The Science of Birds - 5 Awesome Things We Learned About Birds in 2020

Episode Date: December 31, 2020

Despite much of human civilization grinding to a halt in 2020, research on birds continued to be published in scientific journals.Through this research, we learned many new things about our avian friends. In this episode, let’s look at 5 interesting bird studies from 2020. If you want to learn more about them, check out the links below.~~ Leave me a review using Podchaser ~~At the end of the episode, I share a little personal note. :) Happy New Year!A global analysis of song frequency in passerines provides no support for the acoustic adaptation hypothesis but suggests a role for sexual selectionDense sampling of bird diversity increases power of comparative genomicsThe evolution of a tropical biodiversity hotspotPhenological synchronization of seasonal bird migration with vegetation greenness across dietary guildsThe phantom chorus: birdsong boosts human well-being in protected areasLink to this episode on the Science of Birds websiteSupport the show

What do you think 2020 was like for birds? Do you think they noticed that there were a lot fewer humans running around being obnoxious? Maybe it was a good year for birds. They certainly had more of the planet to themselves than usual. For humans, 2020 was, if nothing else, different. I won't repeat the many things that have been said about this crazy year, but I do hope that you got through it okay and that you're feeling optimistic about next year. In many ways, human civilization got shut down in 2020.

But science? Science waits for no one! New research kept being published through 2020. So our understanding of how nature and the universe works kept on expanding, bit by bit, as it has for centuries. We know a lot about birds already. If we didn't, then I wouldn't have much to say to you, and this podcast would be a big waste of everyone's time. But it turns out that there is still so much more to learn about birds.

There's no end in sight. New ornithological discoveries are always on the horizon. So let's talk about some awesome things we discovered about birds in 2020. Hello and welcome. This is the science of birds. I am your host, Ivan Phillips. The Science of Birds podcast is a lighthearted, guided exploration of bird biology for lifelong learners. In this episode, I'll be reviewing five interesting bird studies published in 2020.

I'll provide links to each of these studies in the show notes in case you want to learn more. Also, stick around to the end of the episode, because I'm going to include a little personal note to let you know how things are going. All righty then, let's get into the science. Before we get to the top five bird studies, I want to talk real quick about the bird species that were discovered in 2020. Usually five or six new bird species are described every year. Many of these come from so-called splits of previously known species. For example, evidence from genetic data might compel researchers to divide a single warbler species

into two species. Tadda! New species! This is more or less the way that some new South American species were discovered in 2020. Genetic data combined with geography and to be able to. behavior were used to describe six new ant pitta species from the cloud forests of the Andes. Ant pittas are birds in the family Gralariadi. Similarly, three new Tapakulo species were identified in the Andes of Peru. Topakoulos are in the family rhino cryptidi.

But one study made headlines when it reported five new bird species that were discovered on some small islands near Sulawesi in Southeast Asia. There's a new fantail, a myzumela, a couple leaf warblers, and a grasshopper warbler. These species are entirely new to science. They aren't the result of any taxonomic splitting based on DNA. Ornithologists went on a good old expedition to some tropical islands and they found new birds. This sort of thing happened all the time in the 1800s, but it's very rare these days. So there you go. 14 new birds that no one knew existed before 2020. Hooray for more birds. Okay, let's get into the top five awesome discoveries about birds in 2020. These are in no particular order, so this isn't a countdown or anything. And there were many other

cool discoveries about birds this year. This definitely isn't a comprehensive review. Right now, I'm just presenting some significant studies that I think are super interesting. I hope you will, too. The first study has to do with bird songs and their acoustic properties. It was published in the journal Ecology Letters. The researchers, based in Germany and the Czech Republic, analyzed recordings of singing birds from around the world. They wanted to do. They wanted to test several hypotheses about why birds sing at certain frequencies, as in high frequency versus low frequency. For the last 50 years or so, one of the leading explanations for song frequency variation has been the acoustic adaptation hypothesis. The idea here is that because

high frequency sounds get absorbed and scattered in dense habitats like forests, birds in those habitats tend to sing at lower frequencies. If forest birds want to hear each other, they need to use lower frequencies to cut through all those pesky leaves and branches. Seems reasonable, right? But does reality support this hypothesis? Maybe there are other explanations. For example, body size should also have a strong effect on what frequencies a bird can use. Small birds have tiny sound-producing organs, and this anatomy constrains them. They can sing only at higher frequencies. The syrinx is the structure in birds that makes vocal sounds,

similar to the way the human larynx produces our voices. Larger birds have larger syrinxes, so they can hit those sexy low notes. The researchers collected song recordings from 5,085-85 bird-speople. species from within the order Paceriformes. Paceriform birds, who we often call passerines, are the songbirds. This data set of 5,085 species represents 85% of all songbirds in the world, and about 50% of all bird species. That's a pretty serious mountain of data.

The variable of interest here, or the response variable in more sciencey terms, was peak song frequency for a given species. This is the loudest frequency in the birds' song. The researchers included several other explanatory variables to see if any of them are correlated with peak song frequency. For example, they used a measure of habitat vegetation density for the location of each song recording. That way, the researchers could test the acoustic adaptation hypothesis. The main result of this study was surprising. The data and the analyses did not support the acoustic adaptation hypothesis. I know, right? I was all like, what?

It turned out there was no statistical correlation between song frequency and habitat vegetation density. So, at least based on this study, it looks like birds in four, don't generally sing at lower frequencies than birds living in more open habitats like grasslands or deserts. So this is an example of new research forcing us to change our understanding of a biological phenomenon, like birdsongs. No matter how logical and scientifically grounded the acoustic adaptation hypothesis might be, it's only a hypothesis.

We may need to give it up if a careful analysis with tons of data just doesn't support it. But other researchers may push back and claim that the case isn't closed, that this hypothesis is worth further research. That's how science works, right? So what if biologists still don't find evidence supporting the acoustic adaptation hypothesis after more research? Well, then we might finally have to kick it to the curb and then update our ornithology textbooks accordingly. The second study on our list has to do with genetics and the genomes of birds. This study represents a big leap forward in the amount of genomic data available for birds. The genome is an organism's complete blueprint.

It's all the information needed to build an organism from a bazillion little proteins and other building blocks. A genome is the instruction manual for how an organism grows, survives, reproduces, etc. DNA molecules that make up the genome are what store this vast amount of information. Biologists can use information coded in the genome to learn many, many things about an individual organism. And they can learn even more by comparing multiple genomes across individuals, species, or other taxonomic groups. So the genome is one of the most amazing and rich sources of data we can get, from an organism. In some ways, it's the holy grail of biological information.

You and I happen to be living through a scientific revolution where it's become relatively easy and cheap to sequence the whole genome of pretty much any organism. Until pretty recently, this process would take a long time and could cost millions of dollars. But now, the cost of sequencing the genome of an individual bird or hamster or lobster or lungfish, whatever, is almost down to what you might spend on a couple loaves of bread and some mustard at Whole Foods Market, so about a hundred bucks. The study we're talking about today was published in the journal Nature, so you know this is a big deal if it got into that high and mighty journal. The team of researchers, most of them in Denmark, sequenced the genomes of a

whopping 267 bird species. Combined with what had been done in previous studies, this brings the total to 363. So now there's genomic data available for 363 bird species. This is an enormous accomplishment. Importantly, this isn't just a random selection of species. They were chosen as representatives from across the world's bird families. families like the hummingbird family, stork family, Kingfisher family, and so on. With this recent study, we now have genomes from species across 218 families,

which is over 90% of all bird families. This study was part of a larger collaborative initiative called B10K, not to be confused with Y2K. Remember that? 20 years ago, Y2K? B10K is short for bird 10,000 genomes. If you listen to my episode on bird biodiversity, episode 3, you may recall that there are about 10,000 bird species on Earth. There are more than that, actually,

but 10,000 is such a nice round number, and it's not too far from the truth. This B10K project has the goal of sequencing the genome for every bird species in the world. That's pretty ambitious and pretty awesome. And actually, it's well within the realm of possibility. With this recent study, we're talking about the B10K project hit a milestone by getting genomes from most of the bird families of the world.

This study made available a wealth of new and incredibly useful genetic data from across the avian tree of life. Over the coming years, this publicly available data will probably help biologists answer big questions about things like the evolution of birds, their physiology, their behavior, and more. Our third cool study from 2020 looked at how the environment influences bird species diversity. Specifically, it addresses the age-old question of why biodiversity is so much much higher in the tropics than almost everywhere else on earth.

We all know that there are more species of just about everything in the tropics. More bugs, more frogs, more nightmarish parasites that burrow into human flesh, and, of course, more birds. Birds reach their highest diversity in the New World tropics of Central and South America. The study I'm talking about was published in the journal Science. That's another top-tier publication, like the journal Nature. This study was the effort of a large team of researchers from many countries. They collected and analyzed a bunch of genetic data from almost 2,000 individual birds

representing 1,287 species across the new world. Over 2,000 genes were sequenced for each individual. These birds all belonged to a handful of songbird families. including the mega-diverse tyrant flycatcher family. I used to do this kind of research, and I can tell you that this is an impressive amount of genetic data. The researchers took all that data and used fancy analyses and statistics to construct a detailed evolutionary tree, a phylogeny of all these bird species.

A phylogeny is a branching diagram that shows the genetic relationships and evolutionary history of the critters in question. The critters in this case being individual birds from those 1,287 species. By itself, the phylogenetic tree produced in this study is a really cool thing and was worthy of publication. But it's what the researchers did next that made their study extra exciting and got it published in the journal Science. The researchers took their tree, the phylogeny, and ran it through some other fancy computer analyses to calibrate it on the geological time scale. With a time calibrated tree, it's possible to estimate how long ago two species or lineages split from

each other. So the time calibrated tree allowed the researchers to figure out the rates of species formation in the different bird lineages, the different branches on the tree. By looking at speciation rates, as well as the geographic ranges of the various bird species and lineages, the researchers came up with some fascinating results. They found that new bird species evolve more often in temperate and Arctic regions than in the tropics. But that seems counterintuitive, right? Since we would probably expect speciation rates to be highest in the tropics.

After all, that's where most of the species are. I mean, you can go birding in South America and see 300 or more bird species in a day. It's out of control down there. In North America, it would be a major accomplishment to find 300 bird species in a month. Based on their results, the researchers suggest that new species form at higher rates in regions where there aren't so many other species. Maybe it's easier for new bird species to evolve in places where competition from other species is minimal. This might be what's going on in the temperate and arctic latitudes. By this way of looking at things, the tropics may have more species today

only because the ecosystems there are more ancient and more environmentally stable. Species might not wink out and go extinct as often in the tropics. New bird species have been evolving and then piling up in the tropics for millions and millions of years. So bird species may evolve more often in colder, harsher environments because there's less competition from other species. But they probably go extinct way more often in those same places. Life ain't so easy in temperate or dry places like high mountains or most of North America. Wherever extinction outpaces speciation in birds, the end result is a relatively low number of species. And birders in these places will have to work that much harder.

All right, let's move on to our next study. But first, I'm going to take my customary coffee break. And while we're standing around, I have a favor to ask of you. If you're grooving on the Science of Birds podcast, if you find it educational, hilariously entertaining, whatever, it would be so great to get a review from you. If you're listening on Apple Podcasts, you can leave a review right there in the app, at the bottom below the list of episodes. If you're listening on Spotify or another app, the best place to leave me a review is podchaser.com.

Podchaser is a free resource for people who love podcasts. I'll put a link in the show notes to the page where you can leave a review. Now, if you're new to Podchaser, you'll need to create an account first, but it's quick and easy. Reviews help other bird lovers find this podcast, so thank you for taking a moment to help out. Now, let's get back to our 2020 studies. The fourth study has to do with the connection between bird migrations and seasonal changes in vegetation. In temperate regions of the world, winter is generally a time when there isn't so much green vegetation. Compared to summer, winter is a relatively dreary and not so colorful time.

But as the days get longer and spring approaches, plants grow and put out new leaves. The landscape greens up, starting in the south, and moving northwards as spring and summer progress. You can imagine this like a slow-moving wave of green flowing across. the continent from south to north. In the field of ecology, there's actually something called the Green Wave hypothesis. This hypothesis predicts that herbivorous birds and other animals that migrate long distances will follow the green wave of spring growth as it flows north. Likewise, these animals will return south as the green wave recedes in autumn. This mostly applies to North America and Eurasia.

The Green Wave Hypothesis has been supported by research on geese and some other birds, as well as migratory mammals like bison and elk. The study we're looking at here was published in the Journal of Animal Ecology. The authors are Frank LaSort from the Cornell Lab of Ornithology and Catherine Graham from the Swiss Federal Research Institute. These researchers wanted to test the Green Wave hypothesis, and the way they did it was pretty cool. They combined an immense amount of data on bird locations across the western hemisphere with vegetation data taken from satellite images. They analyzed the associations of multiple bird species with the amount of surface greenness over the seasons. But this study didn't look at only a few bird species, and the time frame wasn't just a single year. The data here included

230 bird species from North, Central, and South America. Observations of all these birds were gathered over 13 years from 2006 to 2018. That's a serious mountain of data. This seems to be a theme here, doesn't it? Every study we've talked about so far has depended on a massive large-scale data set. We have bird song recordings from over 5,000 species, hundreds of whole genomes, sequenced for most of the world's bird families, and thousands of genes sequenced for 1,200 new world songbird species to generate a detailed phylogeny. Good stuff.

Now, it's not like the two authors of this Green Wave study could possibly generate data like that all on their own, not even if they had an army of slave-like graduate students doing their bidding. There's a reason this paper was published in the Citizen Science category. in the journal. That's because the researchers got their bird data from e-bird. As you probably know, e-bird is a vast online database of bird observations from across the world. The overwhelming majority of the people submitting observations to e-bird are not professional ornithologists. Most of them are simply enthusiastic birders and naturalists. The data they collect is used in projects like the one we're talking about today.

So those of us who use e-bird to record our bird observations are citizen scientists, like totally for real. And dig this. If you submitted bird observations from anywhere in the Americas to e-bird between 2006 and 2018, there's a good chance your data made it into this study. How cool is that? So the researchers wanted to figure out how birds with different diets respond to the green wave, during their migrations.

You'd expect grass and leaf-munching birds to move north with the flush of new green growth in spring. But do they really? And what about birds that specialize in eating seeds or insects or small mammals? In ecology, one way of categorizing critters is by their dietary guild. Insectivores make up one guild. Herbivores are another guild. Carnivores are a guild, and so on.

The species in a guild can be totally unrelated, in the genetic sense. All that matters is what resource they use for food. So in this study, the researchers divided the 230 bird species into seven dietary guilds, and then they ran their analyses. First off, they found that, across the board, birds in the Western Hemisphere do time their migratory movements to follow the green wave closely over the seasons. For the most part, anyway. This is a nice confirmation of the Green Wave hypothesis. But there were some differences across the dietary guilds in how much they surfed on the Green Wave. The strongest association was for

omnivores, herbivores, and granivores. Granivores are seed eaters. There were also some regional differences in the degree of association with vegetation greenness. For example, carnivores that migrate along the western flyway, along the western edges of North and South America, they had the weakest association with the Green Wave. You are no doubt a smart cookie, so you can probably imagine why this kind of research is important. Sure, it's great to increase our understanding of basic ecology, like understanding how birds follow vegetation patterns during migration. But what are the bigger implications of this study?

If the timing and geography of bird migrations depend on where the vegetation is green, how might climate change mess with all of this? What's going to happen to our birds when vegetation patterns change? Plants respond quickly and dramatically to changes in temperature and rainfall. Will birds migrate differently as plants shift their distributions in a warmer world? This study tells us that the answer is probably yes. I guess we'll have to see. Our fifth and final study has to do with how birds can save the world.

You think I'm kidding, but I'm not. One recurring theme in 2020 is that nature can bring us relief from stress and provide us a healthy means of escaping the craziness of the human world. Time spent in nature improves our well-being. As so many of us have been locked down, stuck at home, the importance of birds as ambassadors of the natural world has become more apparent than ever. Actual scientific studies in biology and psychology have shown that nature is good for us. But what are the actual sensory cues that matter to us as we're out sauntering around in nature? What exactly is it that improves our well-being, besides just fresh air and exercise?

This study was conducted by a team of American researchers, and it was published in the Proceedings of the Royal Society, B. The B stands for biological sciences. If you think that journal title is a mouthful, the earlier title was even longer. It used to be... Proceedings of the Royal Society of London, Series B, containing papers of a biological character. Seriously, that was the title. And my apologies to my listeners in the UK.

I know my British accents are way off, but I can't help myself. Sorry, guys. So, in this study, the researchers wanted to test whether bird songs in a natural setting influence people's sense of well-being. They used a fun experimental approach to get some answers. The study was conducted in Boulder, Colorado, on two hiking trails. The researchers placed 10 hidden speakers along each trail. They played bird songs from these speakers from 9 a.m. to 3 p.m., five days a week,

including the weekends. They played songs from 11 bird species, including American Robins, House Rens, Yellow Rumped Warblers, and Pygmy Nut Hatches. The researchers called their artificial bird songs a phantom chorus. I just love this name, Phantom Chorus. It sounds all spooky and Halloween, but it's just a bunch of recordings of tiny birds singing pretty songs. Hikers on the two trails in Colorado would be walking along, hearing this phantom chorus getting punked by the researchers. These birds' sounds were broadcast for one week,

and then the next week they were turned off. So they alternated. This allowed the researchers to compare their results with and without the phantom chorus treatment. I should say that this study took place from mid-July to September. That's not when you'd expect to hear many birds singing. So I wonder what happened when an experienced birder was hiking on the trail.

A birder would be like, wait, do you hear that? Why are there so many birds singing? It's friggin' August. Then maybe the birder would investigate the source of a spotted tohi song coming from some low bushes. The birder would scramble around and then discover the hidden speaker. Can you imagine what they would be thinking? It would probably make them question the reality of everything, including their own existence. Am I in the Matrix?

Anyway, when a hiker reached the end of the trail, a clipboard-wielding researcher would pop out and accost them. The hiker was asked a series of survey questions. Questions like, based on your experience on the trail today, about how many different types or species of birds would you say are in the last quarter mile or last seven minutes of your wife? on the trail. Then each hiker was asked to rate how much they agreed with statements like sounds on the trail today make me wonder about things, and hearing sounds on the trail today made me feel free from work, routine, and responsibilities. The results of this experiment showed that people hiking on these trails with the phantom choruses reported higher levels

of well-being than without the choruses. The restorative effects of the experience were, for some hikers, linked to their direct perception of the bird sounds. For others, it was more about their perception of the biodiversity along the trail. Pretty neat, huh? It turns out birds are good for you in more ways than one. If more people got out into nature, they'd hear more bird songs, and they'd probably have better mental and physical health.

See, that's one way that birds can help save the world. But now I'm going to be suspicious every time I go for a hike. Is that bird I'm hearing even real? Is anything even real? And if I actually see the bird, I'll wonder if it's just a Disney-style animatronic robot or something. So I just wanted to take a moment to do a little personal note here. You know, I'm going off script. In case it's not obvious to you, I write a pretty lengthy script for every one of these episodes.

So right now I'm not talking on script. So if my grammar is poor or there's a lot of ums and all that kind of stuff, then you'll know why. So in case you don't know, one of the things that I do for my sort of day job is I am a birding guide. I have a small business. I have a business partner. And I take small groups of people to really cool place. around the world to show them birds, birds and other amazing natural wonders. So I am basically a professional naturalist and I feel super, super lucky to have the opportunity

to do that kind of work. But then, of course, 2020 came along and travel pretty much ground to a halt. And so, you know, I haven't been able to lead a tour since, yeah, pretty much all year. so but you know i'm i'm thankful that i got to be home with my wife and spend more time enjoying the yard and that kind of stuff and interestingly the time that i had available at home allowed me to do this to start the science of birds podcast what you're listening to right now had 2020 not happened i don't know when i would find time to do something like this i had the idea so i was already thinking about doing this, but, you know, it just became an obvious thing that I should do once I wasn't able to travel anymore. And I'm really, really thankful that I could do it,

because I have absolutely loved every moment of it. And I'm really proud of what I've been able to accomplish. And I'm super excited about where I'm going to go from here, about, you know, new episodes throughout next year. And, you know, just how I can build an audience and serve you guys really well and just make interesting stuff for you and educational stuff. So, so thank you for being part of the beginning of this podcast, the first few months. It's been really amazing. I've got a lot of really very kind, very wonderful comments from you guys and nice reviews. So thank you, thank you, thank you. So as always, I would be delighted to get an email from you. You can email me at Ivan at scienceofbirds.com. And if you're interested in checking

out the show notes for this episode. It's episode 19. You can go to the Scienceofbirds.com website and see those there. Happy New Year and I'll see you next time. Peace.