Scott Taylor: I've woken up in a lot of different places. My childhood home in Inverhuron, Canada, where black-throated green warblers and American redstarts are the official sound of late spring. A rented apartment in Ithaca, where tufted titmice and northern cardinals carried me through gray winters and lush green summers. And the house I live in now in Denver, where northern flickers and black-capped chickadees seemingly conspire with my dog to get me out of bed every morning. Different locations, different views, but always the same thing. Coming through the glass first birds and listening to them has always been how I know where I am. That flood of morning sound has a name, the dawn chorus. It's almost entirely layers and layers of bird songs, not calls. Songs and calls are two different kinds of bird sound, both important but for different reasons. Song is their performance, it's the long, structured, showy stuff, and it's doing 2 jobs at once, helping birds hold territory and attract mates like this. In general, birds sing just before and during the time of year that they reproduce, spring and summer in the northern hemisphere, but often year round in the tropics. Think about when you first hear chickadees singing in the spring. Calls, on the other hand, are shorter, plainer, and more functional. They can happen at any time of year. They're the everyday messages, like, oh, food, or there's danger like this. So that wall of sound outside your window in the morning? That's the dawn chorus of birdsong. Whole communities of local birds advertising their territories and trying to get the equivalent of a swipe right. But lately it's gotten, well, thinner. Which brings us to the topic of today's episode. Okay, but is the dawn chorus getting quieter? To help us unpack that, I'm joined by Dr. Dan Mennill, a professor at the University of Windsor who studies whole neighborhoods of birds at once. After the break, Dan explains what all that morning noise is actually for. We get into what he heard when he wired a forest with microphones, and he tells us about a field site that recently went shockingly quiet. Stay tuned.

Scott Taylor: Well, welcome back to the podcast, everyone. I'm really excited to have Dan with us today. Thanks for joining us, Dan.

Dan Mennill: It's a pleasure to be here. I'm a big fan.

Scott Taylor: Well, that's always nice to hear. I thought that we could just start off with a broad question about, you know, why do birds sing in the morning? I think it's a thing a lot of us have noticed, or maybe not. Why does it happen? What's it conveying?

Dan Mennill: It's a great place to start, and there's kind of two questions hidden behind your question of why do birds sing at all? And then why do they do it so much in the morning? I think we should start with the why do they sing at all? And birdsong. We know it to be a a two-function signal. Birds sing to achieve 2 things. The first is to defend their territory their their breeding resources from intrusion by other same sex would be intruders. And the other reason is to attract members of the opposite sex. And for some people who haven't thought about this before, birdsong isn't like human language. It's not like different notes that symbolize different ideas. Instead, birdsong is something that induces changes in the other birds who hear it. It is a persuasive sound, not a symbolic sound. And so, you know, that first function is kind of like whenever the the Hulk screams, he sets up sort of an invisible force field around him that prevents intrusion. That's the first part. And then the other part is like a a talented street musician who as they play it attracts people. And so it's those two things happening all at once, defending and attracting with that one common thing that we call birdsong. And you know, and everybody knows humans have known for a long time that the time you're going to hear birdsong most likely is early in the morning, especially around dawn. If you're an early riser, you love the dawn chorus this time where all the birds wake up and start to sing, multiple species, all singing and filling the airwaves at the same time. And if you like to sleep in, maybe you curse the dawn chorus. Depends on how close it's happening to your window I guess, but yes. But it is something that is commonplace in diverse bird species to sing, especially at dawn. It's been part of human culture for the longest time. Ever since we domesticated chickens, we've had roosters crowing to bark the announcement of dawn. And the dawn chorus is especially well known in their smallest birds, the songbirds, who are, you know, the most biodiverse group of birds and the most common participants in the dawn chorus.

Scott Taylor: Yeah, that's so funny. I've never thought about roosters as being part of the dawn chorus, but you're entirely correct, Dan. OK, so why dawn then? I guess, you know, it is this thing we notice probably if we're trying to sleep in. We hear that, you know, birds are quite loud in the morning. But what is it about dawn specifically? That is the time that all these birds are making all this noise.

Dan Mennill: Dawn is the perfect time to belt out a long bout of song for multiple reasons. One is atmospheric. There's usually very little wind at dawn. The temperature is slightly lower. These are ideal conditions for getting your voice to travel a long distance and reach as many ears as possible. It's also an inefficient time to go out foraging. You can't see very well, and if you're going to be out there looking for insects in those cooler temperatures, the insects are not going to be very active. And it's a time where most predators, many visually oriented predators, are not going to be as great a threat to you. If you sit on a branch and broadcast your location through the proclamations of a beautiful song, that could attract a predator at other times of day. But at dawn, it's not as likely to attract a predator, and so it's a safer time in addition to being atmospherically stable and inefficient for foraging.

Scott Taylor: Totally. Yeah, lots more reasons, I guess, than I was even thinking about for why it would make sense. I I had thought about the atmospheric peace, but not necessarily like the accessibility of insects. But you're right. If you go out in the early morning, there's often all those insects still perched, covered in dew, waiting, waiting to get warm enough to fly.

Dan Mennill: Yeah, or if you're in the tropics, you're the lizards you intend to eat are not going to be out and about scuttling at that time of day. Yeah. I mean, ornithologists have been trying to figure out the mechanics of the dawn chorus for decades and decades. And some of those earliest ideas were about how the environment impacts the bird's voice. And how the daily budget of activities means that the dawn, and to a lesser degree the dusk, could be an ideal period to announce that this is your territory and perhaps to attract mates as well.

Scott Taylor: What's actually happening, You know, during the dawn chorus? Is there an order of who sings first, who comes in later? And we've talked a little bit about why so many birds pile into that kind of pre-sunrise window. But what? What is the function of all of this?

Dan Mennill: Yeah, ornithologists have talked about the functions of the dawn chorus for so many years. They've talked about those environmental features that we spoke about. They've talked about the circadian rhythms that govern all organisms, that drive them to exhibit particular behaviors at particular times of day. But it's those social functions that are really interesting to me as someone who studies bird behavior. Those social functions are really important at dawn. These birds are communicating with other animals around them. They are well in the temperate zone. It's especially the vocalizations of males. There is a historic male bias in people who study birdsong, and we have a lot of work to do to try to better understand the voices of females. Nevertheless, it is true that in the North temperate zone, you really have a lot of the males that are vocalizing in particular at dawn. And I think what the dawn chorus is, is an interactive network of all sorts of males interested in defending their territory and attracting mates. And they're all piling on to do it at the same time. And there's some really wild effects.

Scott Taylor: Like, have you ever noticed that a particular species of birds join the chorus in a particular order?

Dan Mennill: Yeah, this is a well documented phenomenon in all sorts of different communities of birds around the globe. We've done studies in our region of Canada that find an alder flycatcher is the first to join the chorus and then a couple of sparrows, the song sparrow, the white-throated sparrow, then the American robin joins in. The others are still going later, the black-capped chickadee joins in and, and if you went out and listened to them on one day and the next day and the day after, you'd find it's that same order of entry into the chorus. So there's some of these interesting patterns like this to the chorus and how the community comes together to produce this soundscape. There's been some work about how important it is for order of entry into the chorus in terms of how big their eyes are. You can actually predict what order birds will enter the chorus by their relative eye size. Birds with relatively large eyes enter earlier and relatively small eyes later. So it may be an issue of how early can you see to engage in any activity at all.

Scott Taylor: Yeah, that's really cool.

Dan Mennill: So how early can you actually navigate a forest, get to where you want to sing from and then start singing is related to relative eye size.

Scott Taylor: That's I wonder then how like the lunar cycles and things like that influence whether there's any variation in dawn chorus, if that like gives smaller eyed birds a chance to start earlier, if that would even be good for them, or if it just be weird for the ones listening.

Dan Mennill: We've looked at at lunar cycle a little bit with the student in Adriana Bruni and my collaborator Jen Foote. We recorded the dawn chorus in Northern Ontario over a long period, including multiple lunar cycles. And we found the entire community moves their chorus earlier if it's a bright moon, a third quarter moon or a full moon. And then if it's a cloudy morning, they'll move it later even if the moon is full. So you can imagine there's many factors that would influence how much light you can see as a little alder flycatcher in a northern forest, and each one of those impacts the timing with which they enter the chorus. But it appears that in this study at least, all of the species appear to be equivalently impacted by bright things such as the moon, or dulling things such as cloud cover.

Scott Taylor: That makes sense, I guess. Yeah, if you have big eyes, you should also be able to see better if it's bright with the moon. So it's really cool that the order kind of stays the same.

Dan Mennill: There's an interesting effect too in the tropics of birds that live in the upper canopy get more light sooner than birds in the middle canopy and sooner than birds in the understory. And guess who sings first? It's the birds in the upper areas and then the midstory, and then the understory making a predictable order of entry into the chorus in tropical environments.

Scott Taylor: It's interesting to think that about how that might influence songs themselves. If you're entering the chorus at a certain time, does it make sense for your song to be a certain way, frequency, amplitude, whatever, so that it can still like be a new thing among the chorus that exists because you've got you got to be able to be heard, right?

Dan Mennill: I've had a few research sabbaticals in France. I've been so lucky to go and collaborate with people there. And if you go in the morning to a market in, in Europe, you can hear, you know, the vegetable vendor and the, the cheese vendor vendors and the fish vendors, and they're all calling out to try and get you to come to their shop to buy their thing. And there's a kind of competition that takes place trying to get the ears of your desired customer to come to your stand. And I think the dawn chorus is analogous to that. We talk about the idea of partitioning the airwaves. The an ornithologist would call it the acoustic niche partitioning, where certain species maybe trying to fit into the sweet spot where your sound could be heard above the cacophony of other sounds produced by other birds or produced by environmental sounds.

Scott Taylor: Yeah, you can't just be heard everywhere. And that could be because there's all these other natural sounds like other birds singing with various frequencies and amplitudes and so on. So in terms of studying the dawn chorus, then it is this, this network of things happening. And you could choose to study individual species, but you've been studying the dawn chorus by recording whole soundscapes, so not just individual birds or individual species. And it'd be really cool to hear how that works and what changes in terms of what we understand when you scale it up from just those single species or single individual studies to this whole soundscape approach.

Dan Mennill: A lot of our research into bird singing involves us chasing 1 bird around with a microphone to try and record its voice. But early in my career I had the idea that we should use multiple microphone systems to record a much broader area all at once. Because if we're talking about trying to study an entire network of communicating animals, it would be really nice to be able to have multiple microphones throughout the forest and record every bird all at once. So working again with my collaborator Jen Foote and Laurene Ratcliffe and Lauren Fitzsimmons, a student, we set up an array of 16 microphones connected with kilometers of cable back to 1 central recording device so that we could record an entire neighborhood of dawn chorusing animals all at once. And our goal was to try to understand better what kinds of social interactions are taking place in that dawn chorus, to really ask the question, is it just a whole bunch of animals belting it out, or are they listening to one another? And changing their own behavior based on what they hear from their neighbors.

Dan Mennill: And when we set up this system, which was tremendously challenging to string kilometers of cable through the forest, it looked like a Maple sugary by the time the whole thing was set up. But it gave us this really special picture in in particular, we were focusing in on black-capped chickadees. Excellent species to focus on. And their their two-note fee-bee song. And what we found is that males will change the pitch of that song based on the pitch of the other males near to them. We found in particular that birds who weren't from a common winter flock but were within earshot of one another would match each other in pitch more frequently. They were essentially using their songs and the pitch of their songs to negotiate their social interactions with the other animals around them. And this created a very interesting effect at the level of the landscape where particular pitches would light up and be common currency among males who were near to each other. And then that would die down. And then in other locations, different birds would be communicating with different pitches, all of it teaching us that birds are using subtle differences in their songs in order to communicate about their social interactions. That probably has consequences in how they interact with one another as the day goes on and as the breeding season goes on.

Scott Taylor: I mean, it's so cool that it was individuals that weren't sharing the same flock that didn't know each other, right? Like individuals in the same flock have a dominance hierarchy. They're aware. Like I'm not going to mess with that guy because he's the one that would kick my butt. But if you don't know that and you're just like pitch matching and kind of negotiating that way, that's that's super cool to think about.

Dan Mennill: And even among the males who were from different flocks the previous winter, they're more likely to do this stuff. Scott, if they were equally matched, if it was the middle guy from this flock and the middle guy from this flock, well, they would do even more of this behavior. As though it's not even just unfamiliarity, but it's unfamiliarity mixed with their relative social status. And those are the guys who are really sorting out their territory boundaries and their relative levels of aggression.

Scott Taylor: When you placed the recorders originally, did you map the territories of the chickadees first, or did you just wait to see how where your 16 recorders were eventually correlated with where those territorial borders set up? Because I mean, ideally you have them at the edges of territories, but territories shift and change in size depending on the species.

Dan Mennill: I would like to impress you by telling you that we very carefully mapped everything and then chose the perfect location for the microphone. On that SO. The truth of the matter is we're uncoiling a 50 meter cable. We reached the end. Well, that's where this microphone's going.

Scott Taylor: Yeah, that's what I figured, but.

Dan Mennill: Later we we started using cordless systems and that's where we could start to impress you, Scott, because there we did in a study of savannah sparrows and how they communicate with each other, we could actually choose to specifically set things up in the ideal location for triangulating the position of multiple birds by setting up at their territory boundaries.

Scott Taylor: I guess then, you know, in thinking about what you've found with the importance of neighbors and the soundscape approach to understanding the dawn chorus and how birds are communicating, we've talked multiple times on the podcast about the fact that birds are significantly declining. You know, since the 1970s, we've lost about 3 billion individual birds in North America alone. Those declines are not restricted to North America. They're happening in Europe and Africa and Asia. Even in places we consider to be, you know, pristine, somehow birds are declining there as well. And So what impact is that having on the dawn chorus? Obviously there's fewer birds just in general, but does the loss of birds from communities have like larger impacts than we might expect on the dawn chorus?

Dan Mennill: One of my favorite studies on this topic is by Wan-chun Liu on chipping sparrows. Chipping sparrows have that great trill. Sort of sounds like a sewing machine or something. And male chipping sparrows love to sing a dawn chorus. Well, Liu did this really interesting thing where he in the middle of springtime chipping sparrows singing their songs. For some males, he trapped all of their neighbors and temporarily removed them. He reintroduced them later, don't worry. But when he removed them, the focal male stopped singing his dawn chorus.

Scott Taylor: Really.

Dan Mennill: Now it's shocking. Maybe it's what you would predict, because we know from many studies that they're socially interacting with each other. Well, if we take everyone else away who is there to talk to, that is really what he found. He also took their females away. In other cases. They didn't stop their dawn chorus. Then they stopped when there weren't other males nearby also singing during the dawn chorus. Therefore, if we have 3 billion fewer birds, and if we have the impact of landscape changes and urbanization as a filter for which species of birds are present, it is likely to change the dawn chorus significantly. It might mean birds do not enter the chorus if they're hearing fewer animals around them. And it might mean that the airwaves are filled with different species, those who can tolerate the anthropogenic influences that we throw at these wild animals. And I think we're just starting to grasp how those effects will play out. The scariest story I can relate to you comes from my study of savannah sparrows. I work with Ryan Norris and Stephanie Doucet and Heather Williams to study a population of savannah sparrows in the Bay of Fundy. They're grassland birds. We know that, like the aerial insectivores, the grassland birds are in big trouble. Their populations are experiencing those steep, steep declines. Our population has been pretty stable. It's been studied for decades and decades by us and researchers before us. But this year, we hit our lowest population size in the history of our study.

Scott Taylor: Really.

Dan Mennill: Yeah. Alarmingly so. Areas that used to be occupied by 345 birds is now just one bird. And his territory is even bigger, extending out into other parts of the population. Now, the. That was alarming. But the part that really freaked me out was when we got to the study site this past breeding season and found they were way quieter. I mean, not per capita. I mean each individual was singing far less than ever before. And I think that that is going to be the impact on our ears is a quieter chorus and quieter daytime song as there are fewer animals around for these individuals to interact with.

Scott Taylor: Yeah. So now there are way fewer individuals. It's much quieter. So this is kind of recapitulating the experimental work on chipping sparrows to an extent that if you don't have a neighbor who's saying anything, why would you speak? It makes me think of how often I talk to myself. If I'm fully home alone, if the dog's there, I talk to him. But in the absence of anything, I'm. I'm quite quiet too. So it does make intuitive sense. But it's interesting to think about the potential impacts that would have on the whole community of birds that are communicating. That's depressing.

Dan Mennill: I'm sorry. It is. And, and I'm afraid it gets worse because we are causing so much more. We're causing so much more noise pollution and light pollution than ever before. And that's another area that we have investigated. How does loud noises of cars and airplanes influence the dawn chorus? How does increasing levels of anthropogenic light influence the dawn chorus? And we know that birds are trying to escape the the busy sound of traffic by adjusting their songs. I've done a recent study of the great tits that live in Paris. Paris is a cool city, period. But Paris is a cool for a lot of reasons. Paris is a cool city, too, because they're fighting noise pollution harder than most other cities. And so I was interested in whether the birds in Paris, who we know, sing up at a higher pitch to avoid that low frequency din of traffic. Might they return down to these lower pitches now that Paris is fighting against noise pollution so hard? But we found that even in spite of a big concerted effort to make Paris just quieter, the great tits are still changed their song, their songs are still higher, and they're not moving back down into their typical singing space. They're still experiencing those negative impacts of noise pollution.

Scott Taylor: What's the time frame on that like in terms of when the great tits in Paris were first recorded singing at this higher frequency? And I will say for folks to you may not like we don't think about anthropogenic noise that much and we because we just like it goes away in our daily life. But if you go outside your house and you live in a city and you just listen for low frequency noise, you're going to hear it. I mean, even where we are in Denver, you hear Interstate 25 when you listen for it, but not if you're not, you know what I mean? Like it's easy for us to just wash those noises out, but they're out there. They're quite loud when you start paying attention to them. Like pay attention to how many jets are flying over your house, those sorts of things. We often have to stop filming this podcast because of jets. And all of that is having impacts on these birds. So I'm curious, like with these great tits, we, you know, the documented increasing in frequency happened then Paris has done all of this amazing work to try to reduce cars, especially in the city center. So what's the time frame of when change happened to what you're looking at now? Like, do you think there's been enough time for a correction, as it were, if it was going to happen?

Dan Mennill: It's a great question and I don't think we know a lot about the onset of this effect. I would imagine the onset of the industrial revolution was noisy and then I had it ramped way up when we all started driving cars and and moving around by planes and having loud industry. So I imagine the crescendo of anthropogenic noise has been near constant. Certainly it was Hans Slabbekoorn 20 years ago who really first documented this effect of traffic noise pushing birds like great tits in the first case, and then many other species. It's been seen in sense up to a higher frequency. Our hope in this recent study was, hey, Paris has been working to reduce this. They've got, they've got little traffic cameras that if you rev your motorcycle, you'll get a ticket. They'll triangulate your position and give you a ticket for a noise violation.

Scott Taylor: I love that my neighbor would get so many tickets and I would love that for us.

Dan Mennill: It would probably interrupt your podcast less often too.

Scott Taylor: Oh my God, whatever.

Dan Mennill: So they're doing that. They've got an electric bus fleet. They experiment with low noise asphalt on their roads so that Interstate, by our way, isn't carrying sound as far. So they're doing so much, they're converting roadways to bicycle lanes and using electric vehicles, which are so much quieter. So I thought, hey, the stage is set. Maybe there is room for those great tits to return to their lower frequency range. But when I revisited the same sites that Hans Slabbekoorn had recorded in 20 years ago, both in down downtown Paris, which is quieter today, and a quiet reference forest outside in an area called Fontainebleau, I found that the city birds are still singing at those higher pitches. They have not returned to the lower pitches that their relatives out in the country are singing at and what we think of as sort of the natural song frequency of that species. So I think the effects are long running and I think they have ongoing effects. Henrik Brumm's research team has done a really interesting thing where they recorded birds in a forest next to an airport and the loud take off sounds, maybe those are some of the loudest sounds that humans make, is a taking off engine. And they found that the loud noise of the airport causes birds to change their dawn chorus by singing earlier in the morning. It's like they need to get their communication done before their sounds are going to be drowned out by the the jet engines. They found that this airport was about to close and so they knew it was about to get quieter, like our work in Paris. They thought, well, maybe this will allow the birds to return to their normal time of dawn singing. But they found that some species did. After the airport closed, some species moved back to their normal dawn time, others didn't. Others continued to sing at the airport, active time of the morning. So the effects of noise pollution aren't something that we can resolve quickly. And they may have long running effects that are going to mean we need to keep studying the dawn chorus, we need to keep fighting noise pollution. Light pollution's a whole other story. But I think the effects could be long running.

Scott Taylor: Yeah, yeah. It's interesting. I think we don't think that way often. Like we think, oh, we'll just solve the problem and then things will go back to normal. And even, yeah, with birdsong, there are learning components, there's obviously evolutionary components, there's mate choice components that are probably all playing a role to prevent birds from just like, oh, we'll go back to what it was because it's changed long enough that that's just not an easy solution. That's really, really interesting to think about. But just in general, I think some people think about anthropogenic noise and this influence of it on wildlife, but not, not that many. Do you know, when I bring it up, people don't. It's, I don't know, maybe habitat loss is an easier thing to conceptualize or something we've all witnessed. Whereas anthropogenic noise is, depending on where you live, maybe not something you think about as much. But regardless of where you live on the planet, there are very few quiet places now. I mean, there's a whole map of quiet, at least the United States. I don't know if they've done it in Canada. And parts of the Mountain West are theoretically quiet. But then if you're over, you know, underneath a jet line, that's not quiet all the time, Right.

Dan Mennill: Yeah. Yeah. There's there's some flickers of hope on this. I'm thinking of a paper led by Elizabeth Derryberry during the the Anthropause when the world did get quieter right after we all started staying home during the COVID lockdowns. And she found that the white-crowned sparrows in San Francisco did react to that quieter environment by singing at more normal pitches. And she also found that they returned to more normal amplitudes. They weren't shouting as much. They were talking in their more normal voice, was the suggestion by her and her collaborators, and that was pretty rapid. That was, hey, we all started staying home and that next spring there was an adjustment. So I think we should take heart when we read a result like that. There is reason to continue on that path to try to minimize our noise pollution because it could be a positive effect. It may not be instantaneous. It worked pretty quickly for the white-crowned sparrows. The great tits teach us that we need to keep working at it and keep our cities quieter will benefit. There's human health benefits. Too. Many being in quieter environments and yeah, you're right, we tune it out, but there's cardiovascular downsides, there's longevity effects of loud noises. So there's good reason for us to fight noise pollution for ourselves and for the birds.

Scott Taylor: All right, we've reached the part of the show we call That's B.S. So that's bird stuff where we give our guests an opportunity to debunk a myth that ruffles their feathers. So Dan, what do you want to call B.S. on?

Dan Mennill: I call B.S. on Hollywood putting the wrong bird songs in movies. I was watching Crouching Tiger, Hidden Dragon. Great movie. It opens at dawn in rural China in the 18th century. A guy leading his horse back to his village and out of the treetops comes the song of a black-capped chickadee. It immediately takes a birder out of the movie. You know Hollywood wouldn't tolerate the sound of a cell phone or a jet engine flying over rural China. And so why do we tolerate the wrong bird songs, especially in a world where so many people care about birds? So my feathers get ruffled when they don't reach out to us ornithologists to choose the right bird songs to go in each movie.

Scott Taylor: I completely agree. I don't think that loons need to be in every spooky forest because they're often not in forests. And, and you're right, you know, birding and bird watching is increasing in popularity. And I feel like Hollywood's going to get called out more and more frequently if they keep using red-tailed hawks for every raptor that's flying around in every movie they ever use.

Dan Mennill: That's an excellent one.

Scott Taylor: Well, thanks so much for joining us on the podcast today. It's been really fun to talk about bird vocalizations and the dawn chorus, and I appreciate you taking the time.

Dan Mennill: What a pleasure. Thanks for the invitation, it was nice to be here.

Scott Taylor: Awesome, thank you.

Scott Taylor: Birds are dinosaurs, and around here we like our snacks. So in each episode of the Dinosaur Nugget, today's Nugget is a quiet Spring isn't just about fewer birds, it's about the one still here, having no one left to sing to. When neighbors disappear, the birds that remain go quiet too, because the song, with no one to answer it, isn't worth the breath. That's a wrap on this week's episode. Okay, but is the dawn chorus getting quieter? Quick ask before you go. We're a small independent show, so a single rating of five stars, obviously, or a follow, does more for us than you'd think. One tap genuinely helps a new listener find us. So if you got something out of this one, leave us a rating or hit follow wherever you're listening. It takes 2 seconds and it makes a real difference. We'll catch you next time. Byeee.

This transcript was generated using AI-assisted transcription and may contain errors or omissions. Please refer to the audio or video episode for the most accurate representation.