Thumbnail image: Vladimir Pravosudov
[Sarah Wagner] Welcome to today’s webinar from the Cornell Lab of Ornithology. My name is Sarah and I’m on the Visitor Center team at the Cornell Lab, and I’ll just be facilitating today’s conversation about some really exciting new research on chickadee memory. With us today, are Carrie Branch and Ben Sonnenberg. Carrie is a postdoctoral fellow here at the Cornell Lab of Ornithology. Hi, Carrie. And Ben is a PhD candidate at the University of Nevada, Reno. Welcome Ben. We’ll hear more from them in a little bit.
Thank you so much for taking the time to be here with us. We’ll be hearing so much more from our panelists soon after just a few announcements that I need to make. So as I said, today’s webinar is hosted from Ithaca, New York. And I want to read a statement acknowledging the Indigenous land that of the original inhabitants of this area.
Cornell University is located on the traditional homelands of the Gayogoho:no, the Cayuga nation. The Gayogoho:no are members of the Haudenosaunee Confederacy, an alliance of six sovereign nations with a historic and contemporary presence on this land. The Confederacy precedes the establishment of Cornell University, New York state, and the United States of America. We acknowledge the painful history of the Gayogoho:no dispossession and honor the ongoing connection of Gayogoho:no people, past and present, to these lands and waters.
For those of you who are not familiar with the Cornell Lab of Ornithology, it’s home to a community of researchers and supporters from around the world who appreciate birds and the integral roles they play in our ecosystems. Our mission is to advance leading-edge research, education, and citizen science that help solve pressing conservation challenges.
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All right, with all of that being said, we can get started. All right. So there are Carrie and Ben back. Carrie and Ben, thanks so much for being with us here today. I am really excited to learn more about your research and to share it with our audience. You both seem to be really great teachers. Would you introduce yourselves to us and tell us a little bit about your background? Carrie, you can go first and then Ben.
[Carrie Branch] Sure. Let me share my screen real quick. So hi, everybody, and thanks for having me, having us on this webinar today. We’re excited to share some of the work that we’re doing and the incredible abilities of these little tiny birds we see all over North America. So I’m actually originally from Tennessee where I did my bachelor’s degree in psychology working with Todd Frederick. And that’s really where I fell in love with these little chickadees and tip my species that we know so well.
And so there I studied communication and signaling, as well as mixed species flocks as an undergrad. Following that, I went on to do my master’s degree at the University of North Carolina, Wilmington, where I looked at rat cognition with Doctor Kate Bruce. And that was strictly in the laboratory. And I really liked the work and the questions we were asking, but I was itching to get back into the field really bad.
So when I decided to go on to pursue my PhD, I actually chose to go to the University of Nevada, Reno where I worked with Dr. Vladimir Pravosudov, and this really melded the two worlds of research that I was interested in, both the cognitive side of things because he studies cognition and in the wild and in chickadees, and then the chickadee side of things, and being able to actually look further into their vocalizations and the evolution of the different signals that they use.
And after graduating there in 2018, I received a postdoctoral fellowship to come here to the Lab of Ornithology. So I’ve been here since November of 2018, which seems crazy now. And I’ll actually be starting an assistant professor position at the University of Western Ontario in July. So that is my trajectory so far. I’ve always loved animals. And when I found out that animal behavior was a field I could go into, it was like, yes, this was made for me. And so that’s my story.
[Ben Sonnenberg] Yeah. Well, hello, everyone again. Yeah, my name is Ben Sonnenberg. I’m originally from Montana, Bozeman, Montana so I’m a Westerner. And I grew up out in the woods chasing all sorts of wildlife, but I first really were attracted to birds and research around birds and behavior when I was an undergrad at Pacific Lutheran University in Washington State in the Pacific Northwest, and where I got to the ability to chase around Red Crossbills all over the Pacific Northwest recording their songs and their calls.
And that just lit a fire for observing birds in the wild and led me to other experiences and where I got to do research and work with sea duck species, like Spectacled and Steller’s Eiders up in Alaska, and then back in Connecticut with these Whistling Ducks. And Carrie asked me if that photo was photoshopped, it’s actually not. Those are all three Whistling Ducks who just loved me, I guess. But I got to do lots of education work with not only Whistling Ducks, but all sorts of other waterfowl species and a few raptor species in Connecticut.
And eventually came back West to Nevada where I am currently in my fifth year of my PhD program where I work on Mountain Chickadees in the wild. And it’s just an amazing experience working in the Sierra Nevada. And I particularly am interested in chickadees and their reproductive behavior and how that ties back to their amazing cognitive abilities, which we’ll dive into as we go.
[Sarah Wagner] Awesome. Thank you both. It’s always nice to hear how people arrive at where they are and all of the fun field jobs that you’ve been able to take part in along the way. So could you guys tell us a little bit more about what it is about chickadees that are particularly good at answering these questions for you two. Ben, you can go first and then Carrie.
Yeah, well, so chickadees are just a fantastic group of birds that are easy to study and convenient to study. And so we’re going to dive into all sorts of reasons of why specifically Mountain Chickadees a little bit later. But I first wanted to just introduce maybe a few familiar– reintroduce, I should say, a few familiar faces. And so Parids– and so Paridaes, the family that chickadees are in. And they are actually originate from an old world family.
And so these guys were native to Europe and Asia, and they crossed in and populated North America around four million years or so ago. And so this right here is a Blue Tit and a Great Tit, and so those might be common faces that I guess I was first introduced with on my grandmother’s tea towels or on Christmas cards. And those are two really well-studied birds in Europe. And those are relatives of chickadees.
And this little guy right here is a Willow Tit. And so Willow Tits are probably the closest common ancestor that came across from Siberia, from Russia, and colonized North America, and then diversified into the species that we know today. And if you could just pull up that, yeah, this is the overall distribution map of where parents live in North America. So across Europe and Asia, even into the subtropics of Africa and now into North America. But the only places that you can’t find these wonderful birds is Australia, Antarctica, and South America.
[Carrie Branch] Awesome so I wanted to go into a little more detail about our seven species that are located in North America. And so what you’re seeing here, which seems a bit overwhelming with all of the colors and pictures of birds, I’m sure. But this shows the geographic distributions or approximate distributions of each of these seven species.
And you might be saying, seven species, we have seven? We do. And so you’re seeing them all listed here. We’ve got the Black-capped Chickadee which has the largest range shown here in this skin tone color, didn’t think through how to say the names of the colors, here. And so you can see this really broad range, all the way up into Canada and Northern latitudes of the United States.
Then we have the Carolina Chickadee who’s down in the Southeastern areas highlighted here in green. We have our Mountain Chickadee, which you’ll be hearing a lot more about, highlighted here in yellow. And as you can see, it’s a member on the Western side, but mostly in the montane regions. And what you’re probably noticing is there’s a good amount of overlap in terms of range within all of these different species.
And that’s what I think is really fascinating, compelling about these guys, is like where one’s ecological niche drops out, the other picks up. So in the mountains here even you can see that the Black-capped Chickadee picks up where the Carolina Chickadee can’t really hack it, up in those colder areas of the Smoky Mountains.
Then down here, we have the Mexican Chickadee. And interestingly, it’s one of the only ones that really doesn’t seem to overlap much with the rest of the species. And so these are what are called our Black-capped Chickadee species, and they’re thought to be more closely related compared to these Gray-headed Chickadees over here on the left or my left side.
So what we’re seeing are the Gray-headed Chickadees which have a pretty small range up here in Alaska and Canada. Those are the ones most closely related to those Siberian tits that Ben was mentioning. And then we have our Boreal Chickadees, which are highlighted here in the blue. So we can see they have quite a large range as well. Although the range is large, they’re not as common as something like a Black-capped Chickadee would be.
And then finally, we have our Chestnut-backed Chickadees that have a rather small range, along this coastal region in purple here, and then somewhat here in the United States as well in Idaho. And so again, showing all of these different ecological niches and the niche space that they take up, which is essentially just the role they play within the ecosystem.
And with that, I wanted to also show again, this is a lot of information. But when we’re thinking about why chickadees have been mentioned, that a lot of work has been done in Europe on these other tit species like Great Tits and Blue Tits. But within our North American chickadee species, so they’re all listed here in this column, and I’ve just compiled some information. This is actually for a grant that I’m pursuing.
But they’re fascinating because they vary in so many ways that are interesting to folks that study behavior. So they vary socially, and since that their flock size varies across the different species, the degree to which they use an actual whistle song which we’re so familiar with, the classic whistle song Black-caps, and Carolina, and Mountain Chickadees, that actually varies quite a bit. So for someone who’s interested in vocalizations and communication, this is another compelling aspect of chickadee life history because that variation is interesting.
And the fact that they vary by location as well feeds into that how the environment might be selecting on these differences we see across all of these aspects, as well as caching behavior, which we’re going to talk a lot about today, whether or not they’re excavators, which is just related to– these guys are all cavity-nesting birds, and whether or not they actually have to excavate their own holes or if they’ll use secondary holes from woodpeckers and et cetera.
So most of them excavate, but a couple of species don’t. And you might notice that seems to be associated bit with whether or not they actually cache food, which again goes back, and we’ll talk a bit more about this about whether or not they cache, whether or not they’re in these harsher environments compared to milder environments. So you can see here with like the Mexican Chickadee, which would probably be the mildest environment of any of our chickadee species, they don’t cache and they’ve never actually been observed to excavate in the wild.
We also know quite a bit about their dominance hierarchies among each other. So these birds in instances where they overlap, they will hybridized. The Black-cap and Carolina Chickadee hybrid zone is the one that’s most studied. And we know something about their dominance interactions among each other as well.
So it’s really cool because these birds exist across the North America, lots of folks are studying them. They’re living in these areas all year round. They don’t move much. So it’s pretty easy to track them. They’re very vocal and conspicuous. And so all of these things come together. They’re actually really suitable in the lab as well. They do great in the lab. So all of this comes together to create this model system that we can actually study in the wild and ask all kinds of questions about animal behavior, and why they behave, and do the things that do.
[Sarah Wagner] That’s a cool system. Thank you for sharing that. That map with the range overlap, it’s really powerful to see all of that in one place, and this table is really great too. Could you guys, since we’re going to be talking a lot about Mountain Chickadees, maybe you could go ahead and introduce the Mountain Chickadee, tell us a little bit about their biology and where they live.
[Ben Sonnenberg] Yeah, so I can talk about Mountain Chickadees. Mountain Chickadees reside in Western North America as you can see by their range map here. And this is courtesy of eBird data. So all those eBird users out there, thanks so much for contributing. And you can see it their range stretches all the way up into Canada, down to even the Southeast Arizona, New Mexico, and then very much they inhabit the Rocky Mountains in the West like Montana, as well as the Sierra Nevada, where we study chickadees.
So we happen to study Mountain Chickadees. Our field site is located at Sagehen Experimental Forest which is North of Truckee, California in the Sierra Nevada. And that’s where our long term field site, which we work with Doctor Vladimir Pravosudov who is my advisor and Carrie’s collaborator and who established the system that we work in. And so we can move to the next one.
So here we just wanted to give you some visuals of what our field site looks like. And so this is a picture from several years ago in March. And so this just beautiful pictures, and this happens to be a blue sky day. But you can see just lots of snow surrounding the area. And this is one of our high elevation sites.
And this, it’s hard to see. But this is actually during a snowstorm. And so you can look at all the trees covered in snow, all these beautiful conifer trees. We have several conifer species up there that the chickadees really rely on for their pine nuts that they’re foraging on and that they cache for future consumption. But looking at this picture, you can tell that it’s a tough world up there. It’s cold. There’s lots of snow. And so these Mountains Chickadees have to have special abilities that we’re going to elaborate on that allows them to hack it, as Carrie likes to say, in such environments.
And how we go about comparing how chickadees do in different environments, is we can actually do this within our field site. You can do this across large spaces like latitudes as well. But there’s even detectable differences within our population of Mountain Chickadees that reside across an elevation gradient.
And so our elevation gradient is defined by a snow line, which is approximate elevation that during transitional months of the year, such as spring and fall months, precipitation is more likely to fall at high elevations as snow rather and at low elevations as rain. And that basically translates into high elevation environments having more snow, colder temperatures, and those qualities persist for longer periods into the breeding season.
And so chickadees at higher elevations have to essentially inhabit a slightly different environment, even more harsh environment than the chickadees at these lower elevations. And if you don’t believe me, these two pictures were taken at the same day several years ago in June, right Carrie? Yeah, in June several years ago. And so you can see both in June, chickadees are wildly nesting, and building nests, and laying eggs at this time of year. And you can see that they’re doing so in very different environments, with the high elevation environment still having lots of snow stick around.
[Sarah Wagner] Wow, that is pretty dramatic. So thank you for the little background on– thorough background on the Mountain Chickadee. The other big topic for today is cognition. So Carrie, could you unpack cognition for us quickly?
[Carrie Branch] Yeah, absolutely. So Ben just mentioned this. So this work we’re talking about was all thanks and a big acknowledgment goes to Dr. Vladimir Pravosudov at the University of Nevada, Reno because he started this field system. And you can actually, if you’re interested in the work more broadly, you can visit his website at chickadeecognition.com, and it will talk all about the various projects that he’s been involved in.
But when we talk about cognition, which feels like a weird abstract word, this is really the study of mechanisms by which animals acquire, process, store, and then use information that they gather from the environment. And so other ways we talk about this are things like perception, learning and memory, decision-making, tool use, things of that nature.
So when we’re talking about cognition, a lot of times folks will say, wait, animals have cognition? Of course, they do because they remember information and they use that information to adjust their behaviors in the future. So they absolutely have cognition. They’re gathering information. They’re processing it in their brain. They’re storing it in their brain. And they’re using it later to act on it.
And so cognition is this really broad topic, and cognitive ecology, in particular, is one of the main interests of this lab that we’ve been a part of. But although we’re going to focus primarily on cognition and birds today and chickadees more specifically, like I said, cognition exists across the animal kingdom, cognitive abilities, even our little inverts like this little bumblebee here have highly advanced cognitive abilities.
And what you’re seeing here is all different examples of cognitive tasks that folks might ask animals to perform in the laboratory. And traditionally, that’s what folks have done. We’ve looked at cognition in the lab, whether or not it’s counting like this chimpanzee is doing here or if it’s something like a spatial task, what this rat is performing here in this circle.
But the amount of ecological relevance really does vary across these different tasks. So we ask animals all kinds of questions, but oftentimes, they’re not ecologically relevant. And by that, just because an animal can do it doesn’t mean that they will do it in nature or that we should expect them to do it.
So when we start thinking about things like natural selection acting on cognitive abilities, we oftentimes think that if there’s variation in a trait so that it differs among individuals, that it must be useful, there must be some resonance that’s there. It must be selected on.
But in reality, we shouldn’t expect organisms or animals to be highly cognitive unless it’s really critical for their survival, or their reproductive output, or fitness as we call it, because the neural structures involved in high cognitive abilities are really expensive. So it’s not free cognition. So just being smarter isn’t always better, being highly cognitive isn’t always a better trait to have. So that’s something that’s fun to think about and take a step back from.
I always say that animals are as smart as they need to be, and I stole that quote from somebody else. So I don’t want to take credit for it. But it’s true. So they’re just as smart as they need to be. So anything that they can’t accomplish doesn’t have anything to do with them being smart or not. They’re able to survive and reproduce in their given environment and that’s the critical thing, critical goal of any species if you want to say there are goals.
So when we move into something like spatial cognition, spatial cognition is particularly relevant because we’re talking about, and I say relevant in terms of ecological relevance. So again, just because an organism can do a task like learn to use a tool or learn to count doesn’t mean it would use that or do that behavior in the wild.
But something like spatial cognition is inherently ecologically relevant, because spatial cognition really is what organisms use to navigate their environment. And that’s whether or not they’re navigating to a food source, a territory, a mate, things of that nature. And so spatial cognition can be really specialized.
So it can be innate. So it could be something that the organism is born with or in their genes. And so we think about that often in terms of seasonal migration. So migration is one of those things that is innate in organisms. They have innate response to migrate during certain seasons based on cues they’re getting from the environment.
And then an alternative strategy, of course, if you don’t migrate when food runs out seasonally, then you might have an alternative strategy which might be food storing or caching food, which again, depending on the type of caching you do, require some level of spatial cognition as well to remember where your locations are.
So the notion of caching food is an innate behavior in the sense that organisms are just, it’s a compulsive thing. They have to do it. And so we were talking about this before we started the webinar, something that’s really cool is that many food caching animals will actually store rocks or non-food items when they are kept in the laboratory even though it’s not food. But they have this compulsion to need to cache.
And this is true as well when you’re thinking about satiation. So they’re in the lab, they have all the food they could ever want and yet they still cache food and store food because it is this innate compulsion they have. That said, when we think about spatial cognition, anytime we’re thinking about cognition, that also is linked with the neural mechanisms or the brain structures associated with it. And for spatial cognition, that’s the hippocampus.
And so we can see here in this little silhouette the hippocampus of humans is inside our brains. So it’s actually in the middle. So this is like a Zoom in of it or a photo that’s showing inside. But what’s really cool about birds is the anatomical structure is right here at the very top of their heads. So it makes it really easy to access for scientists when we do want to look at activation in the brain related to spatial memory. We can access that pretty easily.
So in order to ask questions about spatial memory, we actually have to develop really specific tasks because spatial cognition is very different than other types of associative learning. So you might learn, I choose the stimulus that is read. So I’m given a choice of red and green. I always choose red because red is correct. That’s not a spatial task. That’s an associative learning task.
So if you want to ask an organism if they’re using spatial memory or spatial cognitive abilities, you have to create these apparatuses that don’t have additional traits to them. So all that they’re using to actually locate where a food source might be is where that food source or where that hole is or compartment is within space.
So they might be able to use landmarks like this desk over here to be like, OK, so it was closest to the desk, but a little to the left of it. But there are no other cues here. There’s no color associated with each of these holes, no tactile stimulus, et cetera. So this is often how folks study spatial cognition in the lab. So let’s see. I think we wanted to talk a bit– sorry about that, Sara.
[Sarah Wagner] Yeah, that’s fine. Tell us about caching.
[Carrie Branch] Yeah, so when we think about– of course, I’m talking about spatial memory. But for today’s topic, that’s particularly related to food caching. So again, you can think of food caching as this alternative strategy to migrating. So instead of moving to where your food will be, you can keep the food where it is or where you are and use that throughout the winter. And so that’s exactly what these organisms do.
So they’ll store food items when it’s abundant, so in the fall, to use later throughout the winter when it’s scarce. So they no longer have these seeds available, but they’ve stored a bunch of them elsewhere. And there’s actually a scalar gradient of hoarding behavior. And so we refer to this as scatter hoarding versus larder hoarding. We see here at the top.
And so scatter hoarders are animals, both birds and mammals. So this little gray squirrel is a classic example that actually cache individual food items in different locations. So each seed, each acorn essentially is cached or stored in a different spot. It might be in the ground for things like squirrels and these Scrub Jays. But it might be in trees, or in the bark, or moss for some of our smaller bird species.
And then there’s some of these in-between guys, so a lot of Corvid species, again, not the Scrub Jay, but some of our other Corvid species like Pinyon Jays and Clark’s Nutcrackers, will store a couple of seeds in one location. So it’s not necessarily one individual seed, it might be 5 to 10 in one little location, but they’ll still have multiple spots around their territory where they stored food. And they also go much further distances when it comes to caching their food items.
And then finally, that moves us to the other end, which is larder hoarding, which is where they just store a bunch of pieces of food in one location and then they defend that location. So for birds, a great example is this acorn woodpecker that has this granary. So you can see here all of its little acorns that’s stored, and they’ll sort of defend this tree.
And the same is true for red squirrels, and squirrels in general we often think of them as squirreling things away. So keeping a bunch of things to themselves or hoarding things. So the red squirrel is an example of that classic storing a bunch of food items in one location, often against foxes benefit. So sometimes they’ll store a bunch of food items in like the trunk of a car or the hood of a car rather, and you go and you’re like, why is my car not starting? You open it up and a squirrel has created its mitten or its larder hoard there.
So that’s a bit about– you can think about the trade offs there in terms of if you’re a scatter hoarder, one of the benefits is all of your food is in one place. So if a rival comes along and finds your stash, all of it’s gone. But if you’ve stashed all over your territory, you wouldn’t lose everything. The trade off, of course, is you have to remember where all those different little food stores are, and that creates more selection or more pressure on having these better spatial cognitive abilities that we’re talking about.
[Sarah Wagner] Awesome. I just asked you to give like too mini-lectures. Great coverage of cognition and caching. Thank you so much. I think maybe you have another slide with some pictures of caching in progress.
[Carrie Branch] Yes, here we go. So this is an example of one of our chickadees caching a food item. So Mountain Chickadees are often caching conifer seeds exclusively really except for when we get them sunflower seeds. And so you can see is just placing it in the bark here, and he’s like, hey, don’t be looking here. This is my cache. So yeah, so that’s what it looks like when they will cache a seed.
[Sarah Wagner] Awesome. Yeah, actually was able to see this yesterday just because I saw your previous slide. I was like, oh, I thought it was just using it to manipulate the seed. But anyway– OK, so because a lot of us have been stuck close to home lately, I’m really excited for Ben to tell us more about what the field site is like and also what are some of the spatial tasks that you ask chickadees to perform. So take us there, Ben.
[Ben Sonnenberg] Yeah, so we’ve been studying these birds for a really long time. And we mentioned that there is two elevation sites, one that’s turned our high elevation site, which is about 2,400 meters or like 8,300 feet. And low elevation, which is about 900 meters or like 67, don’t check my math, feet.
And so we found lots of elevation-related differences in variation in a laboratory setting. So it actually started in the lab where we took these birds into the lab. And we found differences between caching behavior, so high elevation cache more food. We found differences in spatial memory abilities, with high elevation birds having better performance on our spatial learning task. And I’ll tell you exactly, in the lab, we measured spatial memory a little bit differently.
And we’re not going to worry about that today. We’re going to focus on how we measure spatial memory in the wild. But we did find differences between birds that we brought into captivity from these high elevation sites and these low elevation sites. And in corresponding, Carrie mentioned that there’s differences even in the neuroanatomy of birds.
And back in the day when folks were actually looking at some of the differences in brain structures in species just across the globe, early neural anatomists made the assumption that if you saw more brain matter associated with one area of the brain, that function might be more important to the natural history of that animal.
And a wonderful examples that most birds have relatively poor senses of smell, for example, and they have teeny-tiny olfactory bulbs in their brain just like we do. We don’t have good ones at all. We have tiny olfactory bulbs in comparison, comparing across species.
But if you look at, say, kiwis, so small terrestrial birds native to New Zealand, which filled the rodent niche and actually run around sniffing for insects, and the tips of their nostrils, their nares is on the tips of their beak as they run around and shuffle, they have massive olfactory bulbs and they have excellent senses of smell.
And there’s other birds too, such as procellariiformes such as seabirds that are aligned, and vulture species that also have large olfactory bulbs. But if you look at kiwis brain, it has huge olfactory bulbs. And for us and chickadees, we found differences in their hippocampus. So the brain region that corresponds to spatial memory, we found larger and more neurons in the hippocampus of high elevation dwelling chickadees compared to lower elevation chickadees.
And so that’s super interesting that we found such differences across such a small spatial scale, because these sites are only six miles apart. We’re not talking about across the United States. We’re not talking about comparing Seattle and Anchorage, Alaska. We’re talking about comparing six miles apart.
But it’s separated by an elevation gradient, which provides a natural experiment, if you will, of comparing to different subpopulations of animals or animals that don’t move very much, that stay on the top at high elevations, and some that stay at the bottom at low elevations, and we can detect some of these differences. Because one of the things that you have to remember, even about these chickadees, is that they’re not flying off to Hawaii during the wintertime, sitting on the beach, kicking back, drinking a mealworm mojito. They’re toughing it out in the wintertime.
And so we at our field site collect data year round. And we know a ton about chickadees. And that’s why the chickadees are just fantastic study organisms because they come to boxes, they’re residents. So they come to our nest boxes that we provide for them in the woods, and we can band those birds, and we can track them year round because they don’t leave. They don’t migrate. They’re around all year round. So we can monitor specific individuals and we can monitor new individuals.
And so in the fall, we band as many birds as we can, and we can take DNA samples to see who’s related to who. In the wintertime, we actually– and that’s what we’re going to be focusing on mainly today– is we collect cognitive data. So in the wintertime, so actually right now, I was just out in the woods yesterday on a snowmobile collecting data and banding chickadees, getting ready for our spatial memory experiments this coming winter. And so that’s going to happen. And we’re mainly going to be focusing on winter stuff.
And then in the spring and the summertime, we collect song, and we collect all sorts of other measurements such as reproductive data, how many eggs are individual females laying? How many babies do they actually fledge? What sorts of things are they feeding their babies? How big are their nests? How many parasites are in their nests? Who’s mating with who? And all sorts of other details. And so we follow these guys around.
The only problem is that, if you’ve ever met a baby chickadee, they’re extremely grumpy and they never appreciate any of our efforts. But we’re working on it, we’re working on it. Bad attitudes, you know.
And so to just give you a flavor of what our field site looks like is we’re a bunch of weirdos, and we have all these crazy machines that help us get to these high elevation sites. When I normally talk to a lot of scientists, they say, well, it’s wintertime now and our field season’s ended. And I say, our next field season has begun! And they say, what do you mean? You can make it to the top of the mountain? And I say, oh, you haven’t seen our tract four-wheeled vehicles.
And so we actually have four-wheel drive vehicles that are equipped with snow tracks that allow us to climb up the mountains and bring equipment to service these feeders. And we do this in all sorts of weather. And so I can’t tell if that video is playing. Yeah, so here is just an example of a nice, wet snowstorm, maybe some of you guys up in the Cascades might be familiar with that. That was a wet, wet day.
And so we’re servicing these feeders. And we also do have snowmobiles in other sites. So you can see the next video has just some of the beautiful sights we see. This is primarily coniferous forest that Mountain Chickadees are living in. And so that’s primarily the forest that we work in. And they have widely spaced trees, and it’s nice and maneuverable. And we’re able to navigate the landscape and get where we need to go during the winter months.
[Sarah Wagner] So Ben, can you just tell us, for example what was the temperature yesterday when you were out.
[Ben Sonnenberg] Well, So growing up, I’m originally from Montana. And so it’s actually much warmer temperatures relatively in the Sierra, Nevada. It rarely gets for example below zero. And so you guys in single digits right now, that’s pretty unusual for the Sierra, Nevada. Cold days and cold temperatures are like probably low 20s, high teens. And so yesterday, it started out in the low 20s, but then probably at the end of the day was and mid 30s.
[Sarah Wagner] OK.
[Ben Sonnenberg] Yeah, so we’re not too cold anyway. But there’s lots of snow. And this last December actually, we set a record. We broke the record for most snowfall in the month of December ever, and the last record was sent back in the 1930s and we got eight feet of snow or something like that.
So then this leads me to how we actually measure behavior in the wild. So measuring behavior in the lab like Carrie alluded to, it’s interesting and it’s nice. But there’s all sorts of problems with the lab, because we don’t know if animals are actually behaving as they would when they’re out in the woods, because they don’t have the woods. They don’t have all these trees. They don’t have this landscape. They don’t have all these things to navigate. So are they actually, all these things that we saw in the lab, all the differences in their brain, regions, and their behavior, is that true, does that stay put in the wild?
And so Vladimir put together this amazing design of basically an array of feeders that allows us to test birds spatial memory abilities and performance in the wild. And so that’s what this looks like right here and that hanging group of feeders. And you might ask why are feeders are– so it’s absolutely ridiculous. They hang sometimes like 25 feet in the air. And sometimes it’s snow related. But actually in the beginning, it wasn’t at all snow related.
I don’t know if anybody has had this experience. We were not trying to test the cognitive abilities such as problem solving of the black bears of the Sierra, Nevada, but we sure by golly did by accident. This mother black bear really tore apart the original design of the feeders that we were all going to have them on poles. And you can see that she’s such a strong bear.
She alluded an electric fence. She bent these big steel poles. You can see the little cubs over there playing on a bed of nails. I think they were trying to exfoliate their foot pads, even at a young age, it’s important for pad health. But they didn’t care at all. And so we had to actually hoist all of our feeders way up into the trees so that we could work with them. So that’s why they’re hanging in the trees.
But what our individual feeders within a spatial array look like is that they’re actually equipped with what’s called Radio Frequency Identification or RFID technology. And that allows us to detect and monitor individual animal behavior, because chickadees, is like what Carrie just circled, are banded with individual PIT tags, so that big white tag on that bird in the hand. And that tag has an individual ID associated with it.
And when the bird comes in and lands on that feeder, that black perch that it’s landing on is actually an antenna, and that antenna scans the pet tag and allows the door to open for that bird so they can get a seed, but it scans and records the time of day, the individual, and even sometimes how long it was sitting on the perch. But that allows us to monitor who’s coming and who’s taking seeds from our feeders. And all of them are associated with these 10-digit numbers.
And you guys actually might be familiar with PIT tags, just the general public, because a lot of people have PIT tags in their pets. So if you have a PIT tag in your dog’s neck, they all correspond to a unique code of that individual animal. So you can track down fluffy when fluffy runs off. And in our case, all of our chickadees are 10-digit bands. And my favorite being 0700EDBA17. And I was told at the end, there will be a quiz. So just retain that.
And so we’re able to record all of that information. And I actually have some examples too just in my hands here just so you can see how relatively big it is. But these are microcontroller boards, either made by Arduino or hand-built, and that’s what actually is inside the feeder operating the door. So that big silver cylinder is actually a little motor and then there’s some gears in there and switches that all operate, that actually allows that microcontroller board to scan, store the data, and open and close our feeder doors and allows us to test birds.
And so what testing actually looks like is that first, we have to get the birds just used to the feeders, because feeders opening and closing doors are scary. And so any bird that comes to the feeder that has a PIT tag, all the doors are closed, but all the doors will open for the chickadees at first. So all eight feeders open and allow a chickadee to have a food reward.
But then when we’re actually ready to have a cognitive test, when we’re ready to test the memory abilities, we only assign a single bird to a single feeder in the array of eight years and then we see how well that bird learns that location. And what that looks like is when a bird comes in, remember, all the feeders were rewarded. And so he goes to sample some of the feeders that we’re giving him seeds, oh, he doesn’t get a seed from his first try. So he goes and samples some more and still doesn’t find any seeds.
And so then he finally finds his rewarding feeder in that spatial location. Yeah, you got a seed. So he might fly off with that seed, he might eat it, he might catch it. But then what’s really critical is what happens next. And so when he comes back to the feeder, oh, he immediately went to the feeder that was rewarding. And so then that’s a sign that he learned something.
And so this is actually how we’re able to measure learning. And so in a first trial, a bird might make three errors before finding the correct feeder, might make two errors in the second trial, but then never make an error again in subsequent trials. And if you can imagine, that’s a learning curve. That’s improvement over time.
And we’re able to assign individual metrics, so how fast an individual learns and then retains memories of a spatial location using these feeders, so each individual bird participating in the wild as they’re self-motivatingly coming to these feeders, and allows us to measure this behavior in the wild, which is just absolutely incredible. And actually watching these birds interact with our feeders is just, it makes my jaw drop every time.
[Sarah Wagner] That’s the way you want it to be. That’s awesome. What an elegant design. Ben, I’m going to give you a break for a minute and ask Carrie a question before we switch gears and take audience questions. So Carrie, it’s a pretty big deal that you’ve been able to show that genetic differences underlie natural individual variation of spatial cognitive abilities in this wild population of birds. Could you unpack that for us a bit?
[Carrie Branch] Yeah, absolutely. So we’re talking a lot about spatial memory abilities and about differences in these environments. And the take home there is that the selection pressures at high and low elevations differ. So it’s much harsher at high elevation. So if you wake up in the morning and don’t know where your food store is, it’s curtains. So it really is life or death for these birds to be able to remember those food stores, where they are, and to make sure that they recall those locations. And that pressure is much stronger as our high elevation.
And what we’ve actually shown through using a cohort comparison, so actually Ben made this beautiful slide for us with the little silly hats on all of our little first year birds, for example. You can think about this about, he makes the parallel to whether or not they would graduate. And so these individuals are there and they’re maybe at their freshman year. By the time graduation comes around or, for our sake, one winter, over that winter, some will graduate or survive and others won’t graduate or will die.
And so those individuals that survive actually have better spatial memory abilities compared to those that don’t survive. So we’ve shown this in our population. And from that, that’s one aspect of selection, showing the selection is acting on spatial cognitive abilities. But what we were really interested in is whether or not there’s a genetic basis for this trait and whether or not they’re able to pass it on to their offspring.
And so very recently, we just published this, actually today it’s coming out in print, which is really exciting, this work about the genetic basis of spatial cognition in current biology. So this is actually our graphical abstract. So you’ll recognize this if you look for the paper. And essentially what I’m showing here is individuals perform a certain way on our task.
And what we looked at is that individuals that make few errors, so this guy only made I error or he made zero errors rather, compared to an individual that might make two errors before going to its correct feeder. So by taking those individuals and comparing their genomes and where they differ in their genomes, so an individual that maybe makes few errors compared to one that makes a lot of errors, we look at where they differ in the genome.
And what we see is in these instances where they differ, the genes associated with those genetic regions are actually related to neuron growth and development, as well as hippocampal function. And a lot of these genes are actually described in humans since that’s a lot of where the work is taking place, especially for medical reasons.
But what we’re showing is that these individuals that perform better or worse on our task, there’s a genetic basis for this. They do differ genetically, and it is related to things we’ve seen before, which is differences in spatial cognition or hippocampal function which controls spatial cognition.
So this is really exciting. And one of the first times it’s been shown in a bird species actually. So we know a bit about it in humans and a bit about it and lab mice and rats. But we’ve never seen it in birds before, although it’s been long hypothesized that this is what’s going on in these bird species. So it’s pretty exciting stuff.
[Sarah Wagner] Very exciting, and congratulations on the paper.
[Carrie Branch] Thanks.
[Sarah Wagner] All right so we are going to switch gears and take audience questions for the next few minutes that we have left. OK, so let’s see what we’ve got here. Here’s a question that I’ve seen a few times from the audience just about the spatial and temporal patterns of caching. So what period of the day, or the season, or I guess, the life history are birds caching? Do they know how– at what age did they start exhibiting caching behavior? And then what are the patterns within a day?
[Ben Sonnenberg] I can take that one.
[Sarah Wagner] Sure.
[Ben Sonnenberg] Yeah, so we know a little bit more about how it develops in jay species, but they’re probably very comparable in that birds start caching when they’re extremely young. And it’s actually been shown that they start caching before they develop the ability to even recover the cache. So young birds will just be like, oh, wow, I need to hide this. And that’s been shown in California Scrub Jays, for example.
And so it likely develops very early, because there is a strong innate drive to go cache. And so the caching ability develops pretty early, but then probably the associated ability to go recover those caches develops a little bit later. And birds primarily cache really heavily just when resources are available.
So in our Sierra, Nevada, for example, we’re talking about– it’s dependent on the pine species. So Western white pine, mountain hemlock species, when they’re actually producing cones and those cones that are producing pine nuts, when those pine nuts are available are when the chickadees are catching the very, very most. And so that’s in the fall or early fall to late fall and even into the winter months.
But one of the amazing things about chickadees is that if you give them food to cache, they’ll cache it. And so if you watch your birds coming to your feeders very closely, Black-capped even from Maine to these all over the East Coast, even off to the West, my mom’s bird feeder in Montana.
If you watch them closely, sometimes you can see a bird come to the feeder, grab a seed, and then fly up to a branch and they’ll eat it. But sometimes you can watch them eat it, but sometimes they’ll just disappear, and that means that they probably wouldn’t cache that seed. And so if there is food to cache, they’ll cache it on, which is a very interesting component of that behavior. But it’s a really strong drive to cache.
[Sarah Wagner] Cool. OK, are there any similar cognitive studies with Black-capped Chickadees in the Northeast? is a question.
[Carrie Branch] Yeah, so Black-caps were the basis of the original work looking at differences within a species. So for a long time, folks were studying differences between catching species and non-caching species. And Vladimir came along and said, I think it’s the environment that’s shaping this. I think we should look within the same species, but across a gradient of winter harshness.
So Black-caps are great for that. As we discussed, they’ve got this huge geographic range. So you can look at them from Maine to Missouri to Alaska to Washington, all the way up to Fairbanks, Alaska. And so while it wasn’t focused primarily in the Northeast that study looked at variation. And what you see is it’s not about just the latitude, so just because it’s an increase in latitude doesn’t mean that the birds are performing better on that spatial task and have larger brains. It’s actually the environment.
So birds in Washington have pretty terrible spatial memory despite the fact that they’re quite far North, but they’re live in the lap of luxury up there. So it’s like more of a Mediterranean climate. So they actually have relatively small brain regions and abilities. But there is a good amount of work.
So Bob Curry is a scientist who focuses on Black-capped Chickadees and hybridization of Black-caps and Carolinas, is along with the folks at Lehigh University where they’re looking into cognitive breakdown in hybrid species, because we do know that their fitness is lower and there’s a little bit of evidence that they perform worse on spatial cognitive tasks.
So yes, there’s lots of work on these topics. The interesting thing is folks are trying to replicate the study system, but it’s really difficult. And even when they’re not working in a really harsh montane situation, they’re still having a hard time actually getting the data. So we feel really fortunate to be part of a team that’s actually been able to accomplish this and to get this data. It’s really difficult to gather this data. So–
[Sarah Wagner] Yeah, I imagine. This one might be kind of hard to answer. This one is from Facebook. How likely is it that other birds will find their caches and steal from chickadees?
[Ben Sonnenberg] Well, so if you want a likelihood, if you want a number, we don’t have the answer to that. However, Mountain Chickadees do travel in mixed flocks as do Black-capped Chickadees. And sometimes they travel with other caching species like nuthatches, so White-breasted and Red-breasted Nuthatches. And there is absolutely pilfering that happens.
If another caching species is just searching a tree and happens to find a cache, they will absolutely pilfer caches that are made. And so there is that, that happens. We don’t really have a grasp on how much it has happened. However, when we’re talking about caching done by Mountain Chickadees, we know that they cache tens of thousands of individual food items. And so a few going missing here and there doesn’t really affect their overall chances.
[Carrie Branch] Yeah, and that really does go back to thinking about different hoarding strategies, the difference between scatter hoarding, if you lose a couple, it’s no big deal, versus if you put all of your eggs in one basket, so to speak, then you really have to protect that hoard because if it’s gone, that’s your whole survival for the winter.
[Sarah Wagner] Right. OK, this is– we’ll just do one more. And this one you might be able to answer because you do have individuals banded, but we’re seeing a few questions about individuals moving up and down in elevation. So can an individual who has fledged in a higher elevation move to a lower elevation to survive due to its lower ability to find caches?
[Carrie Branch] Yeah, so that’s a really great question and the basis of a lot of what we did originally and we’re trying to convince those before we could bring things into the wild that selection was acting on these birds and on the spatial memory ability, like, no way, it’s got to be plastic. They could move up from low to high and then just learn how to be better at the task over time.
But what we find is that it’s really not that plastic. So we’ve already talked a bit about the genetic basis, which again this does not mean the environment is not important. It absolutely is. But it does lay the foundation, apparently, for how well they’re able to perform on these tasks. And we do know that they move between elevations.
As we know, there’s the level of gene flow, which just means that if you want to think of high as one population and low as another population, they’re not true populations because there’s gene flow between them. But these are resident birds and they don’t move very far, and then they stay there for the rest of their lives.
So we’ve never truly documented an individual that was hatched at low reproducing at high or vice versa. And we’ve done some more research on this as well, looking at social dynamics and dominance because dominance is so important for these flocking species. So what we see is that if a low elevation bird were to move to high, likely wouldn’t survive because they have the poor spatial memory abilities.
But then if a high elevation bird is like, well, why don’t they just drop down to low? But we’ve actually shown that they’re socially subordinate to our low elevation birds. And so that would have ramifications for their fitness outcomes, because more dominant individuals get better access to food, better access to mates. And so it does seem like they’re separated based on these behavioral traits
[Sarah Wagner] Yeah, oh, wow, that’s super cool. Great questions, audience. Thank you so much. We have so many questions. We just answered a few. But definitely feel free to reach out to us later for those– hopefully answers and hopefully you got a lot of great resources from our team behind the scenes.
I’m super sad that this is coming to an end. It’s so nice to see everyone and to chat about your research. And I’m so impressed with you both. Carrie and Ben, thank you for taking the time to talk with us today and sharing all of your great research and your wonderful ability to share that and to teach us. And thanks also for all of our behind-the-scenes help. We have Leo, Katherine, and Chelsea helping us out today.
Tomorrow I’ll be emailing Zoom attendees with a recording of the webinar and all the resources, well, some of the resources that we’ve discussed and have been handed out today. If you’re watching on Facebook, check the comments for links and resources. This webinar is part of a series. We’ve been spotlighting programs and research from around the Cornell Lab.
This work, including today’s webinar, is funded primarily by people like you who choose to become a member. If you enjoyed today’s webinar, I hope you’ll consider becoming a member too by visiting birds.cornell.edu. That’s all for today. Thanks again to our panelists and for this wonderful audience. Have a great afternoon and maybe get some sun, or snow, or whatever you can get wherever you are, just get outside maybe. Thank you so much.
[Carrie Branch] Thank you so much for having us. It was really fun.
[Ben Sonnenberg] Yeah, thank you. Go spot a chickadee, everyone.
[Sarah Wagner] Yeah.End of transcript
Every fall, chickadees hide tens of thousands of food items, counting on these “cached” seeds and even insects to see them through harsh winters, deep snow, and subzero temperatures. But how does a tiny bird weighing only half an ounce remember where they’ve stashed all their food? Join our conversation with researchers Dr. Carrie Branch and Benjamin Sonnenberg as they reveal how Mountain Chickadees make it through to springtime with the help of cached food, enviable memory skills, and some surprises when it comes to choosing mates and building nests. We’ll also spend time answering your questions about these energetic birds during a live Q&A.