The Science of Birds - Sage Grouse

Episode Date: September 2, 2025

👕 Bird Merch —  Get yourself some bird shirts!~~~This is Episode 122. Host Ivan Phillipsen takes listeners into the vast sagebrush steppe of western North America and introduces the remarkable birds that call it home—the sage grouse. These birds are icons of the American West, tightly bound to a rugged ecosystem that covers nearly a third of the lower 48 states.Ivan explores how sage grouse have evolved to thrive on a diet of sagebrush—plants laced with bitter, toxic chemicals that most animals avoid. From their unusual digestive adaptations to their elaborate courtship displays, these birds reveal fascinating strategies for survival in a tough landscape.Listeners will learn about the two species of sage grouse, their distinctive appearances and behaviors, and the conservation challenges they face today.Links of InterestBody-popping sage grouse - Nature's Greatest Dancers - BBC [VIDEO]Link to this episode on the Science of Birds websiteSupport the show

There's a special ecosystem in Western North America that spreads across the wide plateaus and basins between the Cascades and Sierra Nevada ranges and the Rocky Mountains further east. We're talking about the Sagebrush Step ecosystem, S-T-E-P-P-E. It covers almost one-third of the lower 48 states in the U.S. To many people, sagebrush landscapes embody the feel of the west, open skies, rolling hills and plains, few trees, and the silvery gray expanse of shrubs stretching to a distant horizon. The climate here is hot and dry in the summer, bitterly cold, and windy in the winter. It's not an easy place to live.

And yet, there's a surprising amount of biodiversity in the summer, the sagebrush step. The vegetation is a mix of wildflowers, grasses, and shrubs. And not surprisingly, the dominant shrubs are the sagebrushes. These plants belong to the genus Artemisia, A-R-T-E-M-I-S-I-A. And they're in the plant family, Asteraceae, which you might know as the sunflower or Aster family. There are about 500 species in the genus Artemisia worldwide, and And these also include the plants we call wormwoods. Western North America is home to dozens of Artemisius species. One of the distinguishing features of these plants is the chemical compounds in their leaves that give them a strong aroma and a bitter taste.

These chemicals are defenses that the plant makes to repel hungry herbivores, who would otherwise very much like to munch on the leaves. So these chemicals are essentially poisonous. And yet, in the human world, we've used some Artemisia species in things we drink or eat. Artemisia absinthinem provides an essential ingredient in the alcoholic drink Absinthe. Still poison, maybe, but a tasty, tasty poison, I guess. Another example is the spice tarragon, which is frequently used in French cuisine. Or so I've heard. I don't know what Tarragon tastes like, because I guess I'm not aristocratic enough to dine upon French cuisine, but I'm sure it's good.

Anyway, Tarragon comes from the plant Artemisia Dracunculus. Dracaris. No, no, Calisi, I said Artemisia, Dracunculus, not Dracaris. Not the thing you say to roast your enemies with dragon fire. Now, back to the sagebrush step. Probably the most famous species is Artemisia Tridentata, better known as Big Sagebrush. This is one of the most iconic plants of Western North America. It dominates vast areas of the Great Basin, Columbia Plateau, and high deserts west of the Rocky Mountains.

It has small gray-green leaves with sort of a three-pointed tip. That's why it's Artemisia Tridentata. and the leaves are coated in fine hairs that help to reduce water loss. When you crush the leaves in your fingers, they release a really strong and sort of resinous, unmistakable aroma. It's a smell that anyone who has froliced in the sagebrush country should recognize. As I said, the chemicals in the leaves of Artemisia are basically poison, right? Or they're at least nauseating and unappetizing to most would-be plant eaters.

Now, if you're thinking, why is this guy talking about plants and when the heck is he going to start talking about birds? Well, my friend, the time has come. Because some bird species are specially adapted to a rugged life on the sagebrush step, and they have evolved the ability to eat Artemisia leaves. Yes, I'm talking about sage grouse. It's right there in the name. these birds are intimately linked with sagebrush habitat. And their highly specialized diet is mostly sagebrush plants, Artemisia. Not only do sage grouse eat the plants,

they positively thrive on them. If you can evolve the superpower of being able to live on a diet of what is basically poison salad, you have a major advantage. You have unlocked access to an ecosystem and a food source that's pretty much all your own. You have very little competition. But as we shall see in today's episode,

this superpower, this specialization comes at a price. 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 122. It's all about sage grouse, birds belonging to the genus Centro Circus Centro Circus. There are just two species. The greater sage grouse, Centro circus

Europhazianus, and the Gunnison Sagegrouse, Centro Circus Minimus. I should point out that the common name of the latter species is not gunnissons. It's not gunnissons. It's not possessive. And it's definitely not son of a gun, sage grouse. Although that would be fantastic. But no, it's just the gunnison sage grouse. And if you'll permit me a little digression here about grammar, you know, because these are the kinds of things that keep me up at night, rocking back and forth in my pajamas, muttering to myself as I scroll through online dictionaries on my phone. I wanted to know, grammatically, how do we refer to these birds in the plural? My understanding, after those sleepless nights of research, is that the best thing to do is to use

grouse for both the singular and plural. Now, maybe that's common knowledge. Maybe you want to say, well, duh, Ivan, I could have told you that. Ah, yes, but what about when you're referring to not just multiple individuals, but to multiple species. Because I learned back in the day in the hallowed halls of academia that with fish, you would say fishes when you're talking about different kinds, different species. Logic would tell us to do the same with grouse. Here, for example, is a rowdy bunch of individual greater sage grouse.

A rowdy bunch of grouse. But if you've got a motley crew of, let's say, a sessie. stage grouse, a sooty grouse, a ruffed grouse, and a Siberian grouse. Got to watch out for that guy. Well, I'd say you're looking at some grouses in that case. Or logic might tell us to use grouse for the singular and grice for the plural, right? Because mouse, mice? But the English language is anything but logical.

What works for fish and mice doesn't necessarily work for grouse. The dictionaries and other resources tell us that saying grouse's for multiple species isn't so much a thing these days. So I'll just use grouse for both the singular and plural. Back to the main storyline here. So we've got the two species, right? The more famous and widely distributed one is the greater sage grouse. These guys have been featured in many nature documentaries over the years,

primarily because of their crazy courtship displays and breeding behaviors. So we'll talk about all of that in some detail today. Fewer people have probably heard of the Gunnison Sagegrouse. This bird was identified by ornithologists as a distinct species fairly recently in the year 2000. Before that, what we now know are Gunnison Sagegrouse populations were just lumped in with the greater sage grouse. the son of a gun the i'm sorry the gunnison sage grouse is genetically distinct from the greater sagecrouse the gunnison sage grouse looks and sounds different and it occupies a much smaller geographic range primarily in southwestern colorado and southeastern utah the gunnison sage grouse gets its common name from the gunnison basin in gunnison county colorado that's the region where the species was first recognized as being a separate species. Both species are icons of the American West, particularly of

sagebrush country. They have a lot of fans among birders and nature lovers. And yet these birds face many threats, as we shall discuss later. Let's go ahead and get to know these birds, starting with their appearances and sounds. The two sage grouse species are very similar to the untrained eye, so it's not surprising that they used to be lumped together as a single species. By default, I'll focus on the greater sage grouse today, but I'll point out how the Gunnison sage grouse differs along the way. These birds are vaguely chicken-like in their body shape and overall vibe,

and they're reasonably close relatives of chickens since they're in the same family. Sage grouse are large, chunky-looking birds with relatively small heads and fairly long tails. The greater sage grouse is actually the largest grouse species in North America. That's compared to birds like the sharp-tailed grouse, greater prairie chicken, and dusky grouse, all of which are smaller. But the gunnison sage grouse is distinctly smaller than the great. greater sage grouse, being only about two-thirds or even one-third the size. Males of both sage grouse species are significantly larger than their female counterparts. For the greater sage grouse, males weigh between four and seven pounds, which is 1.8 to 3.2

kilograms. Males in this species measure 26 to 30 inches long, or 66 to 76 centimeters. Females, on the other hand, are more like 2 to 4 pounds, or 0.9 to 1.8 kilograms, and 19 to 23 inches long, which is 48 to 58 centimeters. This sexual dimorphism, the size difference between males and females, is most obvious in early spring during the breeding season. By that time, the males have been bulking up for months, so they look all like swole, relatively supersized. Now let's look at the plumage patterns and colors on these birds. Again, the two species look superficially quite similar. Their feathers are mottled brown and gray with some white streaks and white feather tips. This provides excellent camouflage among the sagebrush.

Females maintain this camouflaged look year-round. Both sexes have a conspicuous black patch on their belly, and their legs are feathered down to their toes. males during the breeding season have the iconic appearance you might already have a mental image for. There's a vague similarity between displaying male sage grouse and male wild turkeys. Turkeys, too, are in the same family as sage grouse and chickens. Here's what a male greater sage grouse looks like when he's displaying, showing off for the ladies. He has a black throat and a bright yellow fleshy comb or patch of bare skin above each eye.

There are wiry black filipulums sticking out of the back of the neck. Remember that filipulums are hair-like feathers that have no or very few barbs. The male sage grouse has a fluffy white ruff of feathers around his neck and upper chest. During the male's elaborate courtship display, the white ruff surround. two bulbous yellow air sacks on the bird's chest that expand like round balloons. When the sacks are inflated, they look sort of like a pair of... a pair of sunny-side-up eggs. Seriously, each is a circle of yellow surrounded by a mass of fluffy white.

And okay, who are we kidding? The air sacks also look sort of like a pair of breasts. Like maybe don't let your boss catch you looking at pictures of sage grouse on your computer. NSFW, not safe for work. Just kidding. The resemblance is just pure coincidence, though. These air sacs are in no way related to the mammary glands of mammals. The technical name for these air sacs is cervical apteria.

Servical because of where they're located on the bird's body. Servicle refers to the neck area. And remember that aptaria means no feathers. It's a patch of bare skin. on a bird that, for one reason or another, has no feathers or relatively sparse feathers. Anyway, the male sage grouse has a long pointed tail. He spreads it out during his display into a fan, a sort of starburst shape of spiky feathers. And there's an array of shorter feathers underneath the spiky ones, and those are chocolate brown with white tips. To me, the fanned out

tail feathers look like the spiky crown on the Statue of Liberty, or a lot like the iron throne in Game of Thrones, you know, the one made out of a bunch of melted swords, and hey, there you go, that's two Game of Thrones references in one episode. But I promise, I'll stop now. So how does the Gunnison Sagegrouse look different from its larger cousin? Well, Gunnison Sagegrouse are generally a darker shade of brown overall. And a key distinguishing feature is their much longer and thicker ornamental plumes, those fillipulums that stick out from the back of the neck. On the Gunnison Sage Grouse, these feathers create a sort of black ponytail look when the bird displays. Another crucial distinction is that the tail feathers on a Gunnison Sage Grouse have

these thick brown bars alternating with prominent white or yellow white bars. This distinct barring is much more in your face than what you see on the greater sage grouse. Okay, now let's talk about the sounds these birds make. First, I'm going to just play you a recording made in Montana of a few dozen greater sage grouse. These are males making courtship displays. Just listen to the variety of sounds you hear in this recording. And try to ignore the prairie dogs making alarm calls in the background. Okay, you know, Okay, you probably heard some sounds in there that were like a water drop, like a plop sound. And there were

some tonal sounds too, more like soft whistles and coos. Here's what's going on. We'll talk more about the courtship displays later, but let me focus on the sounds for now. For these greater sage grouse, the display begins with the male taking deep breaths, gulping and holding air in those air sacs, the cervical aptaria, which can expand to hold up to four liters of air. Yet another name for those yellow balloon-like structures is esophageal pouches. Anyway, the male swishes his wings against stiff white breast feathers, that rough, creating a distinctive sound. The wing swishes sound to me almost like the strident call of a bird, like a house sparrow or something. The wing swish is followed by a series of low, single-frequency cooing sounds.

But the real core of the acoustic display is that plop sound, also called air sac pops or snaps. The plop is a broadband sound that gets amplified by the inflated air sacs. These plops happen when the air sacs rapidly inflate, bounce, and deflate. Typically, the greater sage grouse produces two plops, with a frequency, modulated whistle uttered between the first and second plop. Now, while the coo notes tend to be the loudest in front of the bird, the whistle has a different and distinctive acoustic pattern. Interestingly, it's hard to hear it directly in front of the bird, but it's intense to the

sides and behind, meaning the male can stand at an angle, sort of diagonally, relative to a female, to deliver a high-intensity whistle blast. The sound of these displays can carry as far as two miles across the sagebrush step. That's three kilometers. A bunch of males making a racket like this is what attracts females from far and wide. All right, now let's listen one more time to that group of displaying males. Listen carefully to see if you can separate out the wing swishes, plops, coos, and whistles. There are some other birds singing in the background like Western metal larks.

But once again, I implore you to please, for the love of God, ignore any prairie dogs that you might hear in this recording. Sage grouse and all other grouse speech. Sage grouse and all other grouse species belong to the family, Phasianity. This is a widespread family with 185 species. And believe it or not, this is the first Science of Birds episode to focus on any bird in that family. Unless, of course, I'm forgetting something. In any case, I'll do an entire episode on the family Phasianity at some point.

For sure. Now, both species we're talking about today are in the same genus, right? Centro Circus, C-E-N-T-R-O-C-E-R-C-U-S. And just hearing that word, you might think it has something to do with a centrally located collection of large canvas tents, each of them crawling with clowns. But nope, Centro Circus comes from two Greek words, Kentron and Kirkos. Put them together, and they mean pointed tail. The greater sage grouse is Centro Circus Europhazianus.

Without looking it up, if I were to interpret that second word, the specific epithet, I would say it means pheasant-tailed. But that's way off, because apparently Europhasianus borrows its structure from Eurogallus, which is the specific epithet for a bird called the Western Capercaly. That's a big, beefy member of the pheasant family that lives in Europe and Asia. Eur-U-R-O in both of these names doesn't mean tail. It's not Greek in origin. It actually comes from the German word Auerhaan, and that refers to the Aurox, the ancient ancestor of domestic cattle.

So URO, URO, in the case of these birds, means bull. For our greater sage grouse then, the full scientific name translates as pointy-tailed bull-feasant, bull because it's large and robust. You know, strong-like bull. The two sage grouse species are, of course, each other's closest relative. But which other species in the pheasant family are most closely related to the sage grouse? A genetic study back in 2000, using mitochondrial DNA, found that sage grouse are closest to the North American prairie and forest grouse, in the genera tympanukus and dendragapis, respectively.

So we're talking the sharp-tailed grouse, the prairie chickens, the sooty grouse, and the dusky grouse. In terms of where you find sage grouse, both species are what we call obligate residence of the sagebrush step ecosystem. Obligate because they're found only in this ecosystem. And they're residents because they don't migrate. They hang out among the sagebrush shrubs all year long. This intimate association between birds and bushes is so strong that the distribution maps, the range maps of sagegrouse, closely match the map of sagebrush habitat across North America. Well, that was the historical situation anyway, before European colonization began.

The current ranges of the two species are fragmented and severely reduced compared to what they were a couple hundred years ago. The greater sage grouse has lost an estimated 44% of its original range. Its current distribution spans 11 U.S. states, including parts of Washington, Oregon, California, Nevada, Idaho, and Montana. There are also some populations in Canada, in southern Alberta and Saskatchewan. The Gunnison Sagegrouse has lost an estimated 90% of its original range. That species is now limited to just seven isolated areas in Colorado and a single small population in Utah. Let's talk a little more about habitat. We know that these birds are obligate residents of sagebrush ecosystems. They rely on various sagebrush species, and patches of those plants are often

interspersed with other habitats like riparian meadows, grasslands, and agricultural lands. But it's the sagebrushes that meet most of, or almost all of the needs grouse have, for food, cover, and nesting, raising chicks. As I mentioned earlier, there are dozens of sagebrush species in this ecosystem, many different members of the genus Artemisia. And some of them, like big sagebrush, have multiple subspecies. So sage grouse have their preferences for which types of sagebrush make good cover or nesting areas versus which of those are good to eat. They eat species like big sagebrush, low sagebrush, silver sagebrush, black sagebrush, fringed sagebrush, and mango pineapple sagebrush.

Mmm, mango pineapple. As delicious as that sounds, I have to admit that no such Artemisia species exists. Sorry. I was just checking to see if you were paying attention. And you know, thinking about wonderful flavor, and smells. I got to tell you, the scent of those toxic chemicals, the essential oils of sagebrush, that is one of my all-time favorite smells. I like to crush a pinch of the leaves in my fingers and breathe in those volatile compounds. It's all minty and refreshing. I can't get enough of it. And of course,

it evokes the feeling of being in a wide open landscape far from civilization. It's wonderful. And when I was in Mongolia recently, one of the pleasant surprises for me was that the steppe ecosystems there, those vast grasslands also have some Artemisia species. There are lots of these little tiny bushes. And the leaves on those Mongolian bushes too have that wonderful, distinct smell. I love sagebrush so much that I'm thinking about naming my first daughter, Artemisia. It's got a nice ring to it, right? Anyway, Habitat. The sagebrush step has very few trees, and my understanding is that sage grouse really don't like trees. It might not even be an exaggeration to say that sage grouse hate trees. Who knows?

The problem with trees is that, in some cases, they displace sagebrush. And that's unacceptable for the grouse. But maybe the real problem is that trees make great perches and lookout towers for avian predators. Hawks, falcons, and corvids eat sage grouse and their chicks. These predatory birds can sit in a tree to scan the shrubbery for any sage grouse. So our grouse tend to avoid trees like the plague. If there are even a few juniper trees in a patch of habitat, sage grouse are less likely to be found there. Although sage grouse don't really migrate, they do move around a bit, especially in winter. They need to find patches of sagebrush that aren't buried in snow. And if there's harsh winter weather, that might motivate grouse to move to greener pastures,

sometimes miles away. At least temporarily, because these birds exhibit strong sight fidelity to their breeding and nesting areas and to their winter ranges. In other words, they often return to the same areas year after year. Such sight fidelity is a good survival strategy, when the habitat remains more or less the same over long stretches of time. But it limits the bird's ability to adapt to any rapid habitat changes. Like, you know, all the changes made by us, people.

Sage Grouse have been around for at least 1.6 million years. We know this because the earliest fossil we have for one of these birds dates to around that time, 1.6 million years ago. It was found in a cave in Park County, Colorado. Other fossils of grouse dating to between 13,000 and 18,000 years ago reveal a widespread distribution for these birds. So we're talking about the late Pleistocene epoch, the last glacial period. Back then, these birds were found across a larger portion of North America,

at least as far south as New Mexico. But pollen records suggest that sagebrush habitat was, even in the Pleistocene patchily distributed. It was discontinuous. So sage grouse populations would have been fragmented at that time. And they've become more and more fragmented

ever since. The two species, the greater and Gunnison Sagegrouse, share a recent common ancestor. Research using genetic data gives us a rough estimate of about 1.24 million years ago for when that single ancestral species

split into the two lineages. Once the lineages became isolated from each other, maybe because of sagebrush habitat fragmentation, sexual selection may have taken over. Remember that I did an episode on the topic of sexual selection, episode 27? It's fascinating stuff. Well, if females in the two lineages differed even a little bit in their preferences for male display traits, that could, over 1.24 million years lead to the differences we see today between the Greater Sage Grouse

and the Gunnison Sage Grouse. Sexual selection based on female choice is probably why Gunnison males have those distinct features we talked about. The pronounced white barring on their tail feathers, the ponytail-like filipulums, and the differences in their courtship displays. Interestingly, scientists have suggested

that the Gunnison Sage Grouse is an example of an intermediate stage of speciation. It's already reproductively isolated from the greater sage grouse, yes, but at the level of DNA of the genes, the two species are

still diverging. There's one more interesting thing I want to mention about the genetics and evolution of these birds. There's an isolated population of grouse that lives on the California-Nevada border in the mountain basin surrounding Mono Lake.

This population might, might represent a third species, because it's genetically distinct from other greater sage grouse populations, showing unique mitochondrial DNA and significant differentiation in nuclear genes. This genetic difference is comparable to the level that separates the Gunnison sage grouse from the greater sage grouse. Additionally, this monobasin population appears to have been isolated for a long time by natural geographic barriers. And that might be why it has accumulated those genetic differences. However, scientists haven't formally reclassified this population as a new species. One argument against it being treated as a new species is it seems to lack any clear

differences in its physical appearance or its courtship displays, compared to the greater sage grouse, that is. As far as I know, there isn't any current scientific consensus or active move to elevate the monobasin population to the species level. But since it's a genetically distinct, isolated population, it's probably on its own evolutionary path. Maybe it will adapt and change in different ways from other sage grouse populations over time. This brings us to the conservation situation for some. sage grouse. It's a long, complex story, one that's probably worth an entire podcast episode itself.

But for today, I'll just try to keep it to the basic facts. Long story short, these birds are not doing great. Remember that before European humans crashed the party in North America, the range of greater sage grouse was almost two times as large as it is today. And the gunnison sage grouse used to have a range ten times larger. The International Union for the Conservation of Nature, the IUCN, places the greater sage grouse in the near-threatened category on their red list. The most recent estimate for the total population size of this species, the estimate from this year, is between 200,000 and 500,000. Now, maybe that sounds like a lot of birds, but not when you understand that the population of this

species has declined by 70 to 80% since the mid-20th century. And it's still declining. The Gunnison Sagegrouse is in the endangered category on the IUCN Red List. The most recent total population size estimate for that species is only about 4,000 birds. So the Gunnison Sagegrouse is one of the most endangered birds in North America. So what's going on? What's the problem here? Why have these lovely birds suffered such massive population declines? I'll give you one guess about what has been and continues to be the biggest threat to sage grouse. One guess. If you answered habitat destruction, you are correct.

That's almost always the answer, isn't it? For most of the last 200 years, many Americans have discounted sagebrush step as, being kind of worthless. So the habitat has been plowed over or burned at a massive scale, mostly to make room for animals like cows, sheep, and humans. Sagebrush has been replaced by crop land, grazing land, urban development, and energy development like oil, gas, wind, and solar. Another thing that destroys habitat is wildfire.

Now, fire is, of course, a natural part of this ecosystem. Historically, a patch of sagebrush might burn every 150 to 350 years or so, on average. Wildfires kill sagebrush shrubs, which can take 20 to 150 years to recover. But humans have introduced fast-growing invasive plants like cheatgrass that often fuel unnaturally large fires. So fires are now more frequent and more devastating than they ever were in the past. And then, of course, there's climate change. Climate change models for the American West predict higher temperatures, drier soils in summer, and more severe weather.

And none of that is good news for our grouse. Thankfully, there are conservation organizations and partnerships of various stakeholders that have been trying to protect the sage grouse and their habitat. But because there are multiple stakeholders, including wildlife advocates, ranchers, farmers, and energy developers, and the interests of these groups often conflict, sage grouse conservation has been complex and challenging. And as you can imagine, there is a lot of politics involved.

The Gunnison Sagegrouse is listed as a threatened species under the U.S. Endangered Species Act. So that means it has protection at the federal level. But the Greater Sage Grouse is actually not on the endangered species list. Proposals to list that species were withdrawn back in 2015. The story is, as I said, complicated, and it's messy. But since 2010, one of the biggest efforts to protect the Greater Sage Grouse has been the Sage Grouse Initiative, a partnership-based, science-driven, farm-bill-funded effort by the USDA's Natural Resources Conservation Service. The sage grouse initiative uses voluntary incentives to conserve western range lands, and since 2010, the initiative has conserved 9 million acres of habitat.

Meanwhile, there are ongoing legal battles related to listing the greater sage grouse as endangered under the Endangered Species Act. But these are multiple separate efforts rather than a single comprehensive campaign. It's time to look more closely at what and how these grouse eat. As we've been talking about, the two species are dietary specialists, adapted almost entirely to a diet of sagebrush leaves, minty, pungent, toxic to everybody else, Artemisia leaves. In winter, sagebrush leaves are pretty much their entire diet. But the diet shifts when the seasons turn. In summer and early fall, sagebrush is still important, but Forbes, those non-grassy herbaceous plants, and some invertebrates are added to the diet. Adult females,

especially, chow down on protein-rich forbs like dandelions, legumes, and Yarrow in the weeks before egg-laying. It's like they're loading up on prenatal vitamins. The toxic compounds in sagebrush leaves are called plant secondary metabolites. Plants make such chemicals to protect themselves from herbivores, to avoid being eaten. But then, in this case, evolution acting on behalf of the grouse was like, ha ha ha! I laugh in your face, sagebrush. You expend such precious energy to make secondary metabolites. But lo, I have gifted unto these birds the power to vanquish your many poisons. Your monoturpenes, sesquiturpine lactones, and phenolic compounds are no match for the ravenous hunger of the sage grouse. To these birds, your secondary metabolites are like sweet, sweet candy.

So yeah, sage grouse have digestive adaptations that let them tolerate these chemicals. Most importantly, they've got a specialized system in their liver using enzymes like cytochrome P450 that helps to break down those nasty compounds. At the population level, genetic diversity in the grouse genes that code for those enzymes is thought to reflect an ongoing evolutionary arms race between the birds and the plants. The plants evolve to get more toxic than the birds respond by evolving ways to tolerate that toxicity. And round and round it goes. I should mention that microbes in the guts of sage grouse may also play a role in detoxifying sagebrush secondary metabolites. Animal prey, like insects, are only a small part of the adult sage grouse diet. Young chicks, however,

feed on invertebrates like ants and beetles for the first few weeks of life. They need all that protein to fuel the fast growth of their little tiny bones and their muscles. Interestingly, Unlike other grouse and most birds in the family phasianity, sage grouse do not have a gizzard. Remember that the gizzard is a thick, muscular part of a bird's stomach that grinds and crushes food, often with the help of some swallowed grit or small stones. The gizzard works sort of like teeth since birds don't have the ability to chew. So, without a gizzard, a sage grouse can really only eat soft things, like leaves, flowers, and buds.

When it comes to finding food, sage grouse are very much creatures of the open ground. Foraging usually happens in the morning and again from mid-afternoon into evening. They walk around among the shrubs, picking through low-hanging leaves, buds, and flowers, and snapping up the occasional insect. Within a stand of sagebrush, grouse often pick individual plants with higher protein content and fewer toxins. Of course, sage grouse aren't only out there looking for food. They're also trying not to become food.

If you're a large, tasty bird walking around on open ground, that makes you a target for predators. And predation is the leading direct cause of death in sage grouse. Coyotes, bobcats, and badgers take a toll. And so do raptors, falcons, hawks, and eagles. Nest predators include coyotes, ravens, magpies, and maybe even squirrels. And we humans have indirectly tilted the balance in the not-good direction in favor of the predators. Roads, fence lines, and other edges created by development give predators easier access

to sage grouse habitat. For example, fences and power lines make great perches for raptors. Among the grouse themselves, risk isn't evenly shared. Males strutting around during their courtship displays are especially exposed. Their noisy, chest-popping displays make them highly conspicuous to hawks and eagles. Females, on the other hand, are most vulnerable when nesting, when they're sitting tight on a clutch of eggs. And hey, since we're talking about courtship, nests, and eggs, let's move on to look at breeding behavior in sage grouse. Many birds I've talked about on the podcast are monogamous.

In monogamy, one male pairs up with one female for one or more breeding seasons, and they raise a family together. Sagegrouse do things quite differently. Their breeding system is not monogamy, but polygony. Polygony means many females. A single male mates with multiple females. At the same time, many other males in the population may not mate at all in a given season, if ever. So mating success is unequal among males. On the communal display grounds, known as Lex, only a few dominant males achieve most of the matings. Now that word, Leck, L-E-K, is really important.

when you're talking about the biology of sage grouse. The leck is a place. It's sort of like a dance floor, or a stage, or an arena. It usually has less herbaceous and shrub cover than the surrounding habitat. Leck sites can include broad ridgetops, grassy swales, dry lake beds, valley bottoms, exposed knolls, or disturbed areas like cultivated fields, air strips, gravel pits, roads, recently burned sites, and haunted Indian burial grounds.

Lex are typically found within or adjacent to denser sagebrush stands, where the sagebrush is usually low and sparse, no more than one foot or 30 centimeters tall. A lex site is often used by grouse year after year. Some have been active for at least 75 years. This is a great situation for us birders because we convince, visit a known Leck site to witness the amazing behaviors of these iconic birds. In early spring, between late February and May, males gather at the Leck and start displaying with their Statue of Liberty Tales and their yellow air sacs.

And they make those plop, whistle, and coo calls we listened to earlier. All this frenetic activity attracts females. Once there are some female spectators at the Leck, some female judges, the males go into hyperdrive, making their strutting displays over and over. I'll put a link in the show notes to a BBC video clip of this courtship, this lecking behavior. If you watch the video, it's a little odd because at one point a baseline kicks in, and it turns out it's the song Around the World by Daft Punk. Now that song has one of the greatest music videos of all time, in my opinion, and I really like it.

But yeah, not what I was expecting while watching a video about Sage Krause. So the males strut and make their calls, but the females are the ones with all the power. A female chooses which male she's going to mate with. And the preferences of the females, for the loudest calls, the biggest yellow air sacs, the most impressive tail, or the fluffiest white rough feathers, those preferences lead to the exaggeration of such male sexual traits over many generations. That's sexual selection, baby! For greater sage grouse, the dominant male claims and defends the main stage, the center of the leg. This is an area about 32 feet or 10 meters in diameter.

That's where most of the females congregate. Subdominant males strut around outside of that prestigious central area. It's like they're on the side stages at a music festival. They might get a little attention if they're lucky. Later in the breeding season, there are also yearling males that show up. They have the lowest status and tend to take up positions on the outermost edge of the leck. In our music festival analogy, the yearling males would be vaping in the parking lot asking to buy tickets from anyone walking by.

But there is hope. There's some social mobility. in sage grouse. Males can gradually work their way closer to the center of the leck over time, both within a season and from year to year by filling vacancies left by other males. The dominant male in the center typically mates with approximately 80 to 90% of the females. In one example, a male was recorded mating 37 times with 37 different females in just 37 minutes. and I think we all know what number that bird would wear on his basketball jersey. I should point out that leck breeding, lecking, is not unique to sage grouse.

A fair number of other birds across multiple families do something similar. Wild turkeys breed in lex. So do birds of paradise, mannequins, and cock of the rock. Wait, how do you make that plural? Cock of the rocks? No. Cockes of the rock? Cox of the Rock, yeah, that's probably it.

Anyway, lecking is fascinating. I'll very likely dedicate a podcast episode to that topic in the future. In this leck breeding system, you have one male mating with multiple females, right? So, maybe it's not surprising that only the female is involved in incubation and care of the young. After mating, the male is done with his part. That's why the female's plumage is camouflaged. she needs to blend in with her surroundings to keep herself safe and to keep her eggs and chicks safe. She spends most of her time on the ground after all. Females actually select their nest sites

one to two weeks before mating. The bull-shaped nest is usually placed under sagebrush with an understory of grasses and forbs. This setup provides concealment from predators. And the nest often has at least two unvegetated sides, or openings, possibly as escape roots from predators. The female lines her nest with leaves, including sagebrush leaves, as well as grasses, small twigs, and feathers that she has plucked from her brood patch. The average clutch size is six to ten. The eggs are buff or olive color, and they're speckled with little chocolate brown dots. Incubation lasts about a month. Females take short breaks to feed during incubation, often in the morning and late afternoon or evening.

And then the baby sage grouse hatch. As with most species in the family Fazianity, hatchling sage grouse are precocial and painfully adorable. The chicks are covered and down at hatching. They're all fuzzy looking. Their down has a modeled pattern featuring spots of black, brown, buff, and white. And this makes for great camouflage. The little fuzzy balls can feed themselves soon after hatching, and they leave the nest with Mom shortly after as well. But the brood usually stays near the nest for a while. They need adequate cover and lots of forbs and insects to eat. As the chicks mature, Mom moves them to areas with more moisture, like stream beds, wet meadows, or irrigated fields. These places have more succulent vegetation and more insects,

especially during dry conditions. The chicks can actually fly short distances within two or three weeks, and they can make sustained flights when they're five to six weeks old. And the youngsters are largely independent by the time they complete their first molt at 10 to 12 weeks of age, usually by September or October. Lifespan in sage grouse is about three to six years, but some lucky individuals may live up to nine years or so. In terms of percent survival from one year to the next, females have slightly better odds.

Probably because males expose themselves so conspicuously during the breeding season. What with all the strutting and noise making? So more males are taken out by predators. Sage grouse are amazing birds. They're icons of the West. These poison-eating, tree-hating, pointy-tailed bull-feasants are beautifully adapted to life in the sagebrush step. But that very specialization, which has been a key to their success for at least 1.6 million years, that specialization ties them inseparably to an ecosystem that's rapidly disappearing.

A U.S. government report from 2022 revealed that an estimated 1.3 million acres of sagebrush habitat, is being lost every year. That's 0.53 million hectares. But even in the face of that, there is hope for these birds. All is not lost. There are still vast areas of core sagebrush habitat that we can defend,

and a lot of degraded habitat that could be restored. With ongoing collaborative conservation efforts on multiple fronts, like the sage grouse initiative, we can still save the sage grouse and the ecosystem they call home. And there you go. A little info on the two species in the genus Centro Circus. I myself have not seen a sage grouse yet. I've been in sagebrush habitat plenty of times, but I've never gotten lucky. And I haven't made the effort to go visit a leck. That is something

on my bird bucket list for sure. I mean, we have sage grouse right here in my home state of Oregon. I just got to make a plan and get out there. As always, I want to throw out a massive Brobdingnagian thank you to all my supporters on Patreon. And a big welcome to the newest members of my community there. Randy Vipond, Jill E, Zesty Turnip, Lauren Taylor, Nicole Servi McKeever, and Lisa Fox. Sorry if I mispronounced any of your names. Thank you all so much for the amazing support. If you are interested in becoming a member of the Science of Birds community,

you can check out my Patreon page over at patreon.com slash science of birds. And there's also a support the show link in the show notes in your podcast player app. If you have something you'd like to share with me, please go ahead and shoot me an email. Maybe you have a story about sage grouse, or you want to list your favorite smells, or you want to tell me what number you have on your basketball jersey and why. In any case, my address is Ivan at Science of Birds.com. It might take me a while to get back to you, but I probably will. Again, this is episode 122.

You can check out the show notes for the episode, along with some photos of Sage Grouse, on the Science of Birds website, Scienceofbirds.com. I'm Ivan Philipson, and true fact about me, some of my other favorite smells are coffee beans, orange blossoms, lavender, and the scent of dry, sun-warmed pine needles that blanket the forest floor, especially up in the mountains. Good stuff. Thanks for listening, and I'll catch you next time. Cheers. Oh, and seriously, I cannot stress this enough. If any prairie dogs are trying to get your attention by barking or making chirping noises, whatever you do, don't encourage them.

look them in the eye. Just ignore them, and with any luck, they'll lose interest and leave you in peace. Thank you.