Curlews, Sparrows, and the Ecological Trap

Ari Daniel: Hey, I’m Ari Daniel, and this is Threatened, a new show from BirdNote about answering the call to protect the birds and places we love. In this episode, we travel to Idaho, where native grasslands were once a rich mosaic of plantlife that supported a diverse cohort of birds. But as European settlers moved west, they converted those rich grasslands into farm. Today, very little native grassland habitat remains in the Intermountain West. So we’re about to tag along on a quest to search for Long-billed Curlews, find a patch of restored habitat containing a bounty of grassland birds, and speak with the people working to protect and expand what’s left of this unique habitat.

This episode comes to us from Monica Gokey in west-central Idaho. She’ll take it from here.

Monica Gokey: OK… it’s a sunny, windy day outside Indian Valley, Idaho. Looks like we’re by an alfalfa field. When the wind blows, all this grass and alfalfa waves. It sort of looks like waves on the ocean.

Monica Gokey: I’m here to meet research biologist Heather Hayes from the Intermountain Bird Observatory at Boise State University. It’s mid-June, and today is the hatch date for a Long-billed Curlew nest she’s been monitoring.

Heather Hayes: Today is her hatch date, so, um, so we’re hoping that it’s on target.

Monica Gokey: The Long-billed Curlew is an iconic grassland bird species in the Intermountain West. It’s a large bird, about the size of a chicken or a small duck, with a long, slender bill that curves down from its face. Female curlews sit on the nest during the day, while the males take the night shift. It’s the female Heather’s looking for.

Monica Gokey: What are you hoping to see?

Heather Hayes: I’m hoping to see some chicks! [laughs] There were four eggs the last time I checked. And hopefully, if the parents have been able to keep the predators away… they will be there with healthy chickies. Let’s go out there and check it out.

Monica Gokey: Four fully feathered little chicks! Heather gives me a run-down of the game plan.

Heather Hayes: What we’re going to do is, as we approach — when we get, probably to about 20 meters or so, we’re going to slow down.

Monica Gokey: We wade out into a field of thigh-high alfalfa, gauging our proximity to the nest against Heather’s GPS. Heather doesn’t want to flush the female curlew off the nest, if possible. Hatch day is stressful for curlews, and both parents are typically on high guard for any intruders.

We walk for several minutes.

Monica Gokey: I think we must be getting close...

Monica Gokey: Heather motions for me to stop.

Monica Gokey: We’re right up on the nest… but we don’t see it. Nor do we see a curlew. So we’re just very slowly looking around us.

Monica Gokey: Heather finds the nest and we crouch down over it. And there are four green eggs, speckled brown. They’re camouflaged beautifully against the brown earth and green alfalfa. The eggs are large — they’re bigger than chicken eggs. Heather picks one up and looks it over. She shows me several small cracks in one part of the egg.

Heather Hayes: So the eggs are starring, which is when the chicks start to break out of the egg. But what’s concerning me is there’s no curlews around.

Monica Gokey: Heather gently lays a hand over the eggs.

Heather Hayes: They feel pretty warm!

Monica Gokey: So this is a good outcome?

Heather Hayes: It’s tough to say. I’m a little concerned that perhaps they abandoned.

Monica Gokey: After quickly checking all four eggs, we leave the nest site, taking a different route than we used coming in. Heather says birds like magpies and ravens, which can prey on curlew eggs, will actually notice a trail like ours through tall grass — or in this case, alfalfa — so researchers always take circuitous routes to and from the nest sites, different on every visit.

Back at the car, Heather tells me what we saw was perplexing.

Heather Hayes: With the chicks apparently hatching out at this point, I would expect that one of them would be here defending. So that’s why I’m a little bit on the fence as to what might be going on.

Monica Gokey: The eggs were warm! That’s hard for Heather to ignore. But she keeps coming back to the fact that we didn’t see any adult curlews. This is what Heather was expecting to hear at the nest:

[Adult Curlews Mobbing]

Monica Gokey: That’s the sound of screeching adult curlews. Long-billed Curlews don’t have sharp beaks or talons. So when it comes to defending their nests, they rely on sheer bravado. They dive-bomb would-be predators, screeching madly, which is a signal to other curlews in the area to come join the defense. The behavior is called mobbing. Heather’s been mobbed countless times. The birds never actually make contact — that would be way too risky to their fragile beaks. The intended effect is intimidation. And Heather says it works — being mobbed is intense.

But today… no mobbing. No female sitting on the nest. And Heather doesn’t know what to make of it yet. So we do what field biologists have done for ages. We sit, and we wait, and we watch.

[Music Rises]

We gaze out at the alfalfa field, gently waving in the breeze. This field is not a curlew’s natural habitat, obviously. But it works.

Heather Hayes: In the history of their known habitats that they prefer, you know, it’s that grassland area where it’s low in the beginning so they have a nice view of any predators coming upon them. And then as that — as the grass starts to grow, it provides concealment opportunities for the chicks.

Monica Gokey: I see how an alfalfa field replicates that. It’s short in the beginning of the growing season like a native grassland would be. View of predators? Check. And then it grows taller as the birds need concealment from predators. Also check. Before meeting Heather, I’d been surprised to learn that southwest Idaho was once some of the densest curlew breeding habitat in the entire United States.

Heather Hayes: It used to be. It used to have the biggest population of Long-billed Curlews. And now in this short — about forty-year span — they're at about a 95 percent decline. That’s when alarm bells really started going off.

Monica Gokey: A 95 percent decline over four decades is steep. Very concerning. It’s something the Bird Observatory’s been trying to puzzle out for more than a decade now… and every year, scientists like Heather undergo the herculean task of monitoring these birds in the field. They find curlew nests, they trap and attach transmitters to birds, and then monitor those birds on their migration. And — on days like today — scientists are cataloging nest success. Do the eggs hatch? Do four more itty bitty curlews arrive and take on the world?

Nearly five hours after first checking the nest, Heather calls it a day. We start driving away. And then… Heather’s brake lights flash red ahead of mine. She has eyes on the transmittered male curlew. His nickname is Dozer. I get out of my truck and walk up to Heather. Sure enough, male curlew! Straight ahead! He’s sitting in the middle of the road, preening himself, cool as a cucumber.

Heather Hayes: The only other thing I can think of is maybe if he is on his own, he doesn’t want to cause attention?

Monica Gokey: Uh oh… there’s a side-by-side coming.

Heather Hayes: Oh yeah… he’s going to flush up.

[Dozer flushes: coo-EE! coo-EE!]
[SUV loudly drives by]

Dozer takes flight as the off-road vehicle whizzes by. That sound he made — coo-EE! coo-EE! — Heather calls it the curlee call. It’s Dozer’s way of saying, “hey, I’m here! I’m here!” to other curlews in the area. Heather and I hang around for another hour hoping to see Dozer return to the nest, but we don’t see him again.

Heather Hayes: I think my heart is saying that the nest has failed. I truly believe that in almost all my cases that at this stage in the game, those chicks are obviously starting the process of hatching. I should have a lot of angry birds right now mobbing us. And we don’t have that.

Monica Gokey: Heather pegs it at 80-20 odds the nest has failed. But she’s not throwing in the towel yet.   

Heather Hayes: So I think what I’ll do is give it a rest for tonight, see if maybe he’ll come back and sit on those eggs tonight and see if I have him on the nest in the morning. And… be hopeful,” she shrugs.

Monica Gokey: The following morning, I get a text from Heather.

[Text Tone]  

The eggs are cold and unhatched. It’s officially a nest failure.

[Music Rises]

Several hundred years ago, Long-billed Curlews were not nesting in alfalfa fields. They were nesting in the rich, diverse grasslands that covered the Intermountain West — from eastern Oregon and Washington, through Idaho, all the way over to western Montana. Today, the remnants of these vast grasslands have different names. There’s the Zumwalt Prairie in eastern Oregon. The Palouse Prairie. The Camas Prairie, named for the purple-flowering camas plant that was a major food staple of Iindigenous Peoples in the area.
 
Let’s rewind to pre-settlement. I’m driving into north-central Idaho, and the scenery is mostly yellow. Truly! There is actually not a speck of green visible on some parts of this drive. What I’m seeing is wheat. Thousands upon thousands of acres of it. Ready for harvest.
 
Dr. Angela Sondenaa is a biologist for the Nez Perce tribe, or the Nimipuu people. There’d just been a coronavirus outbreak in the area, so we meet outdoors at a park off the highway. Angela tells me what tribal lands used to look like.

Angela Sondenaa: So before settlement, the Nimipuu lands — and especially the grasslands — were a very diverse garden. And so most people when you tell them ‘oh it was a grassland,’ they have a picture of a pasture or a hayfield, and that’s not what these were like. These were very, very diverse, forb-rich communities with grasses as the base of the community… but abundant forbs.

Monica Gokey: Forbs are leafy, flowering plants — not grasses. They’re things like mariposa lilly, arrowleaf balsamroot, lupine and goldenrod.

Angela Sondenaa: And our grasslands, too, are not flat! They’re not like the Great Plains in the central part of the United States. These are rolling hills. And so you’d get subtle microclimates that would occur. And so you’d get a different complement of species in different areas. We also had low-lying areas that were wetlands! And wet, meadows that had a totally different compliment of forbs and grasses and rushes in them. So it was a very diverse landscape.

Monica Gokey: And what changed?

Angela Sondenaa: What changed, unfortunately, is when this area became discovered by European settlers, they quickly realized that the soils here were very rich, and very good for farming. And so a lot of the prairies, a lot of the large, open, ponderosa pine grassland communities were all converted to annual agriculture. And so most of the prairies were destroyed and turned into what is now one of the biggest wheat-growing regions of the country.

Monica Gokey: As a result of this grassland to farmland conversion, very, very little native grasslands remain. Angela’s team, for example, has surveyed prairie remnants on Nimipuu tribal lands, and less than 0.5% of lands surveyed are in-tact prairie. But in those remnants? A wealth of knowledge about the native plant communities that once defined this area.

Angela Sondenaa: We came up with a list of about 30 species that we just considered core. If you have this, this is sort of the basis of your prairie. And there are three grasses: bluebunch wheatgrass, Idaho fescue, and prairie junegrass. We had two shrubs, rose — native rose — and snowberry. And then a whole suite of forbs. Things like goldenrod, and some of the mariposa lilies came up on that list. And so we’re starting to get a pretty good feel for what the basic, consistent species are for our prairies. And it was interesting, too — some of the species that we have considered rare plants really were very common in the remnants. And so that tells me they’re rare because of habitat loss. They’re rare because humans have destroyed most of their habitat. It was a little surprising to us. But that’s what happens when you start looking at these things on a larger scale.

Monica Gokey: I’m still in north-central Idaho, about an hour north of where I met Angela, when I finally find some prairie. We’re on the historic turf of the Palouse Prairie. Kas Dumroese, a local landowner, is showing me around.

Kas Dumroese: So we’re standing on a 50-acre island of habitat that’s not dryland wheat, garbanzo beans, or peas.

Monica Gokey: Some of Kas’s land is intact Palouse Prairie. Never been plowed. But most of his land has been retired from the kind of agricultural production that surrounds this property. For nearly thirty years, he and his wife have been trying to revert these retired ag lands to native prairie, mostly by seeding native plants. We walk up to the butte behind Kas’s house. We’re wading through what was once a pasture. It’s mostly agricultural grasses… until we get to the fringes.

Kas Dumroese: If we look down, we’ll see that the Palouse Prairie is trying to stage a comeback. Right? Here’s lupine coming in. Lupine in front of us, and as we walk down here we’ll see several species that are slowly making their way back into this grassland.

Monica Gokey: What we’re seeing is the fruition of Kas’s restoration work: Seeding native plants where they belong and then hoping they take root and spread on their own. We see native plants that should be here!

Kas Dumroese: There’s balsamroot...

Monica Gokey: Willowherb…

Kas Dumroese: Hairy Albert…

Monica Gokey: Lomatium…

Kas Dumroese: Dogbane…

Monica Gokey: Wild onion…

Kas Dumroese: Sticky geranium…

Monica Gokey: Truly, it’s there! Flickers of native Palouse Prairie. The in-creep of these native plants into an old grass-dominant pasture is a slow process. So slow. On the one hand, you have Kas who’s seeding these plants, trying to nudge them along. But on the other, you have totally new challenges here.. — chiefly, the weeds.  

Kas Dumroese: Weeds are just the most depressing part of it. Because not only do we have a lot of them now, it seems like every year we have one or two new ones.

Monica Gokey: The weeds here fall into two categories: There are the invasive, or exotic weeds — things like cheatgrass, ventenata and skeletonweed. And then there are the agricultural grasses. Neither is native to the Palouse. But Kas says the weeds aren’t going away anytime soon.

Kas Dumroese: Getting all the way back to a pure Palouse Prairie with no invasive species in it? Probably not realistic. So, given this new suite of players in the system, again, how do we alter the trajectory to get us to a state that is more Palouse Prairie-like. Because what we’re really trying to do is to get that function of Palouse Prairie back.

Monica Gokey: When you have this kind of a situation — land whose plant community is part native prairie, part exotic weeds, and part agricultural grasses — you have what biologists call a novel ecosystem. It’s something new: novel. And for birds, novel ecosystems can totally work! But they don’t work for all birds equally.

Ornithologist Carl Lundblad, who’s out here with me and Kas, explains. He brings up the Grasshopper Sparrow, a wee little grassland bird that sounds uncannily like... a grasshopper. It’s a bird that needs intact prairie.

Carl Lundblad: Grasshopper Sparrows in the West really seem to cue in on lush grasslands that also include a little bit more of that structure where they have those advertisement sites, those perches that they can get up on. To draw a contrast with the Savannah Sparrows, I don’t know what mechanism makes a hayfield tolerable to Savannah Sparrows, but they don’t seem to mind just a monoculture of grass… and it doesn’t have to be native. It can be alfalfa. It can be a hayfield. They’re not picky like the grasshopper sparrows and some of the other species are.

Monica Gokey: Savannah Sparrows? Total generalists. Thriving in the novel ecosystem. But not the Grasshopper Sparrows, and some of these more specialist grassland birds, like Vesper Sparrows and Clay-Colored Sparrows. They prefer the original habitat… or what little remains of it. There are issues of scale here, too.

Carl Lundblad: When you look out across the landscape and realize these tiny fragments are all we have left, there’s a whole ‘nother suite of species that these fragments aren’t enough to support, and that were probably a big part of the Palouse, historically. So things like Sharp-Tailed Grouse, Loggerhead Shrikes. Ferruginous Hawk is a great example. So there’s some species that still cannot thrive on this landscape when all we have left are these little tiny scraps of habitat.

Monica Gokey: This hits at why Kas and his wife are undertaking this huge prairie restoration project, at their own expense, I have to add.

Kas Dumroese: We don’t have very much prairie left — and so saving and preserving, and conserving and restoring, observing what we do have left is important just to maintain the biodiversity of that almost extirpated ecosystem.

Monica Gokey: We dip into the original Palouse prairie on our way back to Kas’ house — that beautiful messy wildness we saw when we first arrived. The diversity is just bonkers here! We hear so many different birds — a Pygmy Nuthatch, Western Wood Pewees, Spotted Towhees, chickadees and kingbirds. And there are also so many different plants here.

Monica Gokey: And what is that?

Kas Dumroese: Gentian. Not very many out here. Oh my gosh! There’s a huge one behind you!

Monica Gokey: Gentian is blooming a cheerful purple right now… which points to another key function of diverse, native habitats: Pollen supply throughout the growing season. It’s late August, and the gentian is just now blooming.

Kas Dumroese: Can you see this little itty bitty pollinator in here? There’s a little itty bitty bee in here.

Monica Gokey: Oh yeah!

Kas Dumroese: And look at how much pollen he has on his hind legs! He can’t even move, hardly. He’s so weighed down he can’t even get out.

Monica Gokey: He’s got the big pollen-pants on!

Kas Dumroese: He’s got big pollen-pants on… he’s stuck!

Monica Gokey: Having plants that bloom at different times of the growing season bodes well for a strong insect community. The healthier the insect community…? Well, you probably get the picture. Diversity begets diversity… and it’s a win for birds.

On the walk back to the house, I consider how some elements of the novel ecosystem function in the same way as the native ecosystem. But it’s hard to know which parts work for birds, and which don’t. Carl mentions an idea that immediately clicks: The ecological trap.

Carl Lundblad: The concept of the ecological trap is when the cues, the approximate cues, an animal uses to select habitat, are no longer predictive of their fitness, their survival and their reproductive prospects in the way they used to be. And ecological traps are driven by anthropogenic changes.

Monica Gokey: Basically, it’s what happens when a bird is doing everything right — it’s relying on behaviors developed over generations of evolution. But, those processes fall apart when we, humans, dramatically alter the landscape. I tell Carl about visiting the curlew nest with Heather in an alfalfa field. Totally not a curlew’s natural habitat.

Carl Lundblad: So the curlews are a really good example. You can imagine a curlew or another migratory bird flying across the landscape might see an agricultural field. And to the animal it looks just like the habitat they evolved to nest in and settle in. So they select that habitat. They initiate a nest. But then the farmer might then come in and mow or harvest that field before the nest has fledged or before that bird can be successful nesting in that location. So while their evolved habitat selection behaviors are working correctly, those evolved cues are no longer predictive of their reproductive success. And that’s what we call an ecological trap.

Monica Gokey: So how do we know what those traps are? The short answer is, we don’t. We only find those traps by paying attention. Very close attention.

Okay, let’s travel back south to see if we can determine why curlews are struggling. Remember, Long-billed Curlew populations have plummeted 95% over 40 years at the Intermountain Bird Observatory’s study site in southwestern Idaho, which had once been some of the densest curlew breeding habitat in the entire U.S. This is a different study site than the alfalfa field.

Here’s research biologist Heather Hayes again. She’s the one who showed us the nest in an alfalfa field… the one that failed. She says when the curlew study first started, scientists were looking to habitat as a possible reason for decline.

Heather Hayes: Obviously there was a lot of urban development. A lot of habitat degradation going on in the public lands. You know, also things like climate. So when they’re on their wintering grounds you know, what types of habitats are they needing to survive … and even their stopover points through their migration — are they having trouble somewhere in between there?

Monica Gokey: Enter, the transmitters. They’re not cheap. They cost $3,000 a pop, plus $1,000 or more annually in data fees, each. But they let scientists know where a bird is at all times.

Heather Hayes: When we started putting those transmitters on, it kind of changes the dynamic a bit, because if a bird were to go down, we have equipment that can hear the signal inside the transmitter. So we can actually go track down that bird, know its last known coordinates, and then start searching.

Monica Gokey: Idaho’s Department of Fish and Game was one of the underwriters of the curlew transmitter study. They have a Wildlife-CSI type of laboratory, and they said, “Hey, send us your dead birds… we’ll try to see what’s happening to them.”

Heather Hayes: The interesting thing is when we would usually find them, they were usually tore up like a predator got them — like a coyote or a badger or something. You start to think, if all these birds we’re finding are in pieces, there’s a predator issue, and ‘How do you control predators?’ and ‘Can you control predators?’

Monica Gokey: Dead curlews are food for scavengers. Before the transmitters, when scientists would find dead curlews, they’d typically been eaten on by animals like coyotes or ravens. In 2013, the first transmittered bird of the study goes down, and the Bird Observatory sends it to Fish and Game for a necropsy.

Heather Hayes: And so the first x-ray we got back was of uh one of our curlews that had gotten shot. And you could see the metal very clearly.

Monica Gokey: So it was a surprise to you?

Heather Hayes: Ohhhh it was very surprising. It was a game-changer, I think for all of us in the program because you start taking bird after bird after bird in. And, you know, when the majority of the birds are coming back positive for metal in the x-rays… that was a game-changer. And made us realize that we need to start educating the public.

Monica Gokey: How did it make you feel when you learned the the birds were not dying naturaly? That they were just being shot?

Heather Hayes: For me it was hard. It’s hard for anybody I think, because it’s not a species that you’re allowed to hunt. It’s protected under the Migratory Bird Treaty Act. So a lot of people will say, ‘Well, you need to go out and educate hunters not to shoot them.’ But the fact of the matter is hunters get their license by going through classes and they learn — they know what they are and aren’t allowed to shoot.

Monica Gokey: People aren’t hunting curlews, like for food. They’re just shooting them. Heather says, like so many things, it’s likely just a handful of people making poor decisions. It adds up, though. Scientists anecdotally knew birds were being poached at their study site because they'd sometimes find shot curlew carcasses. But it wasn’t until the transmitters arrived that they realized the scale of the problem. Over a five-year span of the study, a third of transmittered curlews were shot. Thirty-three percent. It was a significant source of mortality.

A population can’t hemorrhage adults and thrive. Curlews are long-lived, and that helps hedge what’s already a naturally low nesting success rate for the species. Say a curlew lives fifteen years: if it’s poached in its reproductive prime, maybe as a six-year-old, for example — that’s nearly ten years of future progeny the population misses out on. So that 95 percent decline over 40 years? Yeah, totally possible.

After hearing Heather’s stories about the shooting, I kind of wanted to see her study site for myself. It’s about a half-hour south of Boise, Idaho. Wide open space. It’s a-hundred-and-two degrees out, and I’m several miles down a gravel road

Monica Gokey: Ohhh I can see it now. There we go… When Heather first told me how to get here, she gave me directions to the tune of, ‘Drive down Pleasant Valley Road, and then follow the trigger trash,’ and I kinda thought those were crummy directions… but now that I’m here, it totally makes sense.

Alright, so you look on the ground, and it is just… picking up a couple, shotgun shells and rifle casings everywhere. When I first pulled up I thought I’d try to count to give a sense of the scale, but there are way too many to count.

Monica Gokey: Heather told me her whole job changed after the poaching revelation. She still works the summer season as a field biologist, but the rest of the year, she’s on the road doing curlew education. She talks to classrooms, hunter ed classes — pretty much any place that will have her. Those years of public outreach finally seem to be working. 2019 was the first year no transmittered curlews were shot. And, results are newly in, the same goes for 2020. The obvious caveat here is that this doesn’t tell us anything about whether non-transmittered birds are being shot — which are far more numerous on the landscape than transmittered birds. But it’s a glimmer of hope.

Because the vast majority of Intermountain grasslands have been plowed under, most the birds here are trying to make do with what they have, habitat-wise. And they’re not wizards. Evolution never prepared curlews to foresee things like when the alfalfa would be harvested, or whether a great-looking nesting spot is in the same area as an avid recreational shooting community.

If science is our currency of credibility, this work matters when it comes to saving birds. It’s only by finding the ecological traps that we can remedy them. This means we have to ask ourselves some hard questions… chiefly, do we care enough to figure out why some birds are struggling. And if so, what, if anything, are we willing to change? Good science informs better management. The more we know, the better we can do.

Ari Daniel: Thanks for joining us for this episode of Threatened. If you want to learn more about what you can do to help grassland birds, visit BirdNote.org and check out our show notes. Next week on Threatened, producer Molly Segul takes us to the Fraser Estuary in British Columbia, where Western Sandpipers flock by the thousands to fuel up during their long migrations

It’s so mysterious the way that they move in their big cloud

Ari Daniel: And she finds that a commercial port expansion could put an important food supply for those birds in danger.

Diatoms are critical. They’re the crux of the entire food web.

Ari Daniel: Subscribe now so you don’t miss it. Also, give us a rating in Apple Podcasts, since it helps other listeners find the show. And stay in touch with us on social media by following BirdNote on Facebook, Instagram, and Twitter. BirdNote is an independent nonprofit public media organization. If you like what you hear, help support our programming. Visit our website, BirdNote.org, and click the “Donate” button.

This episode was produced by Monica Gokey and me, Ari Danielm, with support from the BirdNote team. Thanks again for listening, and see you next week.