'll find them

in deserts, grasslands, woodlands, and rainforests. And one species seems to be doing rather well in concrete jungles, from Singapore to Rome to Buenos Aires to Honolulu. The rock pigeon, of which I am speaking, will, at some point, be the focus of an entire podcast episode. So I'm not going to say much more about that species today. If we ignore the rock pigeon and its non-native buddy, the Eurasian collared dove, what columbid bird species are most frequently reported in North America? These would be the morning dove, the white-winged dove, and the Inca dove. All of these species do pretty well in agricultural areas and suburban environments.

So it's not surprising that they often run afoul of humans. In South America, the most common species are the eared dove and the ready ground dove. Both are widespread on the continent and do pretty well in rural or suburban areas. People in Europe most frequently encounter these native species, common wood pigeon, European turtle dove, and stock dove. Europe is also crawling with Eurasian collared doves. It's a non-native species there, too, just like it is in North America. In Asia, the most commonly observed species are spotted dove, oriental turtle dove, and zebra dove. The zebra dove is found mostly in Southeast Asia, but humans have introduced it all over the place. It's hard to say where exactly

its native too. If you're in Australia, the native species you're most likely to encounter are the crested pigeon, common bronze wing, and peaceful dove. Isn't that a nice name, peaceful dove? It makes me wonder, though, is this species even more timid and non-confrontational than other doves? Is it the most passionate follower of meekness? Or is peaceful dove kind of a redundant name? Like if we had other animal species called the annoying mosquito, the swimming fish, or the trash-eating raccoon? Where and when did the family Columbidy originate?

The fossil record is pretty weak for this group of birds, so fossils aren't much help in answering this question. Biologists interested in the evolution of doves and pigeons have had more success using genetic data to reconstruct the evolutionary relationships among birds in this family. There are still many uncertainties, but some evidence suggests that the ancestors of our modern columbids split off from the ancestors of the sand grouse way back in the Cretaceous period when the non-avian dinosaurs were still cruising around. That was maybe 70 million years ago.

Geographically, it seems this happened in the New World, in the Western Hemisphere. Possibly. More recent evolutionary events in the family are a little less fuzzy. For example, the evolutionary lineage of Columbadi really started to diversify big time between 45 and 25 million years ago. That's when the evolutionary tree for this family sprouted a bunch of new branches, new lineages. Today, a lot of the species diversity we see in doves and pigeons is spread across islands in Indonesia and Oceania in the Pacific. This is a major pattern in the evolution of the

family Columbidy, a tendency for endemic species to form on remote islands. As I mentioned earlier, these birds are strong flyers. It seems they're able to reach islands fairly easily, compared to some other types of birds. In particular, the two groups that have colonized a bunch of islands are the fruit doves of the genus Tilinopus and the imperial pigeons of the genus Decula. Starting maybe around 30 million years ago, the ancestral fruit doves began to spread to islands in the Pacific Ocean.

Later, multiple waves of colonization by imperial pigeons started about 20 million years ago. islands tend to be places where new species form because of their geographic isolation and small size compared to the mainland. I'm still planning on doing an entire episode on the subject of the island biogeography of birds. It's fascinating stuff.

So now we have all this diversity of doves and pigeons on islands. We have, for example, the velvet dove, Tilinopis Layerdai, also known as the whistling fruit dove. It's another endemic species in Fiji, where it lives on only two tiny islands. This species is a vibrant green color, and the male has a yellow head. Here's what the velvet dove sounds like. You can see, or rather hear, why one of this species,

common names is whistling fruit dove. The tendency for doves and pigeons to fly long distances and end up on far-flung islands has resulted in the evolution of some other weird and wonderful species. The most famous pigeon of all is, of course, the dodo. The scientific name of this bird is Raphis Cuculatus. It was a giant, flightless pigeon, larger by far than any living species. It lived on the island of Mauritius, which is in the Indian Ocean east of Madagascar. As we all learned, by the time we were five years old, the Dodo is extinct. It disappeared from the world in the late 1600s. Humans were the cause, of course. The Dodo's closest relative was also a big flightless species that lived on only one island. The Rodriguez

Solitaire, Pisa Phap's Solitaria, lived on Rodriguez's Grieges Island until the late 1700s. The evolution of flightlessness on islands seems to be related to a general lack of predators and an abundance of food. This happens in other bird groups as well. There's yet another example from Fiji. Recent fossil evidence led to the discovery of an extinct pigeon from Fiji that was bigger than any living species and was also flightless.

Its closest relatives appear to be the modern-day crowned pigeons. It died out long before humans reached Fiji, so for once we can't blame ourselves for this one. At the beginning of the episode, I was telling you about how my supporters on Patreon helped me choose the subject of this episode. And of course, the support of my patrons helps me make this show possible. So I want to take a moment to give a shout out to the newest patrons of the Science of Birds podcast. Hello and thank you to Susan, Donna, Emily, Vero, Teal, Christine, Pamela, Jesse, Diana, Henry Claude, Jennifer, David, Annette, Justin, and his son Sebastian, Michael, Phyllis, Anand, and Audra. Now, if you are interested in becoming a patron, you'll find a link to my Patreon page in the show notes.

And you can also just go to patreon.com forward slash science of birds. We were just talking about extinctions, of the dodo and whatnot. I wish those were the only stories of human-caused extinction I had to tell you for this group of birds. But, of course, there are more. The extinction of the dodo is so well known that this species is a symbol of anthropogenic extinction. I mean, if something goes extinct, becomes obsolete, or disappears from the earth, we say it went the way of the dodo. Sadly, there's another well-known cautionary tale about extinction

that centers on a member of the Columbidy family. The passenger pigeon, ecto-pistis migratorious. Flocks of this North American species were numbered in the hundreds of millions of birds, maybe even billions. They darkened the sky when they passed over. Aldo Leopold wrote this about the species. Quote, The passenger pigeon was no mere bird. He was a biological storm. He was the lightning that played between two biotic poles of intolerable intensity, the fat of the land and his own

zest for living. Yearly, the feathered tempest roared up, down, and across the continent, sucking up the laden fruits of forest and prairie, burning them in a traveling blast of life. end quote. The last passenger pigeon, Martha, died at the Cincinnati Zoo in 1914. In the previous decades, people had relentlessly hunted her kind for food and sport, and they cut down the forests that these birds depended on. The passenger pigeon went from being the most numerous bird in North America to being the first species to go extinct at the hand of Euro-Americans. Kind of hard to believe, isn't it? I'll leave the full story of this species for another episode.

Another 16 species were driven to extinction in the last few hundred years. Birds like the spotted green pigeon, red mustached fruit dove, and the Tana ground dove. Most of these species lived on islands. One species is extinct in the wild, but still lives on in captivity. This is the Socorro dove, Zenaida Graysonai. Until the 1950s, it lived on the tiny Socorro Island off the west coast of Mexico. Between 100 and 200 Socorro doves are in captive breeding programs in the U.S., Europe, and Mexico. The hope among conservationists is that this species will be reintroduced to its home island someday.

Feral cats were likely the main factor in this dove's decline. There's now a program to eradicate all feral cats on Socorro Island. Until those cats are gone, reintroduction of the dove might not be successful. A bunch of other doves and pigeons are threatened to some degree. The IUCN Red List has 45 species in the near-threatened category. 36 are vulnerable, 18 are endangered, and 11 are critically endangered. Most of these are, surprise, surprise, species that live on islands. The Negros Bleeding Heart, Gala Columba Kiai, is a critically endangered species in the Philippines.

This gorgeous bird has a hood and mantle of metallic green, a white throat and belly, chestnut colored wings, and a little patch of blood-red feathers on its chest. Thus the name Negros Bleeding Heart. Here's the song of this endangered species. The biggest threats to columbid birds in general are, one, habitat loss and habitat fragmentation due to human deforestation and agriculture, two, hunting for food, and three, introduced predators like cats and mongooses. Doves and pigeons these days may not have to worry about being menaced by dragons,

like they apparently did in the Dark Ages, but now they face an even more powerful force, humanity. And as far as I know, there are no paradoxion trees to which these birds can fly to escape us. What do birds in this family eat? And how do they forage? Well, there are two main categories here. You got your granivores and your frugivores. Granivores eat grains. In other words, seeds. These birds include the rock pigeon, morning dove, and most of those more common species I listed out earlier. We see more granivores in agricultural, suburban, and urban areas because, humans leave lots of seeds laying around for these birds to scarf.

Frugivores like to chow down on fruit. So they don't call them fruit doves for nothing. The 55 species of fruit doves in the genus telanopus do indeed eat fruit. And with their colorful plumages, they sort of look like plump little fruits themselves. They look positively adorable and delicious, and I just want to eat them up. A whole bunch of other species are similarly frugivorous. including the diverse imperial pigeons and green pigeons. There are some key anatomical differences between the seed eaters and the fruit eaters.

The gizzard is an enlarged portion of the digestive tract in birds. Food from the stomach is passed down to the gizzard, which has thick muscular walls that help grind up the food. Granivorous doves and pigeons have a thick walled gizzard, esophagus, and intestine. This makes sense because they eat. eat tough, hard seeds. Frugivores, on the other hand, have relatively thin walls in their gizzards and the rest of their digestive tract.

Fruits are soft and squishy and don't need as much mechanical grinding like seeds. Many fruit-eating doves and pigeons forage in the branches of fruit-bearing trees or bushes. These birds tend to have grasping feet that allow them to hang upside down in their efforts to pluck hanging fruit. Seed eaters usually forage on the ground. Some pigeons and dove species will also eat insects or other small animals on occasion. Weirdo alert. Weirdo alert. In the forests of Samoa, on a couple islands way out in the middle of the Pacific Ocean,

lives the tooth-billed pigeon, didunculus strigorostris. This large, chunky pigeon is about a foot long or 31 centimeters. Its head and underside are a gray blue, and the rest of its plumage is a dark rufous color. But that bill! The bill is what sets this species apart and makes it worthy of today's weirdo alert. The bill is way thicker than that of your average pigeon or dove. It's almost vulture-like. The upper bill curves sharply at the tip. The lower bill has three-pointy projections that do indeed look like teeth.

But of course they aren't like the teeth of mammals. They're just extensions of the bird's bill. The tooth-billed pigeon uses that special strong bill to eat the tough seeds of wild mahogany in Samoa. The tooth-billed pigeon is the only species in the genus Dydunculus, so it doesn't have any close relatives. One of its closest relatives may have been the dodo. One name suggested for the tooth-billed pigeon back in the day

was actually doodlet, as in small dodo. The genus name, Dydunculus, translates to Little Dodo. There's also some evidence that this bird represents one of the most ancient lineages within the family Columbity. This weird and wonderful pigeon is actually the national bird of Samoa. Its local name is Manumea. The tooth-billed pigeon has been featured on the bills and coins of Samoa's currency, the Tala.

Unfortunately, the Manumea is one of the critically endangered species in the family Columbidi. There are probably less than 200 left in the wild, and there are none in captivity. The species is threatened by habitat loss, hunting, and introduced species like pigs and rats. So without some major conservation efforts, the tooth-billed pigeon, the doodlet, may also go the way of its cousin, the dodo. Pigeons and doves are monogamous breeders. Pairs stick together for a season, a few seasons, and maybe for life in some cases. Males of some species show courtship behaviors involving vocal sounds, postures, and displays, including flight displays.

Rock pigeons are colonial nesters, as was the passenger pigeon. Nest construction in this family is pretty shoddy. Columbid nests are typically flimsy and loose. They're made of a little pile of sticks, twigs, and scraps of vegetation. The nest is often constructed by the female, but in some species the male does this work. Both sexes take care of the young, and this includes egg incubation. Mom and dad take turns sitting on the eggs. When the eggs hatch, the parents also share in feeding duties.

Now here's where this gets really interesting. Doves and pigeons have another superpower. besides being able to drink face down in the water. Breeding birds in this family produce something called crop milk, or pigeon milk. This is a nutritious, semi-solid secretion made in the bird's crop. The crop is an expanded part of the esophagus, where birds temporarily store food before digesting it. So when a hatchling pigeon or dove begs for food,

mom or dad obliges by letting the youngster stick its head straight into their gullet. The baby bird eats the crop milk, which is more like cottage cheese than cow's milk or human milk. Crop milk is rich in protein, fat, and antioxidants. I'm sure it's quite delicious, too. I mean, who knows? Maybe someday we'll have another option at Starbucks, besides soy milk and almond milk. Yeah, hi, I'll have a grande, half caramel, half vanilla, decaf latte with crop milk. crop milk like you know pigeon milk you don't have that crop milk you can you can google it but seriously

where am i the soviet union no but yeah but yeah i need to speak to your manager because pigeons and doves make crop milk for their young they don't need to find insects to provide them with a necessary protein this is probably one key to the success of birds in the family columbidi Many have extra long breeding seasons because they aren't reliant on the seasonal availability of insect prey for their chicks. The absence of a gallbladder doesn't seem to have been a liability for pigeons and doves. This is a widespread, diverse group that has been around for many millions of years. These birds occupy numerous habitats across the planet and they've managed to colonize. countless remote islands. Many of them are as richly colored as parrots or songbirds. I hope you agree with me

that we should appreciate and protect these little marvels of nature. Not so we can harvest their crop milk for our lattes, but because we don't want to lose any more of them. The dodo, the passenger pigeon, the Rodriguez Solitaire, and all the others have taught us more than enough already about the consequences of our greed and carelessness. If you were at all skeptical about the awesomeness of pigeons and doves, I hope I helped sway you a little towards loving these birds. My own appreciation for them is even deeper now after doing the research for this episode. Thanks so much for being here and for listening today, seriously.

And if you haven't already signed up for the Science of Birds email newsletter, you should hop over to scienceofbirds.com and enter your email address. You'll have another way to stay connected to me and to the show. If you have something you'd like to share with me about the podcast or about how easy it was for you to find the orange dove in Fiji, please shoot me an email. The address is Ivan at scienceofbirds.com. The show notes for this episode, which is number 32,

are on the science of birds website, scienceofbirds.com. This is Ivan Philipson. I hope you can get out to see some birds soon, and I wish you a happy day. Peace.