The Science of Birds - Great Blue Heron

Episode Date: February 13, 2023

This episode—which is Number 70—is all about the Great Blue Heron. The scientific name for the Great Blue Heron is Ardea herodias.This species is one of the most familiar large birds in North America. So it was inevitable that I’d make a podcast episode about it.The Great Blue Heron is a beautiful, fascinating, and ecologically important bird.Links of Interest‘Great Heron’ sculpture by artist Dixie Friend GayGreat Blue Heron: Nesting and Mating Behavior [VIDEO]Great Horned Owl attacks Great Blue Heron in Sapsucker Woods [VIDEO] ~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

Not long ago, I was enjoying a little birding in southern Texas. There I was walking along the coast near the city of Corpus Christi when I had an encounter with a great blue heron. The experience left a lasting impression on me, because this bird was enormous. It towered over my head, standing about 20 feet tall. Yes, you heard me right, 20 feet tall, which is about 6 meters. Now, don't worry, I haven't lost my marbles, and I'm not going to suddenly turn this into a silly crypto zoology podcast, where I talk about bigfoot, chupacabra, and giant birds that don't exist. This great blue heron I encountered in Texas wasn't a real bird. It was a massive metal sculpture. Created by artist Dixie Friend Gay, it stands guard at the entrance to the Osobay

wetlands preserve in Corpus Christi. The sculpture impressed me because it shifted my perspective dramatically. I felt small and vulnerable as I looked up at it. A Tyrannosaurus-sized heron like that, if it were alive, would see me as an easy meal. Now I can imagine just how terrifying a great blue heron must be to fish and many other small animals. We humans are lucky that these herons stand only about five feet tall, rather than 20. And we're lucky to have these wonderful birds in North and Central America, stalking around in our wetlands and along our seashores. Because the great blue heron is a beautiful, fascinating, and ecologically important bird. Hello and welcome. This is the science of birds.

I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted exploration of bird biology for lifelong learners. This episode, which is number 70, is all about the Great Blue Heron. The Bird, that is. Just to be clear, we're not talking about the Great Blue Heron casino and hotel in Toronto, Canada. If you're here to listen to a podcast episode about a casino, well, I'm sorry to disappoint you. Also, you might have a gambling problem. But hey, if you'd like to learn about a cool bird, stick around, my friend.

The scientific name for the Great Blue Heron is Ardia Herodias. This species is one of the most familiar large birds in North America. So it was inevitable that I'd make a podcast episode about it. But the reason the episode is dropping today, rather than months or years from now, is because my supporters on Patreon voted to make it so. I ran a poll on Patreon, asking my patrons to vote on which bird species episode 70 would be about. The choice was between the Great Blue Heron and the red-tailed hawk. Both birds are awesome, of course, and both are common in the U.S.

but I had no idea which of them would win the poll. The heron ended up with 53% of the vote and the hawk got only 47. The red-tailed hawk will get its day in the spotlight here at some point. But today it's all about the heron, the GBH, as many people like to abbreviate its name. kicking things off with the basic traits of the great blue heron, what this bird looks and sounds like. Like many other large herons and eagrots, the body shape of the great blue heron is, in a word, elongated. It has a long neck and long legs. Beak to tail, the species ranges from 38 to 54 inches or 97 to 137 centimeters. There are about 633,000. There are about 63,

species in the heron family are deity. But the great blue heron is one of the largest. Only the Goliath heron and white-bellied heron are taller. So the G.B.H. is large for a bird, and it's also large compared to most other herons. But because of its many weight-saving adaptations, a great blue heron weighs only about five pounds, which is roughly 2.7 kilograms. Just five pounds. That's hard to believe when you look at one of these birds. When resting, the heron can tuck in its neck, taking on a more compact, hunched over sort of appearance. Some say a great blue herons standing like this at the water's edge on a foggy morning looks like an old man wrapped in a cloak. When flying herons typically fold up their necks in an S shape. That's one way

to tell a flying heron apart from a flying crane at a distance, because cranes fly with their necks outstretched. The great blue heron's neck has something like 20 vertebrae. If you listen to my last podcast episode, which was about the avian skeleton, you'll remember that the neck bones are called cervical vertebrae. Well, I couldn't find the exact number of cervical vertebrae in our heron. Even after spending way too much time doing Google searches like how many cervical vertebrae great blue heron, or Ardia Herodias, how many neck bones it has. It doesn't really matter, I guess.

But I can tell you that the sixth vertebra in the necks of herons is special. This bone, the sixth cervical vertebra, has a unique structure that allows the bird to retract its neck into that iconic S-shaped curve. It also allows the heron to strike out with blinding speed, like a snake to catch its prey. That's where the bill comes in. The bill of the great blue heron is spear-shaped,

straight and pointy, with a length between five and six inches or about 14 centimeters. And like the tip of a spear, the heron's bill is flattened from side to side. Or in fancy terms, we say laterally compressed. This structure makes the bill strong and beautifully well adapted for piercing the water at high speed. I should mention that the Great Blue Heron has bright yellow eyes, and it has binocular vision

when it looks forward down the length of the bill and when it looks directly below. If you had this ability, you could face forward holding your head as you would if you were looking at the horizon, but in that same position you could roll your eyes down to look at your feet. You'd have enough depth perception to tie your shoes or try to solve a Rubik's Q. At the other end of the Great Blue Heron's body, the tail feathers are relatively short. But the wings are long and broad, spanning about six feet, or 1.8 meters. The bird flaps its wings slowly and deeply in flight. Here's what retro documentary man has to say about that.

The slow, graceful flight of the Great Blue Heron makes it one of our most spectacular birds. For more information on the Great Blue Heron, why not call it? Contact the Canadian Wildlife Service in Ottawa, K-1A-O-H-3. Yeah, why not contact the Canadian Wildlife Service in Ottawa? Why not? I'll tell you why not, because the Canadian Wildlife Service is probably understaffed and has more important things to do than respond to silly letters from people like me and you. Besides, if you need more information on the heron, just keep listening to this podcast episode.

By the time we're done here today, I'm sure I will have answered every question about the great blue heron that you could possibly conceive of. Anywho, those long legs allow the great blue heron to wade around in relatively deep water as it looks for aquatic prey. The heron's feet are strong, with three long toes facing forward and one facing backward. There's hardly any webbing between the toes, but great blue herons do on occasion swim by paddling around in water when it's too deep to stand in. The claw on the middle toe has an interesting feature. It has little notches along the side, sort of like the teeth of a plastic comb. This is called a pectinate claw, P-E-C-T-I-N-A-T-E. The word pectinate

comes from Latin and means resembling a comb. It shows up in other places in biology. For example, some insects, like certain moths and beetles, have pectinate antennae. Pectinate claws are rare in the avian world. Birds and only a few families have them, including herons, owls, and night jars. So what's the purpose of a pectinate claw? Well, just like your mom once used a comb to get the lice out of your filthy hair when you were a parasite-infested child, these birds apparently use their pectinate claws to comb parasites out of their feathers. And also to just tidy up their feathers in general, to prine. Speaking of feathers, it's time to have a look at the plumage of the great blue heron. In my opinion, naming this species the great blue heron was a bit of a stretch.

sure the gray parts of its plumage can look sort of bluish in the right light sort of but there's this very similar looking species the gray heron over in eurasia and africa so maybe someone wanted to make our north american bird seem special by calling it blue i don't know anyway it's perhaps more accurate to say this heron has a slaty gray coloration overall with some bold accents of white and black There are some rusty or buff-colored bits, too, like the feathers on the femoral area of the upper leg. And along the leading edge of the wing are some small patches of rusty pink feathers. Some might say they're a chestnut color. To me, these feather patches look sort of like wounds from a distance, like the bird got in a bar fight and were seeing some raw, damaged flesh on its wings. In the breeding season, great blue herons look a bit more flat.

lashy. They grow some lovely ornamental feathers on their heads, back, and breast. These feathers are long and thin, sort of hair-like. The ornamental feathers on the head, called occipital plumes, are black. Black patches of feathers on the sides of the head come together on the back of the neck. The eight to nine inch long plumes extend out from there, and that's about 22 centimeters years long. A great blue heron can raise or lower its head feathers using muscles in the skin. This is useful for communication. For example, the heron might erect those black occipital plumes when it wants other birds to know that it's feeling feisty and aggressive. Like other herons, the GBAH has some special feathers on its breast. Beneath the outer layer of contour feathers

are patches of powder-down. Powder-down feathers never stop growing and they never fall out during a molt. Their tips disintegrate into a fine dust made of keratin. The Great Blue Heron collects this dust, this powder, using that pectinate claw. Then it combs the stuff into the rest of its feathers. Powder-down helps to clean off fish blood and fish slime

and other gross things that can muck up the feathers. And Powderdown adds some waterproofing to the feathers as well. Besides having those ornamental plumes, our herons are more colorful during the breeding season because of what's going on with their bills and bear skin. The bill turns bright yellow, orange, or red, depending on which great blue heron population you're looking at. Here in the Pacific Northwest, for example, the bill tends to be yellow. But in Florida, it's more orange or red.

The area in front of the eye, what ornithologists call the lore, L-O-R-E, is bare skin on the great blue heron. This skin becomes blue or greenish in the breeding season. Again, the color varies by population. The legs, too, change color. In some regions, they're reddish. In others, they're more yellow. Male and female great blue herons look pretty much identical. Males tend to be a wee bit larger, but there's really,

really not much sexual dimorphism in this species. All right, what do great blue herons sound like? The vocal sounds of these herons are guttural and harsh, and mostly low-pitched. Here's a great blue heron in Sonora, Mexico, calling in flight. This next bird is also flying. It was recorded in the U.S. in Washington State. These are such wonderful primeval sounds. Some other types of great blue heron vocalizations are even more growly and dinosauric.

Perhaps not surprising for a large bird that many people compare to a dinosaur. But now I'm wondering, and maybe you are too, is dinosauric even a word? Did I just make that up? Let's do a little Google search. Okay, here we go. It is an actual word. Dinosauric means of, like, or relating to dinosaurs. Cool.

We all learned a new word today. Now let's go out and casually drop it into everyday conversations, confusing and annoying our friends by saying things like, hmm, this cookie tastes dinosauric. Or, I was going to take it. my dog for a walk today, but now I'm feeling kind of dinosauric, so I don't know. Or, is everybody ready to have the most dinosauric night of their lives? Woo! Woo! The Great Blue Heron is in the biological family, our deity. This group contains all the

herons, eagrots, and bitter. of the world. The root word there, Ardia, is also the genus of our beast, right? Ardia comes from Latin and means, and you're not going to believe me when I tell you, it means heron. Crazy, I know. And the specific epithet, the second part of the scientific name, Herodius also means heron. But this time, in Greek! There are 11 other species in the genus Ardia. The Greek, Great Blue heron's closest relatives are the cocoae heron, Ardia cocoae, and the gray heron, Ardia cineria, which I mentioned earlier. These three closely related species are similar in appearance and behavior.

They likely play similar ecological roles and are widespread in their respective parts of the world. As I mentioned, the gray heron lives in Eurasia and Africa. The cocoaee heron lives across most of South America. In fact, together, these three heron species form what biologists call a super species. But of course, you have to say it like, super species! Is this like the anime cartoon Voltron? Where a handful of smaller robots combined to become one enormous super robot? Maybe the Great Blue, Gray, and Cocoa,

herons join forces by merging their bodies into a gigantic super species that flies around, fighting crimes and stuff. I wish that were true, but no. In reality, a super species is a group of species, they could be birds, other animals, plants, whatever, that until pretty recently were just isolated populations of a single widespread species. The Great Blue, Gray, and Cocoa herons all share a recent common ancestor. a single heron species that made its way to various parts of the world. After some geographic isolation, mixed with a dash of genetic mutation over thousands of years, maybe even a couple million years,

the result was that one species split into three very similar but distinct heron species. All right, back to focusing on just the GBAH. Great Blue Herons across North America, Central America, and the Caribbean. aren't just one big, homogenous mishmash of identical birds. No, no, no. Because remember those regional color differences I was talking about earlier? There are also some consistent size differences among Great Blue Heron populations from one region to another. Ornithologists have been trying to sort out all this intraspecific variation, the variation within the species, for a long time. And this brings us to the idea of

subspecies in the Great Blue Heron. Just as a super-species is made up of several species, a single species is often composed of several subspecies. You with me there? Some ornithologists back in the day identified ten subspecies of the Great Blue Heron. But other ornithologists came along and said, No way, that's insane, man. Get out of here with your ten subspecies.

There are only like seven tops. More recently, a study published in 2004 by Robert Dickerman came to the conclusion that there are just four subspecies of Great Blue Heron in North America. Dr. Dickerman used museum specimens of herons and based his conclusions on body part dimensions and plumage differences. Briefly, I'll tell you about these subspecies. The subspecies, Ardia Herodius Fanonai, is found in. in the Pacific Northwest, from Alaska to the coast of Washington State.

The Ardia Herodius Herodius subspecies lives in central and eastern North America, as well as Central America and the northern edge of South America. Ardia Herodias Ward Eye is the subspecies you're most likely to run afoul of in southwestern Canada and in the western U.S., but inland, not at the coast. The fourth subspecies in North America is Ardia Herodius Occidentalis. That one is found in southern Florida and through the Caribbean. There's actually a fifth subspecies that isn't in North America at all. Ardia Herodias Cognada is found only in the Galapagos Islands of Ecuador.

But let's go back to that Occidentalis subspecies, the one in Florida and the Caribbean. You know how in the Lord of the Rings there was the wizard Gandalf the Grey? He was an old man wrapped in a cloak and stuff, sort of like a great blue heron standing at the edge of a wetland. But then in the story, and hey, spoiler alert, Gandalf falls into a hole and dies. But then he comes back in the next book as Gandalf the White. He's more powerful than ever. Remember that? Well, Ardia Herodius Occidental. The subspecies chilling in the tropical sunshine down there is all white. Seriously, its feathers are all white.

People call it the Great White Heron. It's as though the Great Blue Heron, which is actually gray, like Gandalf Version 1.0, fell into a hole and then got reincarnated as the Great White Heron. It was sent back to continue the fight against evil. For about 140 years, until 1970, the Great White Heron was considered a full-blown species, Ardea oxidantalus. But for as long as I've been alive,

it's been treated as only a sub-species of the Great Blue Heron. Some recent research, however, has ornithologists debating whether or not to restore the Great White Heron to its former glory as a species. A 2019 study on these birds, published in the journal The Ock, involved several types of data, including genetic data from heron DNA.

Great white herons, G-W-Hs, do show some genetic distinctiveness when compared to their G-B-H cousins. At the same time, there's evidence that the two color types interbreed, at least occasionally. There are several bits of supporting evidence used by scientists who argue that the Great White Heron should be kicked up a notch in terms of taxonomy to the status of species. That evidence includes, one, the consistent and dramatic color difference between these heron populations, a difference that's plain as day to anyone. Two, the moderate level of genetic difference between the populations. Three, the fact that Great Blues generally prefer to mate with other Great Blues. Likewise, the Great Whites tend to mate only with their own kind.

And four, birds in the two populations use different habitats. Great Blues lurk around in fresh and brackish water on the mainland, whereas Great Whites live in shallow saltwater habitats, mostly around islands. And I just realize it sounds like I'm talking about sharks. Calling these birds Great Whites makes them sound kind of scary. Like what if you were watching this documentary? Bloodthirsty and cunning, the Great White Hes. Heron lives in shallow coastal waters around islands. It prowls the knee-deep surf in search of its favorite prey, unwary children and Labrador retrievers frolicking in the waves.

Anyway, I should point out that some avian authorities, like BirdLife International, have already accepted the promotion of the Great White Heron to full species status. It'll be interesting to see if the American Ornithological Society will do the same at some point. So far, though, the answer is no. A proposal to make the Great White Heron a species was rejected by the classification committee back in 2020. Now let's talk a bit more about the habitats of the Great Blue Heron. This species is incredibly adaptable. That's probably why it has such a vast range across North America. We find these birds in all sorts of places where there's

some water nearby. Wetlands, lakes, flooded meadows, shallow coastal waters, mangrove swamps, riverbanks, and beaches. The Great Blue Heron isn't too shy about using habitats made by humans either, like cultivated fields, artificial ponds and lakes, city parks, etc. Any of these habitats, natural or otherwise, can attract herons as long as there are some fish in the water. GBHs nest in colonies, and we'll talk more about that in a few minutes. But in terms of nesting habitat, herons choose sites that are within a few kilometers from where they feed, and they select sites that are safe from mammalian predators. The best nest locations are high up in trees that are surrounded by water,

in relatively inaccessible places like swamps or on islands. Breeding habitat for our herons has, in some regions, become more available in recent decades. That's because the American beaver has made a comeback across the continent. Beavers build their dams, which cause ponds to form. Tall trees killed by the rising water behind a beaver dam can make great nest sites. When the habitat is good, some great blue herons will hang around their nesting colony pretty much all year. And that brings us to the question of migration.

Is this species migratory? Yes and no. It depends on the population. For example, great blue herons in the Pacific Northwest, the Fanonai subspecies, are non-migratory. They stick around all year. The same is true for the Great White Heron and the herons on the Galapagos Islands. Those guys are resident birds in their respective regions. But Great Blues in the rest of North America show some migratory behavior.

Most leave the northerly latitudes to find somewhere warm to spend the winter. Some individuals fly enormous distances, from Canada, for example, all the way down to the Caribbean or Central America. An individual heron that doesn't want to deal with the perils of long-distance migration might stay all winter long in the north. That strategy has its own challenges, of course. Herons spending the winter in the north need access to ice-free water so they can still catch fish and other aquatic prey. But in harsh winter weather, when all the water is covered in ice, a heron might be able to survive only by switching to eating small mammals. Great blue herons are such a familiar sight across North America.

You might assume that the species is doing just fine, and there's no need to worry about its conservation. And that's mostly true. The GBAH is doing okay these days. Its overall population seems to be stable and slowly increasing, with an estimated size between 500,000, and 5 million adult birds. A little over 100 years ago, however, things were very different. Great Blue herons were being hunted for their feathers, meat, and eggs.

Thankfully, the Migratory Bird Treaty Act of 1918 helped to put an end to the wholesale slaughter of herons and many other birds. The biggest threats to great blue herons today are habitat destruction, disturbance from human activities, and pollution in fresh and saltwater habitats. Many of the wetland habitats that herons need for nesting and feeding have been drained or paved over in North America. The fact that despite all this habitat loss, the Great Blue Heron has a large and increasing population is probably because of how adaptable this species is. And we can also thank the massive efforts of conservation organizations in protecting the wetlands we still have. Not all Great Blue Heron populations are doing equally well, however.

The Great White Heron, the subspecies that might be a species again someday, has been going downhill in southern Florida. One hypothesis for why the Great White Heron has declined is that its shallow water seagrass habitats have become degraded. Habitatation from boats and other human factors reduces the number of fish available for the herons to eat. That could be why the herons have switched to eating unwary children. These birds actually have a large nature preserve named after them. A collection of small islands in the Florida Keys are protected within the boundaries of the Great White Heron National Wildlife Refuge, which was established in 1938.

The Great Blue Heron is a carnivore, through and through. This bird will eat just about any creature it can snatch and swallow. A wide variety of fish, from small to fairly large, are on the menu. But a G.B.H will happily kill and hold. hork down large insects, crustaceans, frogs, lizards, snakes, small birds, and small mammals. The diet of herons in a particular habitat probably depends mostly on which small critters happen to be abundant there. For example, in relatively dry upland habitats like meadows and agricultural fields, a great blue heron will stalk prey like mice, voles, gophers, and snakes.

Or there was the Great Blue Heron that used to visit my old neighborhood in Portland, Oregon, right in the middle of the city. More than once, I watched this huge heron land on my neighbor's roof, then swoop down to their fish pond to snatch up a couple big goldfish out of the water. What a cheeky bird! It knew what it wanted and just went for it. Great Blue herons can swallow some surprisingly large prey. A heron weighing only about five pounds might swallow.

a fish, gold or otherwise, that weighs one pound. These herons will even eat things like baby alligators, rabbits, stingrays, or other wetland birds like ducklings or rails. But sometimes the heron's yellow eyes are too big for its stomach. Well, too big for its gullet is what I should say, because these birds can choke to death if they try to swallow a prey animal that's too large. The heron's long, spear-shaped bill combined with that S-curved lightning-quick neck make for a highly effective apparatus for catching prey. The Great Blue Heron is an ambush predator. It's the exemplar of patience as it stands stock-still, waiting for a fish or other animal to come within striking distance. In a contest of who can stand still the longest and keep their cool while

being harassed by annoying tourists, I might actually bet on the great blue heron to win against one of those royal guards standing outside Buckingham Palace. Whether standing and waiting or wading stealthily through the water, the heron looks for its next meal. When the moment comes for it to strike, the bird launches its head forward at high speed. The streamlined bill and head easily cut through the water. It's uncommon for the bill to actually stab or pierce the prey animal. Instead, the bill opens up at just one-thirtieth of a second before impact. So it works more like pincers or forceps to grab the victim. Great Blue herons forage both in the day and at night. Like other members of its family, the light-sensitive

cells in the eye of a G.B.H. are mostly rods. Rod cells, you might remember, are the ones that work best for night vision. Cone cells, on the other hand, are the ones that are great for color vision. To small animals, the Great Blue Heron really is the terror of the marsh, the Tyrannosaurus Rex of the wetlands. And like T-Rex, this bird is a top predator, at least in some ecosystems. For example, there was this 2015 study on Great Blue Herons living on the coast in British Columbia, Canada. So that's the Fanonai subspecies, right? These birds forage for bottom-dwelling fish in a shallow saltwater habitat dominated by eel grass. In this study, the researchers set up an experiment where they kept great blue herons from having access to some patches of eelgrass habitat.

There were 12 patches. Six of them were experimental, and six were the controls, each measured four by four meters. Herons were kept out of the experimental patches by a frame of PVC pipe criss-crossed with pink string because everybody knows that great blue herons can't stand the sight of pink string. In the control patches, there was none of that god-awful pink string, and so the herons could come and go as they pleased in those patches. After running this experiment for several months, the researchers found evidence that herons have a big effect on the eel grass

ecosystem. In the patches where herons had been kept out, there were significantly more fish at the end of the experiment, and significantly fewer invertebrates. This all has to do with the local food chain, or more realistically, the local food web. Great Blue herons are the top predators. Under natural conditions, they eat the fish and the fish eat the small invertebrates. If there are no herons to eat the fish, the fish population is higher than normal, and all those fish eat more invertebrates. The Circle of Life, yada, yada. An adult great blue heron will often defend a feeding territory from other herons. Trespassers are threatened or chased off or attacked. One dramatic, some might say dinosauric threat display made by a territorial heron is the

upright and spread wing display. The territory holding bird moves toward an intruder with its wings spread wide and head held high on its outstretched neck. It's basically the heron equivalent of come at me, bro, you want some of this? Come at me! Territoriality in these birds explains why, when you're boating along a river or in an estuary, you might see heron after heron standing on the shore. They're spaced evenly apart, more or less, because of their aggressive territoriality. One study in Oregon found that Great Blue Heron territories were, on average, 129 meters apart on the shore of a freshwater marsh. Another interesting factoid about Great Blue Heron Territoriality comes from a paper published in 1980 in the journal The Ock. What was the paper's title? Social Differences

differences in defecation behavior of great blue herons. And this is real, I'm not making this up. This study found that when a heron feels the need to do its business, a bird in its own territory will leave its foraging spot in the water. It will walk or fly a short distance away, defecate, then return to the water. It's careful not to poop where it eats, as the old saying goes. But the study reported that non-territorial herons behave differently. While waiting around looking for fish, a non-territorial heron is likely to just drop it like it's hot right there in the water. It just poops right there. The bird is probably just passing through.

It's like, this isn't my territory, so who cares? Let somebody else clean it up. This behavior kind of reminds me how people treat hotel rooms versus how they treat their own home. Adult great blue herons might have to fear each other sometimes, but they don't have too many other animals to be afraid of. They themselves don't fall victim to other animals very often. But bald eagles do sometimes kill and eat great blue herons. Eggs and young herons in the nest, however, are much more vulnerable to predators.

They can get eaten by eagles, owls, ravens, crows, raccoons, red-tailed hawks, and so on. But heron chicks sitting in the nest aren't completely helpless. When a raccoon or other mammalian predator tries shimmying up the tree trunk toward the nest, it might be in for a very nasty surprise. Because great blue heron chicks will sometimes lean over the edge of their nest and vomit all over the invader coming up from below. I don't know if I was a raccoon climbing up that tree thinking, oh yeah, I'm going to eat me a greasy little baby heron. Then I get blasted in the face with hot half-digested fish guts? I'd be like, nope, nope, never mind.

I'd probably fall out of the tree and break a few of my little raccoon bones in the process. Great Blue Herons form monogamous pears each breeding season. The pair works hard to raise a family over the spring and summer. But then they go their separate ways. Most of the time a great blue heron will find a new mate each breeding season. The species nests in colonies, as I mentioned. Dozens or hundreds of nests are built close together in trees. They're often 100 feet or more off the ground.

But in some habitats where there aren't so many tall trees, like in mangrove forests, the nests are much lower. This breeding colony has a special name. It's called a heronery. That's H-E-R-O-N-R-N-R-Y. A heron-ry can be a noisy place when there are both adults and chicks all making their throaty calls. Males are usually the first to arrive at the heronry in late winter or early spring. They move into old nests or they start working on new ones.

When the females show up, it's time for some courtship behavior. Great Blue Herons have elaborate courtship displays. The many displays have names, including stretch display, snap display, wing preen, circle flight, twig shake, fluffed neck, bill clappering, etc. As they build their nest together, the male and female reinforce their bond by displaying for each other. For example, there's a ritualized sequence of displays called the Stick Transfer. A male returns to the nest with a stick. The female in the nest performs a stretch display, where she extends her neck to the sky, pointing her bill upward.

She then takes the stick from the male. While she places the stick in the nest, the male makes a bill clapper display in her general direction. Clappering is where a heron clicks its bill rapidly. The nest is basically a pile of sticks. It's in the platform category of nest. which I talked about in the nest episode, Episode 49. Brand spanking new heron nests are only about 20 inches in diameter, which is about 50 centimeters.

But nests that have been maintained and added to for years and years can be much bigger, up to four feet across, or 1.2 meters. The female great blue heron lays two to six pale blue eggs per clutch. Both parents take turns incubating the eggs. eggs. Dad takes the day shift sitting on the eggs and mom incubates them at night. There's this crazy video from a nest cam where a great horned owl repeatedly attacks a nesting heron one night. I'll put a link to the video in the show notes. To me, this video is a reminder of how challenging life can be for a bird, how hard it is to stay safe and stay alive, and how hard it is to raise even one chick

successfully. The pair of adult herons incubate their eggs for about a month. Once the chicks hatch, the parrins take turns feeding them. The chicks are born squawking and covered in gray down feathers. Siblicide is not uncommon among the heron chicks in a nest. Especially when food is scarce, a larger, stronger chick might kill one or more of its smaller siblings by pushing them out of the nest. Other bird species do this too. Siblicide is not unique to herons. Yes, it's sad and seems cruel, but it's a behavioral adaptation that makes it more likely

that at least one chick will live to adulthood, because sometimes there just isn't enough food for every chick to survive. Seven or eight weeks after they hatch, any young herons that didn't get killed by their siblings are about ready to fledge. They make their first flights. The young become independent a few weeks later.

At first, they aren't all that great at catching fish or frogs or gophers, but they learn quickly. Life is hard for juvenile great blue herons. Some studies have estimated that almost 70% of these birds don't survive their first winter. But the ones that do survive their first couple winters have much better chances of living a reasonably long life. And how long might that be? The oldest wild Great Blue Heron was 24. The Great Blue Heron is actually the official bird of my home city, Portland, Oregon.

The mayor and city council made the proclamation back in 1986. We love our GBHs here in Portland. We name beers after them. We paint enormous murals of them. We let them eat all the goldfish out of our backyard ponds, apparently. Heron imagery is everywhere in Portland, and I love it. I'll leave you with a poem by William Stafford. He wrote it specifically about the herons of Portland.

The poem is called Spirit of Place. Out of their loneliness for each other, two reeds, or maybe two shadows, lurch forward and becomes suddenly a life lifted from dawn or the rain. It is the wilderness come back again, a lagoon within our city reflected in its eye. We live by faith in such presences. It is a test for us, that thin but real, undulating figure that promises. If you keep faith, I will exist at the edge where your vision joins feet that go down in the mud, where the truth is. Thank you, my friend, for diving into the world of Ardia Herodias with me today. If this bird was already familiar to you, I hoped you learned at least a few new things about it.

Or if the Great Blue Heron isn't familiar to you, like if you live in Australia or something, well, you just learned a whole bunch of new facts. Lucky day! Some of my listeners recently stepped up from being rando fans to being full-fellied. fledged patrons of the Science of Birds. These are my newest supporters on Patreon. Andrea Devlin, Dustin Weidner, Ray Lynn Jensen, John Ensign, and Joanne.

Thank you all so much for offering your support. It's much appreciated. And thanks to all my other loyal patrons out there. You're making this whole thing possible. Becoming a patron is easy and fun. Just go check out my Patreon page at patreon.com slash Science of Birds. You can send me an email if you have something you'd like to share,

your thoughts about the podcast, perhaps. Or maybe you somehow thought of a question about Great Blue Herons that I didn't answer today. I'm pretty sure I covered absolutely everything, but just in case, my email address is Ivan at Science of Birds.com. As always, you can check out the show notes for this episode, which is number 70, on the Science of Birds website, scienceofbirds.com. This is Ivan Philipson, wishing you nothing but good times ahead. Peace.