The Science of Birds - Grebes

Episode Date: August 30, 2026

👕 Bird Merch —  Get yourself some bird shirts!~~~Enter the murky aquatic realm of the family Podicipedidae in Episode 137 of the The Science of Birds podcast. Often mistaken for ducks, loons, or coots, grebes are unique, fascinating waterbirds with some bizarre physical traits and behaviors.The episode covers everything from the specialized lobed toes of grebes and rear-positioned legs to their spectacular, highly synchronized courtship dances. Discover the unexpected identity of grebe's closest evolutionary cousins, learn why these diving birds swallow their own feathers, and explore the precarious mechanics of raising chicks on soggy, floating nests.By the end, you'll know why these fluffy-butted water gremlins are truly great!Links of InterestWestern Grebe walking on the beach [VIDEO]Clark's Grebes Rushing Ceremony in Oregon [VIDEO]Hooded Grebes courtship [VIDEO]Great Crested Grebes courtship [VIDEO]Support the show

I was once in Peru, looking for birds on the largest lake in South America, Lake Tidikaka. I was staying at a lodge on a tiny island in the lake, and I was able to borrow a kayak from the lodge. So I went out and paddled around along the shore of the island. There were soft, reed-like plants emerging from the water. The kayak slipped quietly through the vegetation as I made my way along. The whole scene was peaceful and beautiful, sunny and. and warm. Oh, and I should mention that the surface of Lake Tidikaka is at an elevation of 12,507 feet, which is 3,812 meters. So, yeah, way up there. Before long, I realized that I was not alone in the water.

Here and there, all around me, I saw out of the corner of my eye these little water gremlins popping up and then disappearing with a soft splash. Some kind of mischievous water nymphs closing in around my boat. But you know the topic of today's podcast episode, so you've already deduced that these creatures were not magical spirits of the aquatic realm, but were in fact grebes. Tidicaca grebes, to be precise, Rolandia microptera. This is a medium-sized grebe species with a pointy yellow bill,

a yellow eye ring, a crisp white throat, dark brown and gray upper parts, and rich reddish-brown feathers running along the sides of its neck and flanks. The grebes near my boat were pretty chill and didn't seem all that afraid of me. They just carried on with their foraging, diving and surfacing over and over, sometimes coming up with a little fish. I ended up getting great looks at them up close and a couple nice photos. I'll put one of them in the show notes for this on the Science of Birds website. Anyway, like I always say, grebes are great.

And I really enjoyed seeing those birds on Lake Tidicaca. They were cute and interesting to watch. I knew the Tidicaca grebe was found in only a few high elevation lakes in that part of South America. And so it was an exciting new species for me to see. But only later, when I was back home and looked up more information on this species,

only then did I really really. just how special these grebes are. 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 137. It's all about birds in the family podisipedity.

These are, of course, the grebes. Grebes are familiar water birds in many parts of the world. Because of their habitat and general body shape, some people might confuse them for being ducks or coots, cormorants, or bloons. But as we'll see, grebes are very much their own thing. They have many traits that set them apart. So if you've been stressed out and struggling, wringing your hands in helpless confusion about what exactly makes a grebe a grieve,

Grieb? Well, my friend, today is the day. It's time for us to sort out the family Podis Apedity once and for all. Let's start by looking at the shapes, sizes, and coloration of grebes. They do indeed have a vaguely duck-shaped body, a long neck and a streamlined sort of teardrop-shaped body with the thicker end in the front. Ducks typically have their feet positioned underneath their body in the middle. Grebes, however, have legs that stick out the back, like way at the back, as far as you can go. Loons too have legs positioned at the posterior end of the body,

but the situation in Grebes is even more extreme. Grebes and loons are specialized diving birds, and they propel themselves underwater by paddling with their feet. But just to be clear, grebes are not closely related to ducks or loons. I'm just using those other birds for comparison. One very important distinction is that the feet of grebes are not webbed. Their feet don't have webbing between the toes the way ducks do. Instead, grebes have lobes on their toes. Each toe has a round-edged flap of skin on each side. When a grebe kicks backward, pushing against the water, those flaps, the lobes, spread out,

and generate the force that moves the bird forward. Then when the grebe draws its foot forward in the water, the lobes fold together so that the toes slice through the water hydrodynamically with minimal resistance, minimal drag. Loebate feet, those with lobes on the toes, evolved independently in several bird lineages as an adaptation to a swimming lifestyle. These lineages include the grebes, coots, fallaropes,

and fin feet, or fin foots. Other birds like ducks evolved webbed feet for the same purpose. I'll put a photo of a grebe's foot in the show notes on the website. How about the wings? Well, the wings of grebes tend to be relatively short and broad. Remember the scientific name of the Tidicaca grebe? Sure you do. It's Rolandia microptera. Microptera, microtera, micro-es.

means small wing or tiny wing. Combine having small wings with the fact that grebes have dense and therefore heavy bones, and you'll understand why these birds don't fly so good. Sure, most grebe species can fly, but their flight is not very efficient. They burn a lot of energy trying to stay in the sky with those little wings. So understandably, these birds are often reluctant to take to the sky. They'd rather stay in the water, splishy-splashing around with their low-bait feet. On those occasions, when a grebe does take off from the water, it often has to get a running start.

We see that same thing with loons, too, right? Because loons are also pretty heavy-bodied. Now, the tail of a grebe is, is, well, it isn't, really. There isn't much of a tail. The tail feathers, or rectrices, are essentially vestigial in grebes. When these feathers are even visible, you'll see that they're pointy, short, and wispy. So instead of having a recognizable tail, grebes just have a fluffy little powder puff butt. The fluff feathers are mostly the undertale coverts. So grebes have a vestigial tail. Then you know who else has a vestigial tail?

I do. And so do you. Our primate ancestors had long tails, right? Up to maybe 25 million years ago, but the tail was subsequently lost during our long evolutionary history. But human embryos today still have a temporary tail during weeks four through eight of gestation. And then the tail shrinks leaving behind only the tailbone, or what's known as the Coxix, C-O-C-C-Y-X.

So you and I had a tail for a little while, when we were in our mother's wombs. Okay, so so far we've talked about body-shape in grebes, their feet, wings, and that non-existent tail. Next up is the bill. Bill shapes in grebes vary among species, from short and thick to long, pointed, and dagger-like. This variation is linked with diet.

Grebes with stubbier bills, or small dainty bills, eat a lot of crustaceans and or aquatic insects. Those with the long, stabby-stabby-bills focus their efforts on fish. There's also variation in bill color among species. Some have orange or yellow bills, while most others have black or gray bills. The Australasian and little grebes both have a patch of yellow color at the base of the bill, or it can be a bit greenish in the Australasian grebe or pale blue in the little grebe. Otherwise, the bills of those two species are dark all over. True to its name, the pied-billed grebe has a beak with contrasting patches of black and white. Well, not really white. The overall base color is more of a pale blue,

and then there's a thick black vertical bar running through the middle of the bill. The smallest species in the family Podisipedity is the least greased. grebe, Tachybaptus Dominicus, measuring about nine inches long, which is about 23 centimeters. The least grebe is a neotropical species, found from southern Texas down to Argentina. The largest species in the family should be named, for the sake of grammatical symmetry, the most grebe. But no, instead, the largest podisipedid is named the great grebe, podiceps major. It's up to 30 inches or 77 centimeters long. The Great Griebe is also found in South America.

Now let's look at the feathers, the plumage. Grebes generally have black or gray upper parts. Many species have rust or brown accents, and a few have patches of golden or pale buff feathers. And patches of white are present on the heads and necks of some species. Most species have white or pale gray bellies, their undersides. Breeding adults in a number of species have flashy crests, tippets, or horns. Now, the horns are not true horns, of course, but simply a pair of feather tufts on the sides of the head.

And a tippet, T-I-P-P-E-T, in case you're wondering, is a prominent patch of long or hanging feathers that adorn a bird's neck or the sides of its head. And full disclosure, prior to working on this episode, I did not know what a tippet was, so I had to look it up. And the original historical meaning of this word is a long, narrow strip of fabric attached to a sleeve, hood, or hat. The great crested grebe gives us a great example of tippets. This species grows these shaggy, rufous and black feathers

on the sides of its head during the breeding season, and those are called tippets. In fact, one historical common name for the great crested grebe was tippet grebe. A key feature of birds in the family potis appetidae is that their plumage is super dense. An individual grebe has about 20,000 feathers in total. Now, that number might not mean anything to you at first,

but realize that a swan, which is a way bigger bird might have that same number of feathers. And a sort of grebe-sized duck, like a mallard, has only about 12,000 feathers. You can imagine why such dense plumage is a useful adaptation for grebes who spend most of their time diving around in pretty cold water. Dense feathers help grebees stay warm and dry. Remember from the podcast episode I did on penguins that those birds have the densest plumage of all. for the same reasons.

Another distinguishing feature in grebes is their eyes. Their intense, staring, spooky eyes. Depending on the species, the irises can be bright yellow, orange, or scarlet red. Their eyes can even have two or more colors in concentric rings. So when a grebe stares at you with its red circles within circle's eyes, you might feel like it's trying to read your thoughts or hypnotize you. You know, like Ka the Snake in the Jungle Book, or like some kind of hypnogreeb.

And if you don't recognize that sound, please go watch every episode of the show Futurama, and you'll thank me later. Now the Piedbilled Grieb is an exception when it comes to eye color. That species has very dark brown eyes. So it looks to us probably like it's friendlier, warmer, less intense. As a last note about coloration and plumage in grebes, I should tell you that there aren't really noticeable differences in the plumages of males versus females, so grebes tend to

lack sexual dichromatism. Okay, let's talk about a few key behavioral traits in grebes. They're expert divers, and one reason for that is, as we discussed, their legs are attached way at the back end of their bodies just below that floofy little butt. And grebes have those low bait feet for paddling. Most species can fly, but they're not all that great at it. Walking on land is another option for locomotion. But because of how their legs are positioned and because of their lobed toes, grebes basically suck at walking. They can walk, yes, for short distances, if they have to, but I have to say it's kind of cringe. A walking grebe has an awkward, hunched, partially upright posture. It lurches or skips along until it can get back into its comfort zone, some nice water to splash into.

I'll put a link in the show notes to a video of a western grebe walking on a beach. It's good stuff. Now, I don't know about you, but I usually resist the urge to eat large wads of my own hair. because, like most humans, I'm disgusted by the idea of eating hair, disgusted at a deep, primal level. That's not surprising because keratin, the protein that hair is made of, is completely indigestible to human stomach acids. Well, feathers are also made of keratin. I also avoid eating feathers, as do most birds. But not grebes. Yet another distinguishing behavior of grebes is that they do, in their own feathers. And for hundreds of years, this odd behavior baffled naturalists and ornithologists. But now it seems we've pretty much got it figured out. Griebs eat feathers,

not because they can digest the feathers for any nutritional value, no, but because it's a nifty adaptation for dealing with the spiky, crunchy things they eat. It works like this. A grebe will pluck some feathers from its flanks during preening. And then it swallows those. And once swallowed, the feathers end up in two distinct places in the stomach. One, there's a large wad of feathers, a bolus, if you will, that ends up in the gizzard. And two, there's a highly compact ball of feathers that sits in the pyloric pouch. And this little ball of feathers is called the pyloric plug, P-Y-L-L-R-I-C-Pyloric. That large feather bolus in the gizzard has a couple of functions.

First, it keeps food around long enough to be digested with chemicals. Unlike many birds, grebes don't swallow grit or rocks to help break down the food they swallow. They depend entirely on chemical digestion. The feather bolus holds the food within the stomach, keeping it exposed to highly acidic gastric juices until it is fully digested and liquefied. And the second function is that the dense, fibrous mass of the feather bolus wraps around any sharp hazardous bits and pieces of prey, things like bones or the exoskeletons of crustaceans or insects.

The mass of feathers keeps these things from damaging the bird's internal tissues. Okay, so that's the bolus and the gizzard, and then we have the pyloric plug. That's the dense ball of feathers in the pyloric pouch. That works primarily as a filter. It sits at the narrow passageway between the stomach and the intestines. The pyloric plug strains and filters stuff that's moving through this part of the digestive system. It's dense enough to block almost all solid, undigested, or indigestible matter from getting into the intestines, allowing only liquids to pass through.

Because the pyloric plug blocks solid debris from moving forward, indigestible items inevitably accumulate in the stomach. To clear this build up and prevent injury or obstruction, Grebes need to regularly hack all that stuff up in the form of a pellet. And during this hacking up process, grebes regurgitate a pellet formed from mucus-covered feathers mixed with undigested bone and bug fragments. The pyloric plug itself is sometimes expelled during these hacking episodes. This system, with the feather swallowing, the bolus, the pyloric plug, and all that,

is so important in grebes that feathers are often the very first thing parents feed to their newly hatched chicks, because a baby grebe needs a pyloric plug to protect its tiny digestive tract. Let's move on to the vocal sounds made by grebes. These birds make a diverse range of loud, often harsh, sounds, including metallic trills, purring, nasal advertising calls, and what some have described as donkey-like braying. So see what you think of this song. This is a pair of rednecked grebes in Sweden. They're the ones making the harsh sounds that you hear. But you'll also hear a whooper swan making a single honking note. So again, those were rednecked grebes, and yeah, I would say pretty donkey-like

indeed. Next, let's listen to some Western grebes making their strident noises in their breeding colony. This was recorded in California. Our next recording was made in Finland, and it's of an eard grebe. But in Europe and Asia, they tend to use the common name black-necked grebe for this species. A familiar sound heard in wetlands across North and South America is the song of the Pied Build Grebe. It's impressively loud and dramatic, given how small and compact this bird is. Next up is the wild-sounding trill that is the call of the Madagascar grebe. The Hunan grebes in this recording, which was made in Peru, are giving relative soft, unobtrusive calls. Again, these are the Hunine Grebe, J-U-N-I-N. Where do the word

grebe come from? Well, it seems to have been used in English starting back in the 1700s, but its origin is unknown. It might have come from a Celtic word meaning comb, which would perhaps refer to a grebe's crest feathers. Griebs have had other common names in English over the centuries, names like dab chick, ducker, dipper, diver, and the best of all, arsefoot. No, I'm not joking, arsfoot. I mean, it's pretty spot on, right? Because the legs are positioned so far back on the body, near the, yeah. Now, we might not know the etymological origin of the word grebe,

but the family name Podisipedity is easier to sort out. It's basically arsfoot, but in, fancy Latin. Podicipedity comes from Podex, which means vent or rear in Latin, and PES, P-E-S, which means foot. So, rear foot. As I mentioned, it's easy to imagine that grebes would be related to ducks or coots or cormorants, but the resemblance there is only superficial, as I said. It actually took a long time for ornithologists to figure out where grebes fit on the avian tree of life. In other words, to figure out their phylogenetic position on the tree and to describe them taxonomically. At one time, grebes were thought to be close relatives of loons,

and some ornithologists have also proposed that grebes are closer to coots. But I'm happy to say the mystery has been solved. A bunch of genetic and morphological data from things like skeletal features has revealed that the birds' most. most closely related to grebes are Flamingos. That's right, flamingos. Pretty crazy, right? Because, I don't know about you, but the close relationship between grebes and flamingos that we know is true is definitely not obvious.

Of course, if you already listened to the episode I did on flamingos, you may remember this unexpected connection. Grebes and Flamingos share lots of similarity at the genetic level, as revealed by DNA, but they also share a bunch of anatomical features, morphological features. To give you a simple and easily understandable example of such a shared anatomical feature, consider that in both Grebes and Flamingos, the pars acetabularis of the musculus iliotibialis lateralis is absent. Another feature these birds share is that their eggs are covered with a chalky white layer of calcium phosphate.

These two groups of birds belong to two different families, Podisepedee for the grebes and phenocopterody for the flamingos. And those families are separated into two different taxonomic orders as well. But looking at the evolutionary relationships as shown on the avian tree of life, we see that greaves and flamingos are both on a branch, or we can call it a lineage or a clade, that ornithologists have named Mirandornathies. This isn't a family or an order, but something a bit more inclusive than an order, but it contains only the grebes and flamingos.

The name Mirandornathes brings together Latin and Greek words, and it translates as Wonderful Bird. And that's fantastic. I think we could all agree with that assessment that Grebes and their cousins, the flamingos, are indeed wonderful. I have not yet told you how many species are in the Grebe family.

How many would you guess? 8,911? 4? Negative 62? Wrong, no, and incorrect. I mean, it's definitely not four because I've mentioned at least six species in this episode already. I'm actually surprised by the real number. It's lower than I would have guessed. There are just

19 species of grebes. That's it. 19 species divided into six genera. Podiceps, spelled P-O-D-I-C-E-P-S, is the genus with the most diversity, containing eight species. And the next most diverse genus is Tachyabaptis with four species. Even though there are just 19, species, you'll find at least one of them paddling around in your local waterways just about anywhere on Earth. In other words, the family podisipedity is cosmopolitan. Griebes live on every continent except, of course, Antarctica. That's because grebes are wise. They know what's up. Grebes can see Antarctica for what it is, a cursed continent, entombed in ice, anathema to life itself. A place whose bitter wind and fearsome frigidity extinguish all joy and all hope forever and ever.

Yes, I'm being silly. If you don't understand why I spew so much vitriol at Antarctica, just listen to some more episodes. Anyway, of all the continents, South America is the one that harbors the most species diversity for grebes. About half of the world species can be found there. Some grebe species have very small geographic ranges, while others have massive ranges. In the latter category we have, for example, the eared grebe. And again, that species also goes by the name Black Neckd Grebe. This is the world's most abundant grebe species, with populations in North America, Europe, Africa, and Asia.

Other species with large, multi-continental ranges include the horned grebe, great crestace, Grieb and Rednecked Grieb. Looking at data from the I-Naturalist app, we see that citizen scientists in North America most commonly report seeing the Piedbilled Grieb. And then that's followed by the horned grebe, eared grebe, and Western Grebe. In South America, the species observed most frequently

are the Great Grebe, White Tufted Grieb, and the Piedbill Grieb. In Europe, the most common species is the Great Crested Grieb, In both Africa and Asia, it's the little grebe that appears to be the most common. And then in Australasia, the winner is, fittingly, the Australasian grebe. And finally, the most commonly observed grebe species in Antarctica is... Ah, that's right. Nada. When it comes to migration, we see an assortment of strategies among grebe species.

Grieb populations or species living in the southern latitudes are generally sedentary, so they don't migrate. The species and populations that breed further north, however, are migratory. For example, the rednecked grebe, potuseps grizzagina, is very much a northern bird, in Europe, Asia, and North America. Rednecked grieves breed in inland freshwater bodies like shallow lakes, marshes, and bogs. So these places ring with the beautiful donkey-brewing songs of rednecked grebes in the breeding season. I was recently in Anchorage, Alaska, and I saw a bunch of rednecked grebes sitting on their nests in a shallow lagoon. It was really cool. This species migrates, and it spends the winter in the ocean along the coast. They hang out near shore in bays and inlets. Many northern populations of

Eard Grebe and Great Crested Grebe are also migratory. And it seems most, if not all migratory grebes, make their long journeys at night. Eard grebes are famous for congregating in massive numbers at these hyper-saleen lakes, or salty lakes as they prepare for migration. Mono Lake in California, the Great Salt Lake in Utah, and the southern end of the Caspian Sea are the best examples of these staging areas. Like other grebes and many other water birds, Eard grebes lose all the flight feathers from their wings at once.

They do this every year when they molt. It takes 35 to 40 days for new flight feathers to grow in. So until then, the birds are effectively flightless. During this staging period, Eard grebes fatten up on tiny crustaceans in the salt lakes. The birds actually double or even triple their weight. their physiology changes dramatically. Then just a few weeks later, that process is reversed.

The grebes stop eating, they lose a ton of weight, and their bodies transform into efficient long-distance flying machines. In general terms, the breeding habitats of grebes include shallow freshwater lakes, marshes, and ponds, with lots of emergent vegetation for anchoring their nests. We'll get to talking about nests in a moment. For migratory grebes, the non-breeding habitat is usually some kind of salty lake or a near-shore marine environment. We know that the closest relatives of grebes are flamingos, right? And that is a very cool, fun fact.

But when did those two groups of birds go their separate ways? When was the evolutionary split between the family's podisipedity and phenocopterity? Well, if we look at the fossil record, we see that true grebes appear rather suddenly during the late oligocene or early Miocene, roughly 23 to 25 million years ago. The common ancestor of grebes and flamingos and their split had to have happened well before that time. And indeed, evidence from DNA, using the molecular clock approach, suggests that the split happened about 40. million years ago. So about 15 million years before we find the first legit grebe fossils. In any case, it seems that the Mirandornathies lineage evolved from an ancestor that was a highly aquatic swimming bird. There are some fossils of birds in the extinct genus Juncatarsus. They lived

during the Eocene epic, so between 56 and 33 million years ago. One of these Juncatarsus species might be the closest to the common ancestor of grebes and flamingos. Now, while we're on the topic of evolution, there's another thing we should talk about. As we've been saying, grebes are highly specialized birds, specialized for diving. And as we've seen, that has come with the major trade-off of not being all that great at flying or walking. Because of their physical constraints, grebes are reluctant. fliers, and they rarely take to the sky other than during episodes of nocturnal migration. So just as the default, grebes suck at flying, they know they suck at flying, and they don't like to do it.

And then imagine this scenario. You've got a lake with very stable conditions. It's located in the tropical latitudes, so the weather is pretty similar all year. And food and other resources are pretty much guaranteed year-round. For a grebe, living in a lake like that, the pressure from natural selection to maintain the ability to fly is sort of relaxed. Natural selection just takes a break and chills out. Because in such a stable environment, you don't need to fly. So why spend tons of energy growing and maintaining those big flight muscles? And it turns out that more than one grebe species has ended up in just such a lake, thousands or millions of years ago.

Species from three different genera have ended up colonizing a nice lake, and then those birds each independently lost the ability to fly. There are three flightless grebe species. Well, really only two now since one of them recently went extinct. More on that in a moment. But the point is that flightlessness in the grebe family evolved on at least three separate occasions in three different genera. The three flightless species share some traits. They're larger and heavier than their closest flying relatives. They have shorter wings and they have relatively small breast muscles.

And these species are, one, the Hunin grebe that we heard earlier in which only lives in one lake, Lago Hunin in Peru. Two, the Atitlan grebe, which lived in Lago de Atitlan in Guatemala, but is now sadly extinct. And then three, the third flightless species is none other than my little water-gremlin friend, the Tidicaca grebe. So when I was in my kayak hanging out with those grebes, I did not know that they were flightless. And this whole tendency toward flightlessness in high-elevation tropical lakes is pretty cool, and kind of crazy, because these grebes went from being bad at walking to also being 100% unable to fly. That leaves swimming as the only way of getting around for these birds.

They went all in on staying in their respective lakes forever. That is some pretty extreme and fascinating evolution right there. I just mentioned that the Atitlan grebe is no longer with us. I believe the last this species was seen was in 1989. It was a close relative of the Pied build grebe. There are actually photos of it. The Atitlan grebe basically looked like a pied-billed grebe on steroids, bigger and chunkier. Unfortunately, two other grebe species have also gone extinct in recent times.

The Alaotra grebe used to live in a small part of Madagascar. The last confirmed sighting of that bird was in 1985. And then there was the Colombian grebe, which lived in wetlands in the Andes. It was last seen in 1977. Of the 19 species still with us, the hooded grebe is the most at risk of extinction. It lives in Patagonia, where it breeds in volcanic mountain lakes. The primary threats to this beautiful bird appear to be climate change and introduced non-native predators, the American mink, salmon, and trout.

Birdlife International estimates that there are only about 650 to 800 mature hooded grebes left. This species is ranked in the critically endangered category. And then we have several species ranked as endangered. These are the Madagascar grebe and our two remaining flightless species, the Hunan grebe and the Titicaca grebe. So yeah, I also didn't realize the grebes I was frolicing with in Peru were endangered. As I said, those were very special birds. I knew they were special, but they were even more special than I realized at the time.

The Hunine and Tidikaka grebes are particularly vulnerable because of their limited ranges and their inability to fly away when the going gets rough. The horned grebe, a familiar species in North America, Europe, and Asia, is in the vulnerable category. Populations of this widespread bird are declining throughout much of its range. Grebes face a number of threats. First and foremost is habitat loss, particularly the draining of wetlands. And then there are those introduced non-native predators, introduced fish being the worst offenders,

because the fish can out-compete grebes for small prey, or the fish can even eat grebes, especially the chicks. Bass and rainbow trout are among the kinds of fish that cause lots of trouble for grebes. These birds also suffer from pesticide pollution in their breeding habitats and oil spills in marine waters. Grebes are opportunistic pursuit divers in terms of how they hunt for prey. They chase small animals around underwater, but they also glean prey from the surfaces of aquatic plants or rocks, and they'll pick small invertebrates off the water's surface, and they sometimes snap at flying insects by lunging out of the water. In general, grebes eat fish and aquatic invertebrates, but there are some dietary specializations among the species. As we see in birds of all kinds around the world, the size and shape of the bill in grebes tells us a lot about what they eat.

Now, we talked a little bit about that earlier. Grebes with long, thin, pointy bills are mostly fish eaters. Those with smaller, daintier bills focus more on small aquatic invertebrates like insects. Looking at some examples, Western and Clark's grebes, the two largest species in North America, and the only members of the genus Echmophorus are highly specialized fish eaters. They eat many different fish species. The bills of Western and Clark's grebes are long and dagger-like, or like the tip of a spear. In fact, these grebes do sometimes impale fish with their bills when they're hunting.

And that genus name for the Western and Clark's grebes is Ekemophorus, A-E-C-H-M-O-P-H-H-O-R-U-S, Icumphorus, that comes from Greek and it translates as spear-wielding or spear-carrying. The silvery grebe, Potecepts Oxypitalis, of Southern South America, has a comparatively small short bill. And this species eats small arthropods, including freshwater shrimp and the larvae of insects like cadis flies, midges, and beetles. The flightless, endangered Tidicaca grebe is a fish eater, but a very very large. specialized one. It eats almost exclusively pupfish. These are small fish belonging to the genus Orestius that live in mountain lakes in the Andes. One study of the Titicaca grebe found that over 90% of the prey items in their stomachs were pupfish. The widespread and well-known pied-billed

grebe is a bit more of a generalist. Its bill is relatively short, thick, and blunt. Pied-billed grebes are opportunistic and will eat all sorts of small animals, crustaceans, insects, fish, and amphibians. But they do seem especially fond of crayfish, crabs, and shrimp. A short, stout bill is a good tool for catching and handling larger crustaceans like these. When the hunter becomes the hunted, grebes can become the victims of predators. Adult grebes are targeted by eagles and other raptors, as well as mid-sized predators like mink. Minks? Mink? Plural for mink is what? And sometimes a large fish can gulp down a grebe, or at least try. And there was actually a documented case where a great blue heron ate an eared grebe, which is crazy. The eggs and chicks of grebes are

even more vulnerable. They can get taken out by raccoons, gulls, corvids, fish, and turtles. In terms of breeding, grebes are generally monogamous. They usually pair up in the non-breeding season or while on migration. Grebes are celebrated for having some of the craziest high-energy and highly synchronized courtship behaviors among birds. Because most grebe species have little to know sexual dimorphism or dichromatism, their complex displays are almost entirely mutual. as in both sexes perform pretty much identical displays, in contrast to just the male making all of the fancy moves.

Courtship varies among different grieve species, but it usually involves a series of highly ritualized, mechanical postures, dance moves, and vocalizations. And all of this plays out while swimming in open water. These are the behaviors that establish and maintain paribons. Probably the most famous courtship rituals among North American grebes are those of Western grebes and carx grebes. Both species go through a series of synchronized movements that culminate in the spectacular rushing ceremony. This is where both birds suddenly lunge forward, raising their bodies completely out of the water,

and then they run side by side across the surface for 15 to 65 feet, or 5 to 20 meters. They paddle so furiously with their lobed feet that they're literally running on the water. They're like little speedboats ripping along at full speed, with their hulls rising up out of the water. I'll put a video clip in the show notes of some Clark's grebes doing this rushing ceremony. The clip is from the BBC, narrated by none other than David Attenborough, and it was filmed right here in my home state of Oregon. I'll also put links in the show notes to videos of hooded grebes, and Great Crested Grieves going through their courtship rituals.

You can see the Great Crested Grieves showing off their glamorous tippets. And if nothing else, you've got to watch the video of the hooded grebes in Patagonia. These crazy little birds are hilarious. Their courtship is pretty intense. Now I'm going to outline the general sequence of courtship behaviors in grebes belonging to the genus Potecepts. Remember, there are eight species, including the eared, horned, great-crested, rednecked, and great-crebs. Courtship begins with the discovery ceremony.

This is the introduction and sex recognition ritual between potential mates, consisting of five core steps. And despite what I said earlier, it seems not all of these steps are performed equally by both individuals. Step number one is advertising. An unpaired bird swims with an erect neck and raised crest while giving loud,

species-specific advertising calls to attract partners. Step number two is the cat display. When another bird approaches, the first bird assumes a stationary, crouched cat posture. Or the term, as some ornithologists put it, in which I prefer because it's funnier, cat attitude. In this attitude or posture,

the bird fluffs its body feathers and tilts its bent wings down toward the water to showcase its markings. Often it's the female grieve that adopts the cat attitude. Step number three is called bouncy dives. The approaching bird repeatedly dives toward the stationary partner, swimming with an elevated breast and its head held flat against its back. The cat attitude bird remains floating in place,

but it rotates to face this bouncy diving bird. Step number four is called ghostly penguin posture. The diving bird pops up three to six feet or one to two meters away, and it treads water to stand almost upright. But at first it's actually facing away from its partner, and then it abruptly turns around to face its partner. And I get it that this is called the penguin posture because the grieve is sort of standing straight up like a penguin as it treads water. But why is it called the ghostly penguin posture? I don't know. I mean, ghosts are scary, man. That's all I know.

And I also know that ghostly penguin posture had just been added to my list of possible band names. And step number five is called the penguin dance. Both birds swim close. They come breast to breast, and then they rise out of the water while kicking their little feet rapidly, so that they're both treading water. They go through some synchronized head-shaking movements, and then they slowly sink back into the water and swim off side by side. So, again, that's the sequence that occurs during the discovery ceremony and grebes belonging to the genus Potecepts.

And you thought we were done. But nope, there's more. If the discovery ceremony goes well, the grebes are viving with each other and there seems to be compatibility, then the pair immediately transitions into the next phase. And that phase is called the weed ceremony. And it has a couple of steps. Step number one in the weed ceremony is weed acquisition. Both birds synchronously dive and then come back to the surface with beaks full of aquatic weeds. They're both like, hey, look what I found. Do you like this? I found some weeds. And then step number two is the weed dance and rush. Carrying those weeds, the grebes approach each other, they rise breast to breast, and then quickly turn parallel to perform a weed rush.

running side by side across the water surface for maybe 10 to 15 feet or several meters before they settle back down. So there you go. You got your discovery ceremony, weed ceremony, lots of ceremonies, lots of dances, postures, it's all good stuff. Again, do yourself a treat and watch some of these videos. Now it makes sense that the weed ceremony is a thing because what comes next is building the nest. And guess what this structure is made out of? That's right, mostly weeds. Grebe nests are cool because they demonstrate another adaptation to a highly aquatic lifestyle. The nest is actually a floating platform or mat made of aquatic vegetation.

So weeds like whatever slimy plants or algae the grebes find on the lake bottom or maybe some emergent plants that are growing in the shallows. And emergent plants, the ones that break through the surface, also serve as nest anchors. The nest does not drift around freely on the water. Instead, the grebes attach their nest to some cat tails or sedges or whatever. Because it floats on the water, a grieb nest is an inherently soggy place. The rim of the nest bowl typically rises only an inch or two above the water level. So the cup, or depression in the center of the nest, often sits slightly below the water line.

In that situation, which is fairly common, the eggs are constantly damp, with their lower halves typically resting in the water. It's amazing that this works, that the eggs don't drown or get too cold. In some species, like eard grebes, those nests are built in a colony, but there might be thousands of nests in a single colony. Whether in a colony or not, grebes tend to be highly territorial, especially around their nest site. For example, red-necked grebes are notorious for being super-agro. They're aggressive not just to other red-necked grebes that trespass the territory boundary, but to many other species as well. One aggressive behavior shown by red-necked grebes and some other species is called the sinister dive,

another great band name, or perhaps the name of a bar. And the sinister dive in grebes is also called the submarine attack. In this behavior, the rage-filled grebe sinks or dives beneath the surface. It swims under the intruder, and then it shoots up from out of the shadowy green depths like a nightmarish creature from the abyss. It jabs the intruder's belly with its sharp spear-like bill. In the case of red-necked grebes, ornithologists have observed them attacking other grebe species, a long list of duck species, loons, cormorants, coots, herons, and even, mammals like muskrats and meddling human researchers. Grieves typically have a clutch of two to seven

eggs. The eggs are initially pale blue or green, or they're that chalky white, but they usually turn brown because they get stained by the decaying plant material in the nest. When the parents need to leave the nest for a little while, they often hide the eggs under a layer of soggy vegetation. Pretty much all parental care is shared by the male and female. They both incubate the eggs and both feed the chicks. The eggs hatch asynchronously, in other words, not all at the same time. And what comes out are precocial chicks. They're covered in fuzzy down, their eyes are open, and they can swim.

However, their ability to regulate their own body temperature isn't great at first, and their down feathers are not waterproof. So to stay warm and dry, they need extra care from mom and dad in their, their first days after hatching. Not long after the last egg hatches, all of the little fuzzballs clamber onto the back of one of the parents. This is called back brooding, and we see it in some other types of water birds,

namely loons and swansers. Now, grieb chicks are, of course, really cute. In many species, their downy plumage has a bold pattern of black and white stripes, or some other bold pattern. After everyone has hatched, the family abandons the nest. One of the parents now acts like a mobile nest while the other parent forages for food. And remember that the parents will start feeding feathers to their chicks right away. Because you got to get that pyloric plug established, yo!

The chicks get ferried around on their parents' backs from one place to another, to places where they can then hop in the water to paddle around for some foraging of their own. As the parents are taking care of the chicks, they get even more aggressive toward other birds and mammals, the male especially. They defend a moving, floating buffer zone around their cluster of baby grebes. This zone can, for example, have a radius of about 130 feet or 40 meters. The duration that young grebes stay with their parents before becoming independent varies by species. It might be three weeks for one species, or three weeks. three months for another. For example, this period is pretty short in the eared grebe. Parental care

ends mostly at about 20 days after hatching. Western grebe chicks, in contrast, will keep being fed by their parents for about eight weeks, and even after that the family sticks together until the autumn migration. In any case, if mom and dad do a good job of feeding and protecting their young, and the little buggers don't get eaten by fish or turtles, then they head off into the world on their own. Although we don't have a lot of lifespan data for most species, it seems grebes are generally long-lived birds. Little grebes and eared grebes, for example, can live at least 12 to 13 years in the wild. And the great crested grebe has been documented living for almost 10 years. Despite their superficial resemblance to other birds living in similar environments,

grebes are a waterbird lineage that has gone off on its own path, with unique adaptations and a fascinating way of life. Adaptations that make a grebe a grebe. Like an arse-foot body structure with legs attached as far back as possible, lobed toes, fluffy butts without a tail, super-dense plumage, the habit of swallowing wads of furrow. feathers, a tendency to evolve toward flightlessness, building a floating nest, and those enthusiastic

synchronized dance moves during courtship. There are 19 grebe species out there in the world, and odds are that one or more can be found not far from where you are right now. So consider giving the next grebe you see a little extra attention and appreciation. Because, like I always say, to anyone who will listen, grebes are great. Thank you so much for spending time with me today to listen and learn about grebes. Even if you're a knowledgeable bird enthusiast or scientist, I hope you learned a new factor to, like how I learned what a tippet is. I want to give a massive thank you to all my supporters on Patreon.

If you don't know, Patreon is a membership platform where you can directly support the show with a small monthly pledge. In return, you get exclusive perks like a look behind the scenes, access to my community chat, getting to vote in polls, to choose episode topics, and more, all while directly helping me to keep making this show. So if that sounds groovy to you, please check out my Patreon page over at patreon.com slash science of birds.

The lovely humans who have joined my Patreon community most recently are Martin Beihauer, Lauren Tyson, Christy Morganstein, Mark Nimlose, Lara Hinchberger, Amy Moore, Andre Orchard, Adrian Jaggy, and Lynn. Sorry if I mispronounced your name there. Thank you all so, so much for the support. It makes a huge difference. It really, it makes all the difference. Anyway, if you have something you'd like to share with me, you can go ahead and shoot me an email. Perhaps you have a comment about the podcast.

Or you'd like to describe your territorial behavior in the face of an intruder. Is it anything like the sinister dive performed by grebes? In case you're wondering, my signature move when someone steps into my territory is called the screaming flail. I rush toward the intruder, emitting a blood-curdling shriek and swinging my arms around over my head like a psychotic orangutan. 60% of the time, it works every time. In any case, if you'd like to send me an email, my address is Ivan at Scienceofbirds.com.

Now, I'm still playing catch-up with my inbox, so I apologize if it takes a while for me to reply. This is episode 137. You can check out the show notes for the episode along with some Ivan-approved photos of grebes on the Science of Birds website, Scienceofbirds.com. And don't forget that you can pick up some t-shirts with my bird designs by going to birdmerch.com. So far, I've just got one grebe-related shirt, and the design is of a pie-to-build grebe. And you can check that out again at birdmerch.com.

I'm Ivan Philipson, and true fact about me, the only sport I got into in high school, in terms of being on an official team, was swimming. Several of my friends were already skilled accomplished swimmers, and I wanted to be part of the team with them. And then what ended up happening was that almost my entire social group joined. to the swim team when we were in 10th grade. So I certainly did not want to be an outsider, the one person who wasn't on the team. You know, FOMO and all that.

So I signed up. It was fun to spend so much time bonding with my friends, but yeah, I kind of hated swimming. I mean, don't get me wrong, I love water and I love goofing around in it, sort of like, you know, freestyle swimming on my own, like a frisky grebe, but being forced to swim laps back and forth

as fast as possible, feeling like I can't breathe? That was brutal, especially on cold mornings when we had to practice when the water wasn't heated. Anyway, I did it for two years. I'm glad I did and I have lots of fond memories, but I was so over it by senior year. But anyway, that's me. I wish you all the best and all the birds. Cheers.