The Science of Birds - Awesome Things We Learned About Birds in 2021

Episode Date: December 30, 2021

2021 is over, yo! So it's time for the Annual Review Episode! We’ll be looking back at some highlights of bird science in the year 2021. What fascinating things did ornithologists and other biologists discover about birds this year?I’ve picked 5 studies to highlight for you. These are stories that, in most cases, were interesting enough to make the news.~~ Leave me a review using Podchaser ~~Links of InterestVIDEO: A snoozing fox meets a plucky little black-crested titmouseVIDEO: Tapaculos Hunt for TrufflesReferencesBird neurocranial and body mass evolution across the end-Cretaceous mass extinction: The avian brain shape left other dinosaurs behindShape-shifting: changing animal morphologies as a response to climatic warmingFacultative Parthenogenesis in California CondorsLifetime reproductive benefits of cooperative polygamy vary for males and females in the acorn woodpecker (Melanerpes formicivorus)Global abundance estimates for 9,700 bird speciesDrones and deep learning produce accurate and efficient monitoring of large-scale seabird coloniesA supergene underlies linked variation in color and morphology in a Holarctic songbirdA new genus and species of tanager (Passeriformes, Thraupidae) from the lower Yungas of western Bolivia and southern PeruDiscovering the Role of Patagonian Birds in the Dispersal of Truffles and Other Mycorrhizal FungiWhat the pluck? The theft of mammal hair by birds is an overlooked but common behavior with fitness implicationsLink to this episode on the Science of Birds websiteSupport the show

Hello and welcome. 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 is episode 42. And because the year is almost over, this is the annual review episode. We'll be looking back at some highlights of bird science in the year 2021. What fascinating things did ornithologists and other biologists discover about birds this year?

I've picked five studies to highlight for you. These are stories that, in most cases, were interesting enough to make the news. Well, they were on my news feed anyway. The Google Algorithm knows what I like. I like news about birds, of course, but also feel-good stories about puppies and kittens, and Hollywood Gossip and cryptocurrency. That's pretty much it. And I hope you can tell that I'm kidding about some of that.

I wasn't kidding about the puppies, though. Anyway, I chose these five studies because I find them quite interesting, and because I think you will too. This is in no way a comprehensive review of all the research published about birds in 2021. Thousands of papers about birds were published this year. I did not meticulously combed through massive stacks of scientific journals to select the top five papers at the pinnacle of scientific rigor and significance. Ain't nobody got time for that.

So these are just some cool studies that caught my attention. We'll take a few minutes each to talk about them. If you're interested in digging deeper, I'll put links to the studies in the show notes on the Science of Birds website. At the end of the episode, I'll wrap up with a little personal note about how the podcast is doing and all that jazz.

All right, let's do this. The first study has to do with bird brains, dinosaurs, and extinction. As we all know now, birds are dinosaurs. Birds represent the only lineage of dinosaurs that survived the great mass extinction that happened 66 million years ago. You know, when that seven mile wide asteroid smashed into Earth and all hell broke loose? Why did birds survive that cataclysm when every other type of dinosaur bit the dust? Scientists have been scratching their heads about this for years,

coming up with various hypotheses. One hypothesis is that birds survived because they're small. No land-dwelling vertebrates weighing over 55 pounds or 25 kilos survived the extinction. All the big boys died. It seems that small critters had a survival advantage. Or maybe having beaks gave birds the advantage they needed. They could eat a wide variety of food resources, whatever hard-shelled seeds or scraps were lying around in the smoldering ruins of the world.

Another possibility is that the power of flight is what allowed birds to make it through the extinction. A flying bird could cover great distances with relative ease, so it could be efficient in its search for food, or water, shelter, and so on. And then there's intelligence. Birds today are super smart, and it seems likely that their ancestors, 66 million years ago were also intelligent. Smarter than your average triceratops anyway. So another hypothesis for why birds survived the asteroid strike is that their superior brains allowed them to navigate the tumultuous, unstable environments in the aftermath.

The 2021 study we're looking at here, published in the journal Science Advances, gave us some fresh evidence in support of this intelligence hypothesis. At the heart of this research was a remarkable 70 million-year-old skull. It belonged to a bird-like creature called Ictheornus. Ictheornis is closely related to the ancestor of all modern birds. Other than the pointy teeth sticking out of its beak, it probably looked something like a modern gull or turn. The nearly complete fossil skull, with its toothy beak, was discovered in Kansas.

It's so well preserved that the researchers could use CT scanning, to reconstruct a simple 3D model of Ictheornis' brain. This was a very rare opportunity, because fossils of most primitive bird skulls are crushed or mangled beyond the point of being useful for studying the brain. Consider the brain of a non-avian dinosaur, like Tyrannosaurus rex. It has a linear arrangement. The sub-regions of the brain are lined up like train cars.

In simple terms, the engine of our Choo Choo Choo, the front is the cerebrum. Behind that is the midbrain, including the optic lobes, and the cerebellum is the caboose. This is considered the ancestral, primitive arrangement of the dinosaur brain. The brain of Ictheornis, however, is proportionally larger. It's more advanced. Compared to T-Rex and his buddies,

Ictheornus's brain has an expanded cerebrum and cerebellum. Also, the optic lobes are shifted, downward, a bit more underneath the cerebrum rather than behind it. Archaeopteryx, another famous prehistoric cousin of modern birds, has a similar brain architecture. Modern bird brains show a continuation of these trends. Birds today have an even larger brain overall, with a greatly expanded cerebrum. The highly developed optic lobes in modern birds have shifted to sit beneath the cerebrum. This brain rearrangement and expansion in the evolution of birds went hand in hand with the

improvement of their vision and flying abilities. Big brains and superior eyesight were evolutionary innovations that marked a big leap forward. They might be what distinguished the first true ancestors of modern birds, who were flapping around millions of years ago before the big extinction. So this recent study was newsworthy because, one, it used a beautifully preserved fossil to reconstruct the brain of Ictheornus, a bird-like dinosaur that lived 70 million years ago. And two, it shows us how the brain of Ictheornus was intermediate between non-avian dinosaurs and modern birds. Ictheornus was one of the closest relatives of modern birds that we know of, But it didn't survive the Cretaceous Paleogene extinction event, nor did any other close

relatives of birds. Only the lineage of modern birds survived. Did Icythiornis go extinct because it wasn't smart enough? Because it didn't score high enough on the SATs? Because it couldn't solve a Rubik's cube in anything less than three hours? Who knows? But the fact is, this study adds more evidence to the idea that big brains, intelligence, and maybe advanced sensory systems like eyesight were essential tools for survival in the dinosaur apocalypse. Study number two is about evolution happening today, as in right now. And this study is also very much about climate change. Human-caused climate change is having countless effects on the natural world. From our human perspective, we think of these effects as mostly bad news. One of our fears

is that global warming and other changes are happening so fast that animals and plants won't have enough time to adapt. Maybe they won't be able to evolve quickly enough to avoid extinction. It's true that genetic adaptation through the process of natural selection can be a slow, gradual process, taking thousands or millions of years. But sometimes evolution can happen seemingly overnight. Biologists have discovered lots of cases of animals adapting to changing environments in just one or a few generations. Perhaps the most famous example is the Galapagos finches. Scientists have documented how the beak shapes of these birds have changed significantly in response to shifts in food availability during and after droughts. This is contemporary

evolution, happening from one year to the next, one generation to the next. The research we're looking at here is a paper published in one of my favorite journals, Trends in Ecology and Evolution. It's a review of studies that show how at least 30 warm-blooded animal species, both birds and mammals, have been changing shape in the modern human era. These are species from all over the world. Specifically, the study reports evolutionary changes in the sizes of animal appendages, ears, legs, tails, and beaks. There's evidence that in the last 100 years or so, beak sizes have changed rapidly in some birds.

Birds like parrots in Australia and dark-eyed junkos in North America. The changes aren't dramatic, usually on the order of 10% or less, but they're significant. They are happening. According to this study, appendages in birds and mammals are getting larger in many species. This fits the idea that increasing temperatures around the globe are causing these seemingly evolutionary changes, because larger appendages like beaks, help an animal keep cool to get rid of excess heat more easily. Okay, now actually I have a second related study for you.

This is a two-for-the-price of one deal. The second study was published in Science Advances, the same journal with our Ictheornis skull study. Here, researchers analyzed data from 77 bird species in the Amazon basin. Mass and wing-length measurements were recorded for over 10,000 individual birds over 40 years at one location. That's a pretty impressive data set. The authors of this study looked for trends over time in the bird's body measurements. What they found was that all 77 bird species had decreased in body mass in the last 40 years, and about one-third of the species had shifted

toward having longer wings over the same period. The best explanation we have is that these changes are being driven by a warming climate and more severe extremes in seasonal rainfall and temperature. The researchers ran statistical tests on all of this, and so there's some data to back this up. They propose that birds in this remote part of the Amazon rainforest might be decreasing in mass and getting longer wings because this would help them conserve energy and keep cooler. A smaller body with larger wings results in lower wing loading. Birds with low wing loading fly more efficiently and they generate less body heat. These two interesting studies highlight how birds around the world have been changing shape over the last century.

Some of these are probably examples of contemporary evolution, where natural selection is molding the genomes of these birds. In any case, there are good reasons to believe that climate change is the driving force behind all of this shape-shifting. So what I'm hearing here is that if birds can grow larger beaks, longer wings, and smaller bodies within just a few decades, they're all going to be okay, right? They'll simply adapt to whatever we throw at them in terms of climate change. We can just keep on burning fossil fuels, eating beef, and cutting down forests like there's no tomorrow. Not so much, actually. We still have no idea if any bird species will be able to evolve quickly enough to survive the crisis of climate change. Some of them probably will adapt,

but many others almost certainly won't. If a bird species can't adapt genetically to the new normal, if it doesn't evolve, it's left with only two other choices, relocate or go extinct. The third study today, which I know, is actually the fourth study, but just play along, okay? The third study has to do with virgin birth. That's right, virgin birth, but in non-human animals, mind you. This is the situation where a female pops out a baby, even though her egg was never fertilized by a male.

It's a type of asexual reproduction, and the technical name is parthenogenes. We see this interesting phenomenon here and there across the animal world, in creatures we normally think of as reproducing only sexually. Examples of parthenogenesis occur in frogs, lizards, sharks, and insects. There are several ways this can happen. We don't have time to get into all the details, however, so just know that in parthenogenesis, only the female contributes genes to her offspring. There's no male contribution. Birds are not really known for being awesome at virgin birth. There have been cases of chickens, turkeys, pigeons, pigeons, pigeons, and zebra finches sometimes producing eggs this way. But the chicks inside those eggs don't usually survive to the

point of hatching. They don't see the light of day. But lo and behold, this year scientists discovered not one but two independent cases where a captive California Condor successfully produced a viable chick through parthenogenesis. Two different females had babies through virgin birth. This made headlines all over the place. It was a shocking discovery. People across the nation took to the streets where soon there were crowds of ecstatic bird enthusiasts going absolutely bonkers. Intoxicated by their joy and their confusion, they shattered windows, lit fires, and flipped cars over. They mostly flipped Honda Priuses for some reason. Is it Priuses, or should it be Prii? Like octopuses, octopi. Well, it doesn't matter. This amazing discovery in

California Condors was sort of an accident. It happened during routine genetic screening of captive condors. The researchers found that the genome data from two males displayed only single copies of their genes, and those genes happened to perfectly match the genes of their respective moms. Now, to clarify, two different females, both part of the ongoing captive breeding program for the species, two different females each independently produced a single male chick via virgin birth. So this has happened at least. least twice in condors. It's not a one-off fluke. And get this, each of these females was housed with a fertile male, which had already fathered other chicks with her. Often the assumption is that

parthenogenesis occurs naturally only when males are absent, or in short supply. But not in this case. The authors of this study, which was published in the Journal of Heredity, believe that their discovery marks the first example of facultative parthenogenesis in birds where the sexes were not kept apart. What does that mean? Well, facultative means occurring optionally in response to circumstances. Virgin birth is apparently sort of optional in California condors. Each of these females had a handsome, healthy male at her disposal, but nope, they chose virgin birth instead. In previous cases, with other birds like chickens and turkeys, females produced eggs like this, only when no males were around. In other words, when the sexes were segregated.

Now, unfortunately, the male chicks born from the quote-unquote virgin moms didn't have very long lives. I believe they died before it was ever discovered how special they were. One of them was released into the wild, but died when he was about two years old. The other male remained in captivity his whole life. He was scrawny and had scoliosis. He shared his home with a female, but the pair had no offspring. That male died when he was about eight years old. It's common for offspring from virgin births and other animals to have genetic and physical problems,

and relatively brief lives. No one has an answer to why this happens in condors. If it occurs in nature, maybe it's a way for condors to reproduce when population density is low. Or it may have some genetic benefits for the population. There are lots of interesting questions here. And who knows? Maybe virgin birth is more common in birds than we realize. Detecting parthenogenesis isn't easy. It was possible with these California condors because scientists have a detailed pedigree for pretty much every individual in the species. and there's genetic data for most of them too.

The California condor is a special case. For most other bird species, we just don't have this level of rich information. Anyway, cool stuff, right? Our next study has to do with cooperative breeding in woodpeckers, and it highlights the scientific value of long-term. term field studies. Acorn woodpeckers, melanerpe's pharmacivorous, have been studied at the Hastings Natural History Reservation in California since 1974. The individual birds in the population have

colored bands on their legs. Genetic information from every bird allows researchers to know exactly who is related to who among the woodpeckers. There's a detailed family tree for the entire population of hundreds of birds. Added to all that is a rich history of behavioral observations. I'll definitely do an entire episode on the acorn woodpecker at some point. It's one of my favorite species. These little guys are noisy, funny, and highly social. Acorn woodpeckers have a complicated breeding system.

Sometimes they breed in the usual one male, one female arrangement. Good old straight-laced vanilla family values. Boring. But at other times, these woodpeckers practice cooperative polygamy. Groups of between one and eight males shack up with groups of groups of one to four females to raise a single brood of chicks. So the eggs in a single nest can represent the products of multiple fathers and multiple mothers. In these groups, co-breeding adult birds of the same sex are pretty much always close relatives.

For example, a pair of males in the group might be brothers, or perhaps father and son. And if that isn't wacky enough for you, on top of there being co-breeding males and females sharing a nest, there can be one to ten so-called non-breeding helpers in the mix. These are young birds born to a particular group of adults who stick, around to quote-unquote help. They don't disperse and they don't breed. Instead, they help to feed the chicks in this year's brood. Helpers at a nest are typically between one and five years old. They might help for a few years, then head off to start families of their own. Okay, let's talk about this study published in 2021. It's from the journal Proceedings of the Royal Society

B. That's B as in biological sciences. The studies authors wanted to quantify the lifetime reproductive success of acorn woodpeckers. What is lifetime reproductive success? Here, it's the number of babies that fledged per adult woodpecker. For example, imagine there's a male woodpecker. Let's call him Barron Heathcliff Hickenbottom III. If Heathcliff lived to be 15 years old and he sired 32 chicks that successfully fledged, 32 would be his lifetime reproductive success. The researchers in this study were interested in how reproductive success might vary under different breeding scenarios. How does reproductive success in birds that nest in lone pairs differ from the success of those that nest with two or three

co-breeders? Because acorn woodpeckers have been studied so carefully and for so long at the Hastings Reservation, there was a boatload of data to use for answering this research question about reproductive success. There was 43 years of data for 499 breeding adults. That is really, really impressive. It's yet another example of how valuable it is to have data from long-term research projects, like the study of body and wing shape in Amazonian birds that we talked about a few minutes ago. So what were the results for our woodpeckers? It turned out that male acorn woodpeckers, who, work together as co-breeders in either duos or trios, had higher lifetime reproductive success.

Higher, that is, than those males who bred alone with a single female. But there are trade-offs to each strategy. Males who breed in lone pairs have more babies in the short term, but it looks like not as many over their lifetimes. For females, the results were a little different. When they co-breed in duos, they end up having pretty. much the same lifetime reproductive success as single-breeding females. So no real advantage or disadvantage either way. Take it or leave it. But when females co-breed in trios, with three females in a

single nest, those birds had the lowest lifetime reproductive success. So cooperative polygamy seems to have obvious advantages for male acorn woodpeckers. But for females, it's neither here nor there. or there may even be disadvantages. The thing is, cooperative polygamy exists in this species. It evolved for some reason, right? The authors of this study point out that they only calculated the direct reproductive success of each bird. But when it comes to passing on your genes from one generation to the next,

there's also something called inclusive fitness. This is where you factor in the genes that your sisters, brothers, and other relatives are also passing down, because your relatives share some of your genes. So genetically, evolutionarily, both direct reproductive success slash fitness and inclusive fitness are important. Maybe female acorn woodpeckers who share a nest with their daughters, sisters, and mothers do pass down more genes to their offspring overall. Maybe they really do have an advantage when they co-breed like this. Future research on this population will hopefully shed some light on this. The hyperactive little woodpeckers of the Hastings Natural History Reservation are still being

observed and studied. I'm sure there's a lot more they can teach us in the coming decades. Okay, I want you to close your eyes. well, don't close them if you're driving a car or using a table saw or something, but just imagine seeing a pile of 50 billion potatoes. 50 billion. Can your brain conjure the image of 50 billion potatoes? Mine sure can't. That number is just way too big and my brain is way too small. The number 50 billion is central to our fifth and final study. The title of the paper is Global Abundance Estimates for 9,700 bird species. It was published in the journal, Deep Breath, Proceedings of the National Academy of Sciences

of the United States of America, otherwise known as PNAS, or P-NAS. Be careful how you pronounce that one, kids. Now, if you're still trying to picture 50 billion potatoes, you can stop now. Instead, try imagining that same number of birds. Because, spoiler alert, that's the estimated number of birds that this study came up with, the total number of individual birds of all species across planet Earth. So how did the researchers in this study come up with this prodigious number, 50 billion? Well, it's complicated, and I certainly don't understand all the fancy computations involved.

But here's my basic understanding. First, the researchers gathered abundance data from, 724 well-studied bird species. This was data from previous studies by other scientists. Next, they used statistics to find the relationship between A, the abundance data for those 724 species, and B, abundances for those same species, but derived from e-bird observations. So here's another nice example of e-bird being useful to scientists. But if you're like what the heck is an e-bird? Well, I suggest you go listen to episode 33 of this podcast.

It's all about e-bird. Then in this study, there are a few other steps in the process, and we'll just fast forward past those. Just know that the researchers could extrapolate from those 724 bird species to get abundance estimates for almost every other bird species on the planet. a total of 9,700 species for this study. The end result was a pixelated map of the world showing bird density estimates for every pixel. The pixel size was 5 degrees of latitude slash longitude on each side.

So a pretty low-res world map, sort of like the 8-bit graphics in the original Super Mario Brothers. But that's still pretty sweet. making this map is really what the researchers were trying to do. They said, quote, our main objective was to quantify the density of bird species throughout the world. End quote. It took a few more fancy computations to get from data on the map to the final number of 50 billion birds.

I wonder what you think about this estimate for the number of birds on Earth. Is it more than you would guess or less? There's no easy way to confirm that $50 billion is a reasonably accurate estimate. It's the best we have at the moment. But, assuming it is a good estimate, do you think that the world needs even more birds? I sure do. Or are you some kind of sociopath who thinks $50 billion is too many birds? As if it was even possible to have too many birds.

I'll tell you what the world does have too many of. People, that's what. The human population is 7.9 billion right now as I'm recording. But a few days from now, when this episode goes live, they'll probably be like 8.5 billion people. But we're just one species, one ape. But birds, there are between 10 and 11,000 bird species, and they add up to only 50 billion individuals. I'm not sure what to think of all this. It's just interesting. Anyway, this study we're talking about had several other valuable findings. As one example, the data showed that the distribution of abundances across the 9,700 bird species

is skewed. By that, I mean, there's just a handful of super common species, each of which has tons and tons of individual birds. Yes, I'm looking at you, ring-billed gull. but most other species are rare with a relatively small number of individuals per species. All of this information, the results of this study, can be useful in guiding conservation work in birds. For a given country, island, or ecoregion, it would be really helpful to have estimates of not only the number of species, but also the numbers of individuals of each species. Just when you thought we were done here, it's time for the speed round. Speed round.

I'm going to tell you about five more studies from 2021. How exciting, right? But I'm allowing myself only 100 words to describe each of them. Ready? Here we go. You may recall that I did an episode on the use of artificial intelligence in the field of ornithology. Well, a snazzy study published this year in the journal Ornithological Applications involved the use of aerial drones and AI to monitor seabird nesting colonies. The birds were

black-browed albatrosses and southern rockhopper penguins on the Falkland Islands. The researchers flew drones over the breeding colonies and took 10,000 photos. Back in the lab, on the computer, an artificial intelligence algorithm looked at all those photos. The AI identified and counted birds. It was accurate about 90% of the time. 100 words exactly. Bam! Red poles are cute little finches of the far north.

There are three species, all in the genus Acanthus. There's common, lesser, and hoary red pole. They look fairly similar, but there are some physical differences. Well, a study published in Nature Communications suggests that there's really just one red pole species, not three. The researchers analyzed data from the full genomes of 73 individual red poles. They found evidence that the three, quote-unquote, species, freely interbreed. But what's fascinating is that pretty much all of the physical differences we see among the three types are the result of just a handful of genes.

Bam! That is 100 words, baby! There may be fewer species of red poles, but hey, there is an entirely new bird species that was discovered this year. It's the Inti-Tanager, Heliotraupus O'Neely, from the forests of Bolivia and Peru. The Inti-Tanager is a yellow bird with a bold black eyebrow. It's got a bushy crest on its head and a pink bill. Speaking of Bills, people started calling it the Kill Bill Tanager, referring to the yellow and black jumpsuit worn by Uma Thurman's character in the Quentin Tarantino movie Kill Bill. Not only is this a new species, it represents an entirely new genus.

There was another awesome discovery in South America. It turns out that two birds in Patagonia, both tapakullos in the family rhino-cryptody, like to eat Truffles. Truffles are fungi that produce fruit underground. They need animals to dig them up to spread their spores. Well, that's exactly what the Chukau Tapakulo and the black-throated wet-wet do. Researchers analyzed the poop of these little birds and found truffle DNA in there, along with viable spores. This is the first evidence of birds dispersing truffles. The birds are helping the forest because truffles have symbiotic relationship, with many tree species.

Birds use lots of things to line their nests, feathers, lichen, grasses, and hair. A study in the journal Ecology looked at how common it is for birds to steal hair from live mammals. This phenomenon hasn't been well studied, but the authors of this study were able to turn to another trusted source of data,

YouTube! They found 99 videos of birds stealing fur from humans, dogs, raccoons, foxes, and even a porcupine. The thieving bird in most of the videos was the tufted titmouse, Beolophus bicolor. This study also gives us a great new word for stealing hair, kleptotraki. Woo, we did it. We survived the speed round.

We've proven that we can learn about birds at a dangerously fast pace. let's never do that again. Well, at least not till next year. I just want to close out this episode and this year by saying that 2021 was a great year for me and for the Science of Birds podcast. Despite so much craziness out there in the world, it's been comforting to me to sit down again and again

to write that next podcast episode for you. I'm really excited about how things are going, and I'm honored that you guys enjoy what I'm doing here. The number of monthly downloads for the podcast increased fourfold in 2021, from about 3,500 in January to over 14,000 this month, which is December. I love looking at that graph of downloads. I can see how the show is reaching a wider audience over time. That's good to see because I feel like this is a pretty narrowly focused. show, and it's a little offbeat sometimes. It's not for everyone. It's not meant to be for

everyone. But it is for you because you're cool and because you quote unquote get it. I got a lot of encouraging feedback from you guys this year in the form of five-star reviews on Podchaser and Apple Podcasts. And you've reached out to me with kind words via email and Instagram too. Thank you so much for the many, many ways you support me and this show. I started my Patreon page this year and launched the Science of Birds online shop. Both have already been really helpful sources of income for me. They help me pay the bills as I keep busting my tail to give you an educational and, let's be honest, hilariously entertaining podcast. I'm super jazzed about 2022 and I really hope you are too. I've got lots of ideas for how to improve and

grow the podcast in the coming year. I'm also making a personal commitment to develop some good healthy habits, including but not limited to getting up earlier, exercising, meditating, learning Spanish, and being more focused while I work. I won't bore you with the details, but let's just say I'm excited to continue my professional and personal growth in 2022. All of the changes I'm making should make me more productive, too. That means you can count on a continuing, steady flow of geeky podcast episodes about the science of birds.