The Science of Birds - Female Birdsong

Episode Date: April 19, 2022

This episode—which is Number 50— is all about Female Birdsong. Songs are one of the things we love most about birds. They define the soundscapes of the natural world. Even though humans have been surrounded by singing birds for millions of years, we still have some misconceptions about birdsong. Today’s episode is about a misconception of sex differences in birds… Of who sings and who doesn’t.~~ Leave me a review using Podchaser ~~Links of InterestThe Forgotten Female: How a Generation of Women Scientists Changed Our View of EvolutionFemale Bird Song ProjectVideo of Superb Fairy Wren female SingingSinging female Cerulean Warblers [Video]Link to this episode on the Science of Birds websiteSupport the show

Hello and welcome to the podcast. This is the Science of Birds. I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted, guided exploration of bird biology for lifelong learners. This episode, which is number 50, is all about female bird song. Songs are one of the things we love most about birds. They define the sound escapes of the natural world. In tropical regions, there are birds singing at pretty much any time of year.

Further from the equator, in temperate ecosystems, most of the singing occurs only during the warm months of spring and summer. Even though humans have been surrounded by singing birds for millions of years, we still have some misconceptions about bird song. Today's episode is about a misconception of sex differences in birds. Of who sings and who doesn't. If you were born some time in the last 100 years, and I suspect you were, there's a good chance you were taught that only male birds sing.

That's certainly what I was taught. We were told that males sing to attract females. You might also recall learning that both the songs and colorful plumages of males evolve through the process of sexual selection. Charles Darwin, good old Chuck E. came up with the idea that sexual selection is the process by which songs and fancy plumage evolved in the first place. While most of that may be true, the part about only males singing definitely isn't. Only in recent decades have ornithologists come to realize how common it is for females to sing. It's taken over 150 years since Darwin's time for scientists to finally appreciate the importance of female birdsong.

Why did it take such a bloody long time to figure this out? Well, it has to do with bias. Of course, scientists are not supposed to have biases when they do research. They're supposed to be objective as they do their work, free from any emotions, or preconceived ideas that might contaminate their findings, sort of like robots or vulcans. But scientists are human. We humans all have our biases,

whether or not we're aware of them. I mean, I don't have any biases. I'm always 100% fair and objective. I see the world exactly as it is, unfiltered by any prejudice or cognitive distortions. but hey, that's me. We're not talking about me. But many ornithologists back in the day apparently did have some biases. One bias had to do with geography. A lot of the early and influential research on birdsong happened to be done by scientists living in the Northern

Hemisphere, in Europe and North America. Those dudes tended to study birds in their own backyards. In other words, bird species from northern temperate regions. But it just so happens that females of most breeding birds in these regions don't sing much. A much higher proportion of species in tropical regions have females that sing their little hearts out. If early studies had been focused in the tropics, we probably would have accepted female songs as being a common thing from the get-go. So you can see how there was this geographical bias in ornithology. And when I said dudes a moment ago, I meant male dudes, men.

The vast majority of professional ornithologists in the 1800s were male. They were white men of European ancestry. They wore stern expressions and bushy beards or silly mutton-chop sideburns. So gender bias probably played a significant role, too. Male researchers paid more attention to male birds, especially since those male birds were often more colorful and conspicuous. It took a very long time, yes, but people in the scientific community finally looked at themselves in the mirror to see that biases have clouded their view of bird song all these years.

Biases of geography and of gender. These days, it's common knowledge among ornithologists that female birds of many species sing. Sure, it might be sort of rare in the temperate latitudes, but it's not a rare thing at the global scale. Now that our eyes and our ears are open, now that we have this newfound perspective on female, bird song, let's look back in time at the evolutionary origins of this behavior. I should point out that our focus today is on birds in the order Paseraformis. These are the songbirds. We also call them passerines or perching birds, right? And remember that about half of all bird species are in this group. Lots of recent studies have looked at the origins of songbirds.

researchers have used molecular genetic techniques, anatomy, biogeography, fossils, and other sorts of data. And what has all of this research found? It's found that songbirds first became a thing in the land down under in Australia. These little darlings first evolved in that region about 50 million years ago, give or take 15 million years. Today, there's a ton of of songbird diversity in the Australasian realm. Diversity in species, but also in bird families. And singing females are common in many families across this region. Here's a female Gilbert's Whistler, Pachycephala in Orneda, singing in New South Wales, Australia.

Again, that was Gilbert's Whistler. Whistlers are in the family Pachycephalian. Now consider the fairy wrens of the family Malurity. These hyperactive little birds live in groups. There's a lot of interesting stuff about their biology and how they breed, including the fact that female fairy wrens sing a lot and they sing loudly. In some fairy wren species or populations, female songs are very similar to those of their male counterparts. But in other cases, the females sing somewhat differently. Females share in the duty of defending the territory.

It seems that's one reason they sing. I couldn't find any great recordings of a singing female fairy wren to play for you, but I'll put a link in the show notes to a YouTube video of a superb fairy wren female singing. That's not me praising the bird saying it's superb. I mean, I would totally say something like that, but the actual name of the species is superb fairy wren. Female bird song is common, not only among Australia's Passerine Avifana. It's also common in other tropical regions around the world.

Females belt out their tunes in Southeast Asia, Africa, and South America. Here, for example, is a singing female orange-bellied leaf bird in Malaysia. And on the other side, side of the world, in the mountains of Ecuador, we have a female bar-winged wood wren. Recent studies using evolutionary trees have looked at how female song is sprinkled across the many families in the order Pasariformis. One important study, published in the journal Nature Communications in 2014, came to the conclusion that female song was present in the ancestor of all songbirds.

So that was the ancestral condition. The great, great, great, great, great, grandma of all songbirds was herself a songstress. But what about all those songbird species in northern regions where the females don't sing or sing very little? Why didn't they inherit grandma's ability to sing? Well, many ornithologists now think that females, song in those species has been lost over evolutionary time. Natural selection, for one reason or another, has stripped away female singing behaviors from their genetic code. Not just once,

but again and again in different bird lineages. Not only did the most ancient female songbirds sing, some studies suggest those females were just as colorful and flashy as their male partners. The extreme color differences we see today between the sexes of many species evolved later. They evolved secondarily. In species after species, females have evolved to become more drab and inconspicuous. And in many of those same species, females stopped singing. An interesting 2009 study on New World Blackbirds made a good case for this scenario. The researcher looked at the evolutionary tree of this family, the family Icturidae. These are the blackbirds, orioles, meadowlarks, caciques, grackles, and so on. For 65 species in this family, the researchers

mapped out places on the family tree where, over evolutionary time, certain branches, or lineages of blackbirds went from having female song to not having it. This study showed how blackbird's species have repeatedly shifted their ranges from their tropical origins into the northern temperate zone. And those shifts seem to go hand in hand with losses in female bird song. And on top of all that, the females that lost their singing behavior were the ones that also tended to lose their bright colored plumage. Blackbird species that live all year in the tropics today have females that sing and are just as colorful as their mates. One big take-home here is that the differences we find between male and female songbirds

don't necessarily exist only because males have become more and more vocal and colorful over time. More likely, it's females that have become less and less vocal and colorful. Why would that happen? Did the female blackbirds get depressed or something when they left the tropics behind and moved to bleak northern places? Maybe they were filled with Unwee and gave up on trying to look pretty and couldn't bring themselves to sing happy songs. Because what's the point of it all, right?

No, it turns out there's a better explanation for why female blackbirds of many species stopped singing and lost their color. It has to do with changing sex roles. Compared to the tropics, the summer birds, the summer birds, breeding season is short in temperate latitudes. When some species shifted their ranges north, the challenges of that brief season seem to have forced some big changes in the roles of males and females. Females came to specialize in building the nest and incubating the eggs. Males do their part by defending the territory, being all colorful and conspicuous as they sing loudly and chase off rivals.

The female may have evolved to be relatively quiet and camouflaged so that she doesn't attract predators to the nest. So northern species like this evolved to have a division of labor between the sexes. In contrast, males and females in the tropics probably look and sound similar because they have similar roles. They share a territory all year long and they both defend it. Tropical males and females use songs for more or less the same reasons, to defend the territory, to attract mates, to brag to the world how great they are, and all of that. This might be what was going on 50 million years ago with that ancestral songbird species in Australia. Males and females back then probably worked together and played similar roles.

But starting about 27 million years ago, songbirds moved north out of Australia, diverging sex roles may have led to the loss of female songs in some lineages. Even then, it's estimated that today, around 64% of all songbird species have singing females. All of this is a big deal. It's pretty much a 180 from what Darwin thought about the origin of bird song. He thought males got better and better at singing from one generation to the next because females choose males with the best songs. Okay, well, that's actually true. I guess he was right about that part.

Good job, Darwin. Ah, but what Darwin didn't know is that all female songbirds used to sing once upon a time. Instead of the original ancestral condition being no singing for either sex, it was actually both sexes singing, and then later females in some lineages lost. their singing voices. We can credit this exciting paradigm shift about female bird song to the work of many scientists. However, most of the key research on this topic is being done by women. There was even an entire study that proved this using statistics.

That study reviewed dozens of published papers on birdsong. in both female and male birds. The results revealed that of all the papers on bird song in general, women were the primary authors only 44% of the time. So still a little male bias there. But for the papers that focused on female birdsong, 68% of the lead authors were women. One name you'll see popping up all over the place in this field

is Dr. Karen Odom. She's an author on many recent and important papers on female song. Dr. Odom also started the Female Bird Song Project. This is a citizen science project that encourages average blue-collar folks like you and me to record female bird songs and then upload them to either E-Bird or Xenocanto. The more verified recordings there are

of singing females in these public databases, the more data there is for scientists to analyze. You can check out the Female Birdsong Project by going to femalebirdsong.org. I'm sure we'll see lots more research on this interesting topic in the coming years, and more eye-opening discoveries. Indeed, ornithologists continue to learn more about how songs are used by females in temperate breeding species. Even though female songs are more common in the tropics, you can certainly hear females singing in temperate parts of the world. Here's a female Northern Cardinal, for example,

singing in Ontario, Canada in spring. As for examples of new discoveries, it was only a few years ago that female Cerulean warblers were recorded singing for the first time. I'll put a link to one of these recordings in the show notes. So now that we're paying more attention, it seems like we'll probably find more and more examples like this of songs being sung by female birds. And that's just fantastic. This whole thing should make us wonder, though,

what other biases do we have that are distorting our view of birds and of the natural world? And what will the next big paradigm shift be when we realize that what we've been taught all these years is totally bogus. Now, that might sound like I'm being a bit negative, but I don't mean to. I love the scientific process, and that's how science works. We do our best to understand nature with the information we're given. Then, if we get new information, new data, we update our view of the world and let go of the past.

and when we realize we have a bias that's clouding our view, we let that go to. I wonder how much you knew about female bird song going into this episode. Were you aware it was a thing? I have to admit that until not that long ago, female song was not really on my radar. So it was great to dig into this topic with you today. I hope you learned something. I'll certainly be looking and listening for singing females from now on when I'm out birding. And hey, you know what?

This is episode 50 of the Science of Birds podcast. It feels great to reach this milestone. When you start a project like this, you never really know how far you're going to take it. I always intended to be in it for the long haul, but until I was out of it, actually doing it for a while, I had no way of knowing how much I would love it. And I do love it. It's been an amazing experience so far. I look forward to reaching episode 100 and to all the episodes in between and beyond. So thank you for being on this journey with me. Also, I figured out that, on average, the script I write for each episode has about 5,800 words, on average.

multiply that by 50 episodes and you get 290,000 words. What? That's crazy. For comparison, the average science fiction or fantasy novel is around 100,000 to 150,000 words. So, for this podcast, I've already written the equivalent of two or three novels. I had no idea, but how cool? it's been a long time dream of mine to write some fantasy novels seriously so at least i've proven to myself i can sit down and write a lot i just looked it up and i guess the title harry potter and the sorcer's stone is already taken dang maybe i could go with a bird theme and call my first book harrier potu and the soras stone chat you see because those are all bird names Harrier, Potu, Sora. Ha ha! If you'd like to hear more stupid jokes like that,

you can support this podcast by becoming a patron. If you're interested, just pop over to my Patreon page at patreon.com forward slash science of birds. You can also shoot me an email if you have something you'd like to share with me. Perhaps a comment about the podcast or about some biases you have, but that you don't know you have. Whatever the case, my email address is Ivan at Scienceofbirds.com.

You can check out the show notes for this episode, which again is number 50, on the Science of Birds website, scienceofbirds.com. This is Ivan Philipson, wishing you a great day wherever you are. Peace.