The Science of Birds - Cormorants and Shags

Episode Date: July 3, 2024

In this episode—which is Number 99—we dive into the fascinating world of cormorants and shags, members of the avian family Phalacrocoracidae. These sleek, hook-billed birds are known for their distinctive silhouettes, often seen drying their wings on seaside cliffs or wetland trees. Cormorants and shags have a long history of varied human interactions, from being vilified and hunted to being revered and even trained to catch fish.These birds are exceptional divers, utilizing their streamlined bodies and webbed feet to hunt underwater. Their feathers are less waterproof than those of other aquatic birds, which aids in diving but necessitates their iconic wing-drying behavior. Cormorants can be found across the world, thriving in diverse habitats from coastal cliffs to freshwater lakes.They face significant conservation challenges. Human persecution and disturbances, habitat destruction, and climate change threaten several species, some of which are critically endangered.Links of InterestBrandt's Cormorants [VIDEO]~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

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 99. Today, we're talking about cormorants and shags. These are all the birds in the avian family, fallacro-coracody. Let me say that again, a little slower this time.

Fallacro-coracity. The word begins with pH. I know it's sort of a tongue twister, and honestly it's taken me a while to get used to it. Hopefully, you'll be used to it too by the end of this episode. These are sleek, dark, hook-build birds that stand on seaside cliffs atop wharf-pilings or among the branches of wetland trees in many locations around the world. Most of us are very familiar with the silhouette of a cormorant or shag, especially when they spread their wings to dry while perched. When I announced on social media that I was doing a podcast episode on cormorants and shags, I was pleasantly surprised at the outpouring of the outpouring of the world. of enthusiasm from my listeners. It turns out there's a lot of cormorant love out there.

And these birds need all the love they can get. Cormorants and shags have been vilified and persecuted by one culture or another, off and on, for thousands of years. For example, the Queen of England in the late 1500s, Elizabeth I, put out a bounty on cormorants. She called the birds, pests of the crown. In John Milton's epic poem, Paradise Lost, published in 1667, there's a passage that reads, quote, thence up he flew, and on the tree of life, the middle tree and highest there that grew, sat like a cormorant, end quote. And who was he? None other than Satan himself. Milton had the devil taking the form of a cormorant, not so great for cormorant public relations. On the other hand, some historical figures have actually admired cormorants and shags.

Elizabeth I's successors, King James and then King Charles, had some captive cormorants that were trained to catch fish. Fishing with these cormorants was a delightful activity enjoyed by the king. The birds were honored as the Royal Cormorants, with the capital R.C. And the guy who took care of them and trained them was the master of the royal cormorants. Now that's a fantastic title. I thought that the person who tends the ravens at the Tower of London had a cool title, Ravenmaster. But I think I'd rather be the master of the royal cormorants. Like I kneel in front of the king in his throne room and he taps my shoulders with his sword.

Then he says, I hereby dub the master of the royal cormorants. Arise. The building and ponds where the king's royal cormorants were housed happened to be just across the street from where John Milton lived. So that might be why a cormorant shows up in Paradise Lost. But these birds have been celebrated, or at least valued in other cultures too.

For centuries, people have used captive. cormorants to help with catching fish. In China and Japan, as well as in parts of Europe, fishermen would loosely fit tethered rings around the bird's necks, preventing them from swallowing larger fish. The birds go swimming around and they come back to the boat. The fisherman takes the fish out of the bird's gullet and later the bird gets a fish of its own to eat. So there's this long history of human cormorant relations. Some people think these birds are pretty much the devil incarnate, while others think they're pretty nifty and worthy of our admiration. The names Cormorant and Shag are somewhat interchangeable. In the British Isles

in Western Europe, where these words originated, there are basically just two species from this family, the Great Cormorant and the European Shag. Originally, these were just the Cormorant and the Shag. The word Cormorant comes to us for. Middle English, and before that, old French and medieval Latin. The original Latin name was Corvus Marinas, meaning sea raven. People used to think these birds are related to ravens and crows, so Corvus Marinas eventually transformed into cormorant. Shag refers to the tuft of upturned crest feathers on the heads of some species,

including the European shag. Sometimes the same species is called a cormorant in one part of its geographic range, and it's called by people in another region, shag. There is no biological distinction between what is or isn't a shag versus a cormorant. And speaking of biology, we better get to it. It's time to immerse ourselves in the biology of the family fallacro-coracity. First, let's consider what cormorants look and sound like, the body shape, the bills, plumage, voice, etc. And just so you know, when I say cormorants, I generally mean all the birds in this family, including the species we call shags. These are waterbirds, and so they have

streamlined sort of torpedo-shaped bodies that are perfect for diving. Their wings are somewhat short when compared to their body size. Cormorans don't use their wings much to propel themselves underwater the way penguins and puffins do. Instead, they use their feet for propulsion. But cormorants and shags can still fly. Well, all but one species anyway, and we'll get to that later. With their relatively short wings and heavy bodies,

cormorants spend more energy while flying than just about any other, kind of bird. The tail is wedge-shaped, and its feathers are stiff. It's used as a sort of rudder while the bird is swimming. The tail provides stability and control underwater. As you might expect, the feet are strongly webbed with skin connecting all four toes. Ornithologists call this type of bird foot, with webbing between all the toes, tote-to-palmate. Toto-palmate feet are great for zooming around in the water. The legs of cormorants are on the short side, but they're strong and sturdy. Cormorant beaks are really cool. They're long and thin with a wicked hook at the tip of the upper mandible. The bill in some species has a scaly-looking surface on its ramphothica. To me, this

texture gives the bird some reptilian flare. And remember that the keratin sheath on a bird's bill is what we call the ramphothica. The bill is generally black, gray, or buff colored in many species, but some have yellow, orange, or bluish bills. These colors are most obvious in the breeding season. The five species in the genus microcarbo are smaller birds and their beaks are stubbier than the birds in the other genera. And speaking of microcarbo, the world's smallest Cormorant species is microcarbo-pigmius, the Pygmy Cormorant. Its body is about 19 inches long, from beak to tail, which is about 48 centimeters. The title of world's largest cormorant is shared by two species, the Great Cormorant, Phallicro-Corax Carbo, and the flightless

cormorant, Nanopterum Heresai. These big boys are up to 40 inches or 100 centimeters long, so about twice the size of the pygmy cormorant. In terms of plumage and feathers, most cormorants and shags are dark birds, mostly black. But on close inspection, those black or dark gray feathers can have a beautiful iridescent sheen that looks bluish or greenish in the right light. A few species have plumage that's more brownish or gray, and nearly half of all the species have a white underside. The latter species are dark on the back, pale underneath. This pattern, like what we see in penguins and many other aquatic animals, is called countershating. Interestingly, it's only in the southern hemisphere that many Cormoran species have this two-toned coloration, with white bellies and

whatnot. Species in the northern hemisphere are more uniformly dark-colored. About half of the species in the family fallacro-coracity sport crest feathers, at least during the breeding season. These are the birds that put the shag in shag. This word comes from an old English word meaning rough matted hair. So that's also where the name shag carpet comes from, and I guess shaggy from Scooby-Doo. Double-crested cormorants, nanopterum aridus, grow long hair-like feathers on the two sides of their head during the breeding season, just above and behind the eyes. These crests look to me sort of like Muppet ears. The second part of this bird's scientific name is Alritis, that's A-U-R-I-T-U-S. That means having ears or eared. In some populations, these

crests are white, in others they're black. Cormorants are more than just monochromatic black or two-toned black-and-white beasts. The bare parts, in other words, the beaks, facial skin, throat pouches, eyes, and feet, these parts are quite colorful in many species. For example, the Pitt Island Shag has lime green and blue skin on its face. And then there's the aptly named red-faced cormorant. And the familiar double-crested cormorant of North America has bright yellow-orange skin on the throat and face in the breeding season. The eyes of a double-crested cormorant are absolutely gorgeous in the breeding season. They're a sparkling blue-green color.

To me, they're beguiling like living gemstones. And some other species have similarly beautiful eyes. Some species, mostly those in the genus Lucocarbo, have masses of warty, colorful skin on their faces. These structures are called caruncles. Caruncle is spelled C-A-R-U-N-C-L-E. The wild turkey is another kind of bird with warty skin like this. The Imperial Cormorant, also known as the Imperial Shag, lives in Patagonia and the Falkland Islands. This species has, in addition to bright blue skin encircling the eyes, a pair of large orange

caruncles jutting out in front of the eyes. These nasal caruncles become enlarged during the breeding season. Both males and females have them, and I'm sure the birds find them quite attractive. But if you opened your front door and you saw me standing there, smiling with a pair of orange caruncles growing on the sides of my nose, you'd probably take a step or two backward. You'd tell me to go see a doctor immediately and then slam the door on me. Wait, it's not a tumor! The iconic posture of a cormorant is the bird perched on a rock or tree branch, spreading

its dark wings wide for an extended time. You probably know what's going on here. The cormorant or shag is drying its wings after a swim. The birds tend to turn their backs to the sun and face into the wind. But why don't we see this same wing-drying behavior in the many other types of swimming birds? The reason is that birds in the family fallacrow caracity have feathers that are less waterproof than the feathers of other aquatic birds. Cormorant feathers have a unique structure that allows them to get partially wet.

We're talking about the contour feathers on the body. Research on great cormorant feathers revealed that they have a closed vein structure near the rachis, in other words the central shaft, which provides insulation and waterproofing. Meanwhile, the peripheral or outer parts of the feather vein are open and kind of messy, lacking interconnected barbules. This open structure in the periphery is responsible for the partial wetability of the feathers. Partial wetability is advantageous for a cormorant while it's diving. It reduces buoyancy and the amount of energy burned while diving. A bird that's partially waterlogged is apparently more agile and maneuverable while hunting underwater. Ducks, in comparison, have a closed

vein structure on the periphery of their feathers, and that structure allows water to roll off a duck's back. I used to think that the reduced waterproofing of cormorant feathers had to do with the secretions of their Euripigial gland, otherwise known as the preen gland. I thought that maybe these birds lacked such a gland, or the oils from their gland were less effective or something. But cormorants and shags do have Euripigal glands, and research has shown that these glands are are probably fully functional. The wetability of phallicro-caracid feathers has much more to do with feather structure

than with the euripigial gland. How deep a cormorant or shag dives, and for how long each time, varies among species, and dive depths depend on other factors like the time of day. It's probably fair to say that typical dive depths for birds in this family are between 15 and 100 feet, or 5 to 30 meters.

Typical dive duration is about 30 seconds, but can sometimes be well over a minute or two. While paddling around on the water's surface, Cormorants sit low in the water, because they're not all that buoyant, right? Sometimes all you can see above the water line is the bird's S-curved snake-like head and neck. Now, I just double-checked,

and it appears that both the Great Cormorant and the European Shet, have been observed swimming around in Loch Ness, in Scotland. The birds are rare on the lake, but it's not unheard of. So I think I've solved the mystery of the Loch Ness monster. You know that famous black and white photo of Nessie, where the creature is just a dark silhouette with its long neck sticking out of the water? Uh-huh.

Cormorant! Nessie is a Cormorant. Case closed. And if you were to hear the haunting cry of the Loch Ness cormorant while standing on the lake shore on a gloomy evening, it would probably sound something like this. Birds in the family fall of the great cormorant. aren't all that vocal, as birds go.

The sounds they do make are mostly grunts, croaks, and hisses. Here, for example, is the fantastic croaking sound of a double-crested cormorant. It kind of sounds like that cormorant was belching after chugging a liter of Pepsi or something. A close cousin of the double-crested cormorant is the neotropic Cormorant, nanopterum Brazilianum. The latter species makes deep grunting calls. They sound like frogs or pigs, like this. People in Mexico and other Latin American countries have special names for neotropic cormorants.

Names like pato serdo, meaning pig duck, and pato chiroch. and Pato Chancho, meaning dirty duck. Now, let's go all the way over to Russia, to the mouth of the Volga River on the northern shores of the Caspian Sea. This is the raucous sound of a great cormorant colony in the River Delta. Moving on to discuss the diversity, distribution, and habitats of birds in the family fallacro choracity. First, let's take a moment to consider the meaning of this tongue-twisting family name.

Its origin is ancient Greek. Phalachros means bald and corax means raven. Put them together and you get a bald raven. I guess the bald part actually refers to the bare facial skin of some species. The root word carbo, C-A-R-B-O, shows up a lot in the scientific names of these birds. For example, the great cormorant is phallicro-corax carbo. And there are the genera microcarbo and leukocarbo. Carbo is derived from Latin, where it means coal or charcoal, as in carbon, right?

And as in carbohydrates, the molecules that have carbon atoms in them attached to hydroton atoms. Anyway, many species of cormorants and shags have predominantly black or dark plumage reminiscent of coal or carbon, and so there you go. Right, so let's sort out where our phallicrochoracids belong, on the avian tree of life. On what branch do they perch, like Satan perching in that other tree of life in Milton's Garden of Eden? The family phallicro-coracity is part of a large branch sometimes called the water birds. Other families on this branch include loons, storks, herons, ibises, and pelicans. But the birds most closely related to cormorants are the four Anhinga and darter species. These are all in the family Anhingadi. One name for this group is

the snakebirds. I'll make a podcast episode about them someday. Anhingas and darters look a lot like cormorants, but they're more stretched out and sleek. They have pointy, stabby bills instead of hooked bills. But birds in the family in hingadie also hold their wings out to dry in the air, just like cormorants. The two families share the trait of having feathers that get partially soaked during dives. Another feature shared by cormorants and darters is the occipital style, a thin, pointy bone that sticks out from the back of the skull. This bone is unique to these two bird families. With their strong and flexible necks, these birds can strike quickly and accurately at fish underwater. The occipital style, also called the nucal bone or the os nukaly, provides the attachment point for

certain neck muscles used in these rapid and precise movements. The next most closely related bird families to the cormorants are, one, sule di, the boobies and gannets, and two, fragatidae, the frigate birds. The four families, phallicrocarasidi, and hingdi, suleady, and fragotidee, together these make up the avian order Sulaformis. Turning our focus back to just the Cormorant family, some scientists back in the 1970s and 80s split the group into two sub-families, one for the cormorants and one for the shags.

This classification was based on behavior and physical traits like skeletal structure. Using DNA for classification wasn't really a thing yet back in the 70s and 80s. But it turns out those sub-families, and the idea that cormorants and shags belonged to two independent lineages, that was all lies, man, it ain't true. Research over the last ten years or so has gotten us closer to the truth. It's helped us sort these birds out.

Modern genetic analyses using DNA have revealed the existence of seven genera in the family phallicro-coracity. There are about 40 species of cormorants and shags worldwide, and most of them belong to either the genus fallacro-corax or the genus Lucocarbo. Depending on the field guide or website you're looking at, you may find these birds to be classified differently. As always, I use Clemens' checklist of birds of the world, which is the taxonomy used by e-bird and the Cornell Lab of Ornithology. Species in the family phallicro-coracity are found worldwide. They're on every continent. Well, every continent except for my old nemesis, Antarctica. As with so many other kinds of birds, there are no cormorants.

Wait, no. My bad. Just looking at my notes here, I had just assumed because, you know, Antarctica. But it turns out there are cormorants on that dreary, desolate continent. In fact, there's a species called the Antarctic Cormorant, Leucocarbo Bransfieldensis. Also called Antarctic Shags, these birds live on the northern half of the Antarctic Peninsula. And amazingly, they're year-round residents there.

Hmm, maybe Antarctica ain't so bad after all. I mean, if the shags are into it. Now let's do a quick world tour of the other continents. North America has six species. And far in a way the most common of those is the double-crested cormorant. Similarly, and fitting given its name, the neotropic cormorant vastly outnumbers the five other species in South America. The Great Cormorant is by far the most commonly observed species in Europe, which is one of three species that regularly occur there. The Great Cormorant is actually the most widespread member of this family.

It's found in many places across the old world. Africa has about seven species. The two most common on that continent are the long-tailed cormorant and the Great Cormorant. The Great Cormorant wins the prize once again in Asia, where it is the most frequently recorded species among the 11 species that occur there. There are about 15 species in Australasia, with the little pied Cormorant being the most common. That species lives across a large portion of Australia, New Zealand, Indonesia, and some of the Pacific Island nations. New Zealand and its outlying islands actually make up a hot spot of diversity for these fallacrochor acids. There are 12 species in New Zealand, including the spotted shag, Stewart Island, Shag, Auckland Islands, Shag, and Pied Cormorant.

Not to be confused with the little pied cormorant I mentioned a moment ago. There are also a bunch of species strewn across islands in the southern seas, the South Atlantic, Indian Ocean, and South Pacific. Many of these are closely related species in the genus Lucocarbo, and many are confined to just one island or a small cluster of islands. The 15 leukocarbo species diversified over the last 7 million years or so from a single common ancestor by setting up isolated colonies, on far-flung islands in the chilly southern seas.

These are all the black and white cormorants slash shags that have funny crests and, in most cases, caruncles on their faces. Lucco-carbo translates as white-black, or white-and-black, I suppose. Weirdo alert. Weirdo alert. Uh-oh, it's time to look at the weirdest weirdo. in the family phallicro-caracity.

Maybe it's no surprise, but the flightless cormorant gets this honorable distinction. Nanopterum Heresai, the flightless cormorant, is found on just two of the Galapagos Islands in Ecuador. It's a chunky bird, with plumage that's uniformly brownish-gray or sometimes black. So it's not a colorful bird, but it does have lovely blue eyes. Breeding and feeding among dark volcanic rocks along the shore, flightless cormorants dive in cold water to hunt for fish, including eels and rockfish. They also eat octopuses and squid. Remember that this is pretty much the largest member of the family Fallacro Coracity.

I didn't mention it earlier, but male and female birds in this family are generally indistinguishable to us humans. That said, males are sometimes slightly larger, but in the flightless cormorant, males are about 35% heavier, than that's pretty significant. The lack of land-dwelling predators in the Galapagos Islands is probably what allowed the ancestors of the flightless cormorant to gradually lose the ability to fly. Flying takes tons of energy. If you don't need to fly, you could use that energy instead for things like making lots of

baby cormorants, and for living a fat and relatively carefree island life. I did an entire podcast episode about the evolutionary phenomenon of flightlessness in birds, so check that out if you haven't already, and you'd like to learn more. The flightless cormorant is a close relative of both the double-crested and the neotropic cormorant. These three birds diverged around two million years ago, and are the only species in the genus nanopterum today. This word is from Greek and it means small wing. And indeed, the flightless cormorand has itsy-bitsy wings. But these birds still hold their scrappy little wings out to dry after a swim. It's pretty adorable. I mean, do they really need their wing feathers to dry out

anytime soon? It's not like the bird is going to need dry wings to fly. Now, I could be wrong, but I'm guessing this is mostly a sort of vestigial behavior. A holdover, an adivism, from those long-gone days when cormorants in the Galapagos Islands could still fly. Most cormorant and shag species are non-migratory. In other words, they're relatively sedentary or resident birds. But some, like the double-crested cormorant and great cormorant, have populations that do migrate. Double-crested cormorants that breed in the interior of North America, for example, are strongly migratory. During the non-breeding season, they move to the southern U.S. along the Gulf of Mexico, or further south into parts of Mexico, Central America, and the Caribbean. Cormorants are highly adaptable and can be found in diverse habitats, as long as there's some water around for splishing and splashing.

We find cormorants and shags on marine coastlines, in estuaries, and in freshwater lakes and rivers. They typically prefer areas with abundant fish and suitable roosting or nesting sites. Coastal birds spend more time on rocks and cliffs, whereas inland birds hang out on trees more often. In many places around the world, two or more species in this family live side by side. One word ecologists use for a group of closely related co-existing species is an assemblage. The species in a cormorant assemblage all eat fish, so it seems possible that they would compete for that food, and maybe for things like nesting sites too. Researchers have been trying to understand how multiple cormorant and shag species can coexist like this.

How can one ecosystem support two or more of these species, which might be competitors? More research is certainly needed, but it seems that, in some cases, the different cormorant and shag species living together forage in different habitats, and they may eat different fish species. For example, in one study on the coasts of Western North America, double-crested cormorants were found to prey on schools of fish in the watercolumn. where the bottom is flat sand or mud. But in the same waters, pelagic cormorants chased solitary fish in rocky areas. So the two birds don't necessarily need to compete for prey. Some people think cormorants look like prehistoric creatures. Creatures like, you know, the Loch Ness monster. That isn't surprising, given these birds snake-like necks, beguiling eyes, and scaly beaks.

Cormorants have certainly been around a long time. Scientists estimate that the fallacro-caracity lineage was already well-established by about 30 million years ago, during the Oligocene epic. Some research suggests that fallacro-caracity and its sister family and hingady split over 40 million years ago. The geographic origin of the family phallicro crassity is less clear. The oldest fossils in this lineage are from the late oligocene of both Europe and Australia. That's such a broad geographic spread that it doesn't give us much insight into where these birds came from. It seems that by the late oligocene, cormorants were already splashing around in the coastal waters across much of the old world. So, if nothing else, maybe we can assume reasonably that these birds originated somewhere in that half of the planet.

As I mentioned earlier, recent studies using genetic data have sorted the 40-ish cormorant species into 7 genera. This comes mostly from a paper published in 2014 in the journal Molecular Phylogenetics and Evolution. Of the 7 genera, it looks like microcarbo is the most ancient. the most basal. This lineage of fun-size, adorable species that we sometimes call the lesser cormorants was the first to split off from the other cormorants. And that happened about 13 to 15 million years ago. A study from 2023 focused on the evolutionary genetic relationships among the five microcarbo cuties, so just within that one genus. It concluded that the two microcarbo species in Africa, the long-tailed cormorant and the crowned cormorant, are so distinct

that they deserve to be in their own genus. The ancestor of these two species appears to have split from the other microcarbo birds around 12.2 million years ago. The researchers who made this discovery proposed the name Afrocarbo for the new genus. Now that I know of, this new classification has yet to be incorporated into any of the major bird taxonomies. But this is a very recent study, so that's not surprising. These things take time. Maybe phallicro-coracity will someday have eight genera, including afrocarbo. Let's turn our focus now to the conservation status of cormorants and shags.

Many species seem to be doing reasonably well, but some face serious threats and are at risk of extinction. In terms of the IUCN Red List threat categories, there are seven species in the vulnerable category, including the flightless cormorant. Three species are in the endangered category. These include the Bank Cormorant and Cape Cormorant, both from southern Africa. The third endangered species is the Pit Island Shag. That's the species I mentioned earlier that has lime green facial skin. It lives only on the Chatham Islands of New Zealand. Then in the same group of small islands, we have the actual Chatham Islands shag,

Leucocarbo-onsloi. This is the world's most threatened member of the family phallicro-coracity. With only about 1,000 individuals living on a couple of small islands, this species is in the critically endangered category. Colonies of this bird on Chatham Island face threats from invasive predators like feral cats and possums. Disturbances by people and livestock sometimes cause birds to abandon their nests. This leads to egg breakage or predation by gulls, and entire colonies have been deserted because of disturbances like this. Climate change, with rising sea levels and weather anomalies, is another factor that endangery.

the Chatham Islands shag. Threats like these, invasive species, disturbances by humans, and climate change are affecting many other declining cormorant species. On top of all that, there's habitat destruction, pollution, overfishing, and oil spills. And as I mentioned earlier, cormorants of one species or another have been outright persecuted by many people. The birds are sometimes killed by the hundreds or thousands. or thousands. Killings are illegal in some cases and officially sanctioned by the government in other cases. The most zealous persecution of cormorants occurs to this day in North America and Europe.

In North America, our most common species again is the double-crested cormorant. This species suffered major population declines in the first centuries after European colonization, because of habitat loss and persecution. It was also hard hit by the effects of the insecticide DDT in the middle of the last century. But after DDT was banned and the birds became protected under the Migratory Bird Treaty Act, double-crested cormorants made a miraculous recovery. As their numbers swelled, however, the birds came into conflict with people more and more. They eat fish and people who depend on fish for a living or who like,

to go fishing for fun, well, some of those people see cormorants as a scourge that needs to be wiped out. For example, in 1998, a handful of fishermen living on the shores of Lake Ontario in New York took violent action against the cormorant colony on Little Galu Island. The fisherman illegally shot at least 1,000 cormorants, including helpless chicks. But the actual number of birds slaughtered might have been as high as 20,000. These fishermen dudes, who were apparently proud of their murderous rampage, were members of an activist group calling themselves concerned citizens for cormorant control. In the years since, government agencies in North America have tried to manage double-crested cormorant populations. They sometimes go out and

shoot the birds or spray their eggs with oil. The chick inside an oil covered egg suffocates, since oxygen and carbon dioxide can no longer pass through the shell. These government agencies are trying to appease the interests of the fishing and aquaculture industries, as well as those of conservation groups. And that's not a simple thing to do. It seems like kind of a mess to me. For example, there was the East Sand Island debacle that happened right here in my home state of Oregon. East Sand Island, a 62-acre glorified sandbar near the mouth of the Columbia River, once supported North America's largest double-crested cormorant colony. At its peak, the colony had about 30,000 birds. But government agencies, particularly the U.S. Army Corps of Engineers,

have identified the cormorants as significant predators of threatened salmon species in the Columbia River. The government argued that cormorants were scarfing down millions of juvenile salmon every year, contributing to the decline of these fish populations. So the Army Corps of Engineers proposed and implemented lethal control measures to reduce the cormorant population on East Sand Island. These actions eventually led to the complete collapse of the cormorant colony on the island. One day in 2016, the remaining birds all just took off and didn't come back. Many of them moved downstream and set up shop on the massive bridge that spans the mouth of the Columbia.

The culling of cormorants by the government sparked a major backlash from conservation groups and bird enthusiasts. Conservationists argued that killing cormorants was an inhumane and ineffective solution to the salmon crisis. After all, there are broader issues affecting salmon survival, such as habitat destruction, overfishing, invasive species and hydroelectric dams. Cormorants just make convenient scapegoats for problems that humans are actually responsible for. Many argue that the money and resources used to kill and harass cormorants could be better spent elsewhere if the goal is to protect salmon. Yeah, what a mess, right?

You're trying to protect one group of endangered animals, the salmon, by killing another group of protected animals, the birds. and you're trying to satisfy the demands of all these stakeholders, demands that are often in complete opposition. And now it sounds like the local government is thinking about trying to re-establish the East Sand Island colony. So that's kind of ironic, I guess. In any case, scientists aren't even sure what the long-term ecological effects of Cormorant culling might be. How much do cormorants really affect fish population?

in places like the Columbia River or Lake Ontario. Sometimes cormorants are actually helping because they're eating invasive fish species that humans introduced. There was a paper published in 2020 that looked at the effects of cormorants around the world on fish populations. This was a meta-analysis.

I'm not sure if I've explained this term before on the podcast. A meta-analysis is a statistical technique used to combine and analyze data from multiple independent studies on a specific topic or research question. The purpose of a meta-analysis is to synthesize findings from different studies to identify overall trends, patterns, and effects. It's sort of like a review, but backed up with special statistical analyses. Anyway, this global meta-analysis from 2020 looked at the impact of Cormorant predation on fish and found that, yes, Cormorant predation does have a negative effect on fish populations overall.

But this effect was not statistically significant. Now, there are many nuances and caveats with this kind of study, but I guess the important takeaway is that it did not find overwhelming evidence that cormorants are devastating to fish populations. To me, it seems like we should pull. point the finger at ourselves, rather than go on a witch hunt to kill cormorants. I know that this is a highly complex issue, and it's not like I can offer a magical solution. But hey, I'm a bird guy, so I tend to advocate for the welfare of my little

feathered buddies. But perhaps you disagree with me. Maybe you think of cormorants as little devils, as vermin that deserve extermination, and listening to this podcast episode so far, sadly, has not changed your opinion. Now, before you write me some hate mail, spewing anti-Cormorant vitriol in my direction, let's make sure you have my correct email address. Grab a pen and paper. Okay, my address is Cool Guy 1987 underscore TGIF at pentagon.gov. There's one more species I want to mention in the context of conservation. It's Palaces Cormorant, Urily, Perspyssalius. Palace's Cormorant was a behemoth among its kind, one of the largest cormorants ever known.

It was goose-sized, weighing up to 14 pounds or 6.4 kilograms. Its impressive size was complemented by dark plumage, crest feathers on its head, and distinctive white facial markings around its eyes, giving it a spectacled look that set it apart from other cormorants. Another common name for the species is spectacled cormorant. Pallas's cormorant made its home on Bering Island, off the east coast of Kamchatka in Russia.

These birds thrived along the coast, diving into the icy nutrient-rich waters teeming with fish. And notice I've been talking about this bird in the past tense. Tragically, Palis's Cormorant went extinct around 1852. Several factors contributed to its demise, but human hunting was the biggest problem. The birds apparently had no fear of humans, and some researchers think it was also flightless,

or almost flightless. In any case, these birds, like the ill-fated dodoes of Mauritius were easy pickings. Russian settlers and fur traders and native people hunted Palaces Cormorants for their meat and their feathers. The introduction of invasive species like rats and mink also threw some wrenches into the gears of the island's ecosystem. With a limited range confined to a small geographic area, Palaces Cormorants were exceptionally vulnerable to environmental disruption like this, and to human activities.

So this is the one Cormorant species that has gone extinct at the hands of humans, at least that we know of. Its closest living relative is probably Brant's Cormorant, Urily Penicillatus. Cormorants and shags are primarily piscivorous birds. That means they eat mostly fish, right? But coastal dwelling species will also hork down crustaceans like crabs and shrimp, and cephalopods like squid and small octopuses. Some cormorant species will also eat frogs and other amphibians in freshwater habitats,

as well as lizards or the occasional snake or even a stray rodent, because these birds are opportunistic feeders, eating many kinds of aquatic prey, as well as small terrestrial animals that are loitering around on the shore. The double-crested cormorant, as an example, eats mostly fish. But it's not picky. Over 250 fish species have been documented in the diet of this bird. One of the primary ways scientists figure out what cormorants have been eating is by analyzing

their barf. To feed their chicks, or as a disgusting defense against predators, cormorants around the world will cough up objects called regurgitants. These are partially digested wads of fish parts and whatever else the bird had for lunch. Cormorants also hack up pellets, similar to what owls do. Pellets are formed from the compacted indigestible parts of their prey, like bones, scales, and exoskeletons. Researchers interested in cormorant diets collect and pick apart these regurgitants and pellets. The cormorant bill is well adapted for catching and holding on to slippery fish.

The sharp hook at the tip, what we would call the nail, helps them grasp their prey securely. These birds can also raise their upper beak independently from the lower beak. Remember what this ability is called? It's not unique to cormorants, but not all birds can do it. It's called rinkgo-kinesis. In cormorants, there's this nimbus. nasal frontal hinge at the base of the upper bill, where the nasal bones meet the frontal bones of the skull. The hinge allows a cormorant to open its jaws extra wide. All the better for

grabbing onto a wiggling fish. And all the better for eating a fish that seems to be way too big for the bird to swallow. If you do some Google image searches of cormorants eating fish, you're going to come across some ridiculous examples. Cormorants can expand the skin of their guler sacks, in other words, their throat pouches, to let enormous fish slide down their gullets and into their stomachs. No wonder people have portrayed cormorants as symbols of greed and gluttony. But that's not really fair. I mean, cormorants aren't any more gluttonous than other seabirds. They need to eat the same way we do. And cormorants are opportunistic. If one gets lucky and catches a jumbo-sized fish, why not try to gulp it down? That would be more energy

efficient than having to get the same number of calories by catching several smaller fish. Cormorants and shags are superb divers. Many of them, when paddling around on the surface, make a funny sort of half-jump as they take the plunge. Then they use their powerful legs and feet to propel themselves under water, as we discussed earlier. They sometimes use their wings underwater, too, to maneuver while pursuing prey. Earlier, I said that typical dive depths for phallicrochoracids are between 15 and 100 feet, or 5 to 30 meters, and the typical dive duration is maybe 30 seconds. But some species dive deeper and for longer durations.

For example, there was this recent paper published in the journal Ploss One. It had a great title, Selfies of Imperial Cormorants, What is Happening Underwater? In this study, male Imperial Cormorants in Argentina were fitted with miniature video cameras to document their dives. There were 12 individual birds, and they made 49 dives over the course of the study. The average dive depth was 145 feet or 44 meters. Average dive duration was 2.86 minutes. But earlier studies apparently found that the Imperial Cormorant can dive even deeper,

down to about 330 feet or 100 meters. The video footage in this selfie study revealed that Imperial Cormorants are primarily bottom feeders, using a prey flushing technique to capture fish at short distances. Interestingly, the study found that cormorants often forage in fairly dark environments, and this suggests that they may rely on senses other than vision to locate their prey. And yeah, apparently, and shockingly, cormorants in general don't see all that well underwater. They seem to have poor underwater visual acuity. For example, great cormorants have been shown to have underwater visual acuity comparable

to what you or I would see underwater without goggles or anything. I don't know about you, but when I open my eyes underwater, everything is pretty blurry. I might be able to catch a fish if it was right in front of me. And assuming I had a long, hooked beak, an occipital style at the back of my skull and lightning quick reflexes. But seriously, that may be how cormorant foraging works, at close range. Again, research on great cormorants found that these birds are able to detect prey only if it's within about three feet or one meter.

Some other research supports this idea. Great cormorants adjust their diving depth based on light levels. During bouts of hunting at dawn and at night, when light levels are lower, the cormorants dive to shallower depths. In contrast, during the daytime when light levels are higher, and it should be easier to see, they dive deeper. We come at last to the subject of breeding in cormorants and shags. These are monogamous birds. A mated pair will stick together for at least one breeding season.

It's my understanding that it's less common that the pair would reunite for multiple seasons. seasons. The male performs a courtship display to convince a potential mate that he is her best option among many. The courtship display varies among species, but there are some common features. Males of many species spread their wings, raise their tails, fluff up their crests, and rear their heads over their backs, and or they dip their heads forward. They flash their colorful facial skin, especially the Guller's sack just below the chin. Brant's Cormorant, for example, has an electric blue Guller Sack, which features prominently in this species courtship display. So the Guller Sack has more than one function in the life

of a cormorant, right? It expands to swallow or temporarily store fish and other prey, and it can be a sexual signal during the breeding season. The Guller Sack can also help a cormorant cool off on a warm day. The skin of the throat is criss-crossed by lots of capillaries close to the surface. With its mouth open, the bird rapidly expands and contracts its guler's sack, moving air over the skin of the throat and the inside of the mouth. This behavior is called gooler fluttering. That movement of air across the guler's sack skin dissipates heat and helps the bird cool down. It's like panting and dogs. Anyway, we were talking about courtship displays.

Species like the double-crested cormorant also have a recognition display, performed by both sexes. The birds open their mouths wide toward each other, and this shows off the vibrant blue skin lining the inside of the mouth. The birds move their necks around slowly while calling to each other. Cormorants typically nest in colonies. These could be on cliffs, trees, or the ground, but pretty much always near water. Colony size varies by species, by population, and by location.

Species like the Little Pied Cormorant nest in trees or shrubs, and their colonies may contain no more than a few dozen individuals. Other species like the Guanae or Guanae Cormorant, which lives on the Pacific coast of South America, can have colonies with hundreds of thousands of birds. Here's a recording made in a Guanae Cormorant colony. Cormorant nests are typically bowl-shaped. They're made of sticks, seaweed, grass, and odd bits of whatever's lying around. Old fishnets, trash, the carcasses of dead birds. Seriously, double-crested cormorants. will sometimes toss the desiccated corpse of a fallen comrade on their pile of nest material.

Both the male and the female share in the work of building their nest. Sometimes a cormorant will waddle over to its neighbor's nest and steal a beak full of nest material. For this reason, perhaps, and because quality nest sites are generally valuable, cormorants defend the small territory around their nest from interlopers. guano cormorant poop is used like cement in nest construction the birds blast excrement onto the sticks and seaweed to bind everything together or guano may be used to build a sort of foundation a raised platform upon which the birds can build their nest on some offshore islands and coastal cliffs guano at a colony site has been accumulating for centuries building up deep layers of the stuff in peru and Chile, for example, humans have been harvesting guano as a natural source of fertilizer for thousands of years. The species that these South American chaps have been getting their fertilizer from is none other than, I'm sure you can guess, the guanai or guanet comerant, luco-carbo-buganviliy. Gwanae is spelled

G-U-A-N-A-Y, and if you know the correct pronunciation of that, please let me know. And this got me curious, so I looked into it. This name comes from the South American Spanish word Guane, G-U-A-N-A-E, which itself might have come from the word Wones, the plural form of Wano, H-U-A-N-O, meaning Dung or Mnuer. And going back even further, the Spanish word Wano came from W-A-N-U, which is the indigenous Ketchua language word for dung. So Wano became Wano, which gave us the word guano on the one hand, and the plural form was Wanase, and that gave us guane ending with A-E, and finally we got Gwane ending with A-Y as the name of the bird. The ways words and languages evolve like this is pretty wild, and thanks for indulging me there with that tangent.

And I wonder if Guanae cormorants would be offended if they could understand that we've named them after their own poop. It's kind of like naming your baby boy, turd Ferguson or something. Anyway, cormorants in general poop so enthusiastically at their colony sites that they often damage or kill trees and other plants that get covered in guano. Bird poop is pretty corrosive stuff after all. It'll eat through the pain on your car if you let it. Double-crested cormorants nesting in trees may kill those trees with the whitewash of their cost. excrement. The birds, having done their damage, may just pack up and move their breeding activities elsewhere. Cormorant and shag eggs are typically white or pale blue with a chalky surface

texture. Clutch size is normally two to four eggs, but it can be up to about seven. Like many other seabirds, cormorants have asynchronous hatching. The eggs are laid over several days, usually with one egg laid every one to two days. As soon as the first egg is laid, the parents begin incubating it, even though more eggs are still coming down the pipeline. This results in a staggered start to the development of each egg. So the eggs hatch asynchronously. The first egg to be incubated will hatch first,

followed by the second, third, and so on. The older, larger chicks often out-compete the younger ones for food. However, in times when there are plenty of fish in the sea, so to speak, even the youngest chicks can survive and thrive. There's enough food for everybody! A parent returning to the nest is like Oprah giving away cars. You get a fish, you get a fish, you get a fish, and you get a fish! In lean years, however, only the oldest, largest chicks are likely to survive.

From the perspective of the parents' reproductive output, it's better to have one or two chicks survive than none. Both parents take turns incubating the eggs and feeding the chicks once they hatch. Incubation takes three to four weeks. The young are altricial, meaning they are born helpless and require significant parental care before they can fledge. Baby cormorants hatch without any feathers. Their naked skin is dark or light, depending on the species. With their jerky movements and incessant begging calls, the hatchlings are, one could argue, kind of cute. In the same way, I suppose, that the gremlin-like Muppets from Jim Henson's dark crystal movie, with their jerky movements and creepy little faces were cute.

For ground nesting cormorants, the chicks will eventually leave the nest and gather into groups called Creshes. Cresh is spelled C-R-E-C-H-E, but a chick will waddle back to its parents to get fed. The youngsters fledge when they're somewhere between 50 and 80 days old. Mom and dad will still care for them for a few more months after fledging. Cormorants and shags are somewhat long-lived birds. They have been known to live for several decades in captivity. In the wild, however, they're more likely to live 10 to 15 years. And these birds are generally what we would call philopatric. They tend to return to the colony where they were born,

and adults faithfully return to the same colony site year after year to breed. My hope is that by listening to this podcast episode, your appreciation for cormorants and shags has ticked up a few notches. These are really cool and interesting birds. They have many amazing adaptations to their aquatic lifestyle. They have fascinating behaviors, and they're just funny and charming all around. Sometimes, just by paying closer attention, we can find beauty in something that others have overlooked or willfully ignored. So maybe you can take a closer look the next time you run into some cormorants.

these so-called bald sea ravens, these dirty ducks, these croaking, fish-gulping, partially wettable pests of the crown. That wraps up episode 99 of the podcast. I hope you enjoyed listening to it as much as I enjoyed putting it together for you. When I announced the topic of this episode on Instagram, my favorite comment was, Oh, heck yeah, Cormorant Squad, rise up. That was fantastic. It was so great to see the joy and excitement about this group of birds. I have the best listeners in the world. Seriously.

And the best of the best among my listeners are those of you who are supporting members of my Patreon community. You guys have made all of this possible. Thank you so much. And a special thanks to those of you who recently jumped on board to provide support. Welcome to Ilona, Lynn Lozier, hope I said that right, Mark Toole, VJ Teague, Robert Mercer, Sue, and Aaron Fitzgerald. Thank you all. I am honored by your support. Anyone else who would like to help out the show can just hop over to patreon.com slash science of birds. And if you have a few words you'd like to share with me, go ahead and shoot me an email.

Maybe you have a pithy comment about the podcast. Or you'd like to share your theories about the Loch Ness monster. In any case, my address, the real one, is Ivan at Scienceofbirds.com. Again, this has been episode 99. You can check out the show notes for the episode, along with curated photos of some cormorant and shag species I talked about today on the science of birds' website, scienceofbirds.com. I'm Ivan Philipson.

Thanks for listening to me rant about cormorants today. and I'll see you next time. Cheers.