The Science of Birds - Answers to Your Questions About Birds - Vol 3

Episode Date: May 17, 2023

In this episode—which is Number 76—I’ll be answering some interesting questions sent to me by my listeners. Questions about birds, of course.The questions in today’s episode came from not just any old listeners, but from my supporters on Patreon. At the two higher tiers of support, one perk for my patrons is the chance to send me questions for these “Ask Me Anything” episodes. So if you’d like to ask your own question for a future episode, consider becoming a supporter of this show on Patreon.Support 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 exploration of bird biology for lifelong learners. In this episode, which is number 76, I'll be answering some interesting questions sent to me by my listeners. Questions about birds, I mean. Just to be clear, these aren't random interesting questions like,

can pure reason lead us to understand the ultimate nature of reality? Or which is better, sharks or snakes? No, we're talking about birds today, of course. But in case you're still thinking about those two questions, I'm not so sure about the ultimate nature. of reality, but snakes for sure. Snakes all the way. The questions in today's episode came from not just any old listeners, but from my supporters on Patreon. At the two higher tiers of support, one perk for my patrons is the chance to send me questions for these Ask Me Anything

episodes. So if you'd like to ask your own question for a future episode, consider becoming a supporter of this show on Patreon. All right, let's jump right in. Our first question comes from Jamie. Here it is. Quote, Why do some bird's eyes change color as they age? For example, the osprey, my favorite bird.

End quote. Excellent question. Jamie? The osprey, Pandian Halliades, is a great choice for your favorite bird. And this species is a great example of how eye color can change with age in birds. Juvenile ospreys have darker eyes than adults. Juvenile irises are reddish orange or even kind of brownish. But adults have yellow irises that give their eyes a piercing appearance. As I understand, the transition from orange orange or brown to yellow eyes happens within the first year of an Osprey's life. Many other bird species show a similar change in eye color between age classes, between juvenile

and adult birds. Just to name a few examples, we have blue-footed boobies, ring-billed gulls, bald eagles, sharp-shinned, and Cooper's hawks, brown thrashers, and brewers blackbirds. There are also eye-color differences between males and females, right? Like with Brewer's Blackbird that I just mentioned. Males have bright, yellowish-white irises, and females generally have dark eyes. The opposite is true in bush tits. Now, in case you aren't familiar with the bush tit, sultraparis minimus, this is a cute gray songbird that lives in western North America.

It's actually the only species on this continent representing the long-tailed tit family, egyptalidae. The rest of the species in this family are found in Europe and Asia. Anyway, female bush tits are the ones with the pale irises and males have dark irises. In many populations of this species, the sexes are more or less identical in every other way, so it's fun to be able to tell males and females apart by looking at their eye color. So we have eye color differences between age classes and between the sexes, but we're not done. Because in some species, the eye color of an individual bird can change from one season to the next, and then back again. For example, in the brown pelican, iris color is brown in adults during the

non-breeding season. But when it comes time for courtship, their eyes turn whiteish or pale blue. Later in the season, when the eggs are laid and incubation begins, the eyes of adult brown pelicans go back to being brown. Jamie's question was about why eye color changes in birds. Well, the best explanation for why juveniles and adults of the same species have different eye colors is that it helps the birds figure out who is or isn't old enough to mate. birds are driven to find mates and crank out some babies but time and energy are limited an adult bird doesn't want to waste its time and energy trying to woo to court an unreceptive and or immature bird that isn't going to go anywhere so eye color can be a helpful signal an indicator of whether a bird is capable of making some baby birds it's an adaptation at least that's our best high hypothesis to explain what's going on. Similarly, we can understand eye color differences between males and females as adaptations for signaling. And the way eye color changes during the early

breeding season in birds like the brown pelican? Yep, same idea. This is a signal of reproductive condition. So let's say you're an osprey on the lookout for a potential mate. And you're at a yoga class or the public library, or wherever it is that Osprey's like to hang out. I don't know. Anyway, you're looking around, scanning the room, then you see another bird and think, Hello, what have we here? What if I just...

Wait, are those reddish-orange eyes? Dang it! It's a juvenile. You end up saving yourself some time and maybe some embarrassment by moving on to more soon. prospects. The next next question comes from Roy, and it has to do with bird evolution and paleontology.

Paraphrasing Roy a bit, here's his question. Quote, what birds, aka avian dinosaurs, survived the KT extinction event, and do they have fairly direct ancestors still alive today? For example, we know that there were, quote-unquote, ducks in the Cretaceous period, and we have ducks now. Are today's ducks directly descended from those prehistoric ducks, or is it just convergent evolution? I've also read that ratites first evolved in the Cretaceous period. So I assume today's ratites are direct descendants of those birds from millions of years ago. Surviving the KT event was a pretty small window of opportunity for certain species,

and I think it's fascinating to think about how only a few made it and then branched off to eventually become today's birds. I would like to learn more about which birds survived. End quote. Okay, first off, brilliant question, Roy, but there's a lot to unpack there. At the heart of this question is one event, the great extinction that occurred 66, million years ago when an asteroid slammed into the earth. That, of course, wiped out all the dinosaurs. Now, you can't see it, but there was an asterisk at the end of that last sentence. All the dinosaurs, asterisk, except for the birds, because birds are dinosaurs. Scientists have several names for that big extinction event. In geological terms, this event marks the dividing

line between the Cretaceous period and the tertiary period. Roy used the name KT extinction. KT is shorthand for Cretaceous dash tertiary, even though Cretaceous is spelled with a C, and it seems tertiary is now an obsolete term. Anywho, don't let me drag you any further into the weeds with this jargon. Toward the end of the age of dinosaurs, in the final few million years of the Cretaceous period of the Mesozoic era, birds were flapping around all over the place. The little darlings were already diverse and complex by that time. In fact, there's even a field guide to birds of the Mesozoic. I've got it right here. It's a really cool book with tons of fascinating illustrations. I'll put a link to it in the show notes. We know from fossil evidence

that at least some birds in the Cretaceous had colorful, elaborate plumage, and many of them were certainly strong flyers. Birds, in the broad sense, had split into two major evolutionary lineages by the end of the Cretaceous. First, there were the Anantiornathes. This name means opposite birds. This was the more diverse and abundant of the two major lineages. Anantyornathies would probably have looked a lot like birds to us, at least superficially. But if you picked one up and pried open its tiny mouth, you'd most likely find rows of pointy teeth in there.

You'd most likely get a nasty bite on your finger too, but serves you right, I guess, for grabbing the little beast so rudely. Anyway, most enantiornathies had teeth, and most of them also had fingers with claws on their wings. Sadly, the entire lineage of an antioanathies went extinct 66 million years ago as a result of the asteroid impact. Adios, little amigos. The second major lineage of birds was the eurnathies, which translates as true birds. As you might guess, this is the lineage that included the ancestors of all the birds alive today. It seems some side branches of the eauanathies lineage went, extinct alongside the antionathies and the non-avian dinosaurs like T-Rex.

But a few members of the Eurnathies group survived, and this gets us closer to what Roy was curious about. Among the eunathies that made it to the other side of the terrible extinction event was the ancestor of today's Paleognath birds, the ostriches, Rias, cassowaries, emus, and Kiwis. These are the flightless ratites, Roy referred to in his question. Ratites, together with the tinamus of South America, which can fly, form the group Paleognathy. Scientists have yet to discover the fossils of any ancestral Paleognath birds from before the KT extinction. But maybe some fossils will turn up eventually. Who knows? But looking at the fossils of other ancient birds and at evolutionary changes inferred from DNA data,

it's pretty safe to assume that paleognaths were cruising around on the planet well before 66 million years ago. The first paleognath fossils we do have were from small birds that could fly. Those fossils are from the early Cenozoic era, well after the non-avian dinosaurs all went extinct. So all the flightlessness we see today in ostriches, cassowaries, Kiwis, and whatnot. That all happened millions of years after the big extinction. The story of Paleignath evolution and flightlessness is fascinating, but that will have to wait for

another podcast episode. So there's one lineage that survived, Paleognathy. Paliagnathy? That's how I want to say it. Paleignathy. But I think that paleognathy is the correct pronunciation. Another lineage of birds that made it across the dreadful threshold of the extinction event was Galloanseri. There are definitely fossils of these birds from both before and after the extinction. The word galloanseri combines the Latin word for rooster, gallus, with the word for goose, answer. We call all the birds belonging to this group today foul. So these birds from about 66 million years ago, let's call them rooster geese, actually represent the common ancestors of today's chickens, pheasants, quail, ducks, and geese.

Way back at that time, there were no species that we would recognize as full-blown ducks or pheasants or whatever. Sure, the ancestral rooster goose is sometimes described as duck-like by scientists, but actual ducks evolved only millions of years later. They traced their ancestry back to those gallo-anserens that survived the extinction event. Okay, are you following so far? We've got paleognathy as one lineage that survived, and we've got gallo-ansary as another. Several lines of reasoning tell us that a third bird lineage must also have survived the asteroid, and that was Neo-Avees, as in the new birds, right? Neo-Avies was the lineage that eventually diversified and split into all the other modern birds.

But what the ancestral Neo-Avies birds looked like around the time of the KT extinction is unclear. Fossils for those birds have yet to be discovered. So, yes, all modern birds are directly descended from these few lineage. that managed to endure through the worldwide catastrophe that swept the Earth 66 million years ago. But I don't think we can say that any of the ancestral birds from that time would be recognizable as, say, a duck or an ostrich or a sparrow. A lot of geologic time has passed since then and a lot of evolutionary change. As another interesting piece of this story, some scientists suggest that all, All or most of the birds that survived were either ground-dwelling birds or water birds.

In other words, they were not forest dwellers. Birds that depended on trees for nesting and finding food suffered heavily because the asteroid impact and its aftermath wiped out forests across the planet for hundreds or even thousands of years. In the first 10 million years after the big extinction, birds went through some rapid and dramatic evolution. Many of the avian groups that are familiar to us today with their wildly different shapes and lifestyles came into being back in the early Cenozoic, not long after the extinction event that obliterated all other birds and the non-avian dinosaurs.

I hope my answer to that last question made sense. It was a bit tricky to explain all that terminology and still try to be concise. And believe it or not, it gets way more complicated than what I just presented. The next question is, by comparison, much more down to earth. It comes from my supporter, Dan. He said, and I'll paraphrase here, quote, I love our bird bath. It was there for decades before we moved in, and it appears to be a known spa for many birds, as it gets used a lot. That said, I've noticed that it's almost always a subset

of the usual residence. The dark-eyed junkos, spotted tohies, American Robins, and song sparrows use the bird bath constantly. But we have other very common residents that we see around all the time that we never see in the bath. Northern Flickr, Brown Creeper, and Stellars J, for example. So it makes me wonder, do birds have different bathing needs? And if so, why? End quote. That's an interesting observation and question, Dan. Ornithologists have figured out that bathing behaviors differ from one bird family to another, and sometimes from one species to another. But the behaviors we're talking about are what the bird does when it chooses to take a bath and get wet. From what I could find, there isn't much information in the scientific literature on how the actual

need to bathe differs among species. Like, do American robins need to take baths more often than northern flickers for some reason? But Dan's observation that some species appear to bathe more or less frequently, has been made before in other regions. For example, there was an article from 2006 in the publication British Birds. In a single 12-month period, data was collected from all birds visiting a pair of bird baths. There ended up being 6,309 visits made by 30 species. It turned out that three species, the Eurasian blackbird, Eurasian blue tit, and greenfinch accounted for about 62% of all the visits to the baths, and some of the 30 species in this study almost never visited the baths.

Side note here, it's important to keep in mind that birds visit bird baths to both bathe and to drink. So we're kind of talking about two distinct behaviors here. In any case, what wasn't clear to me from that 2006 article in British Birds was whether the bird species that visited the bird baths most often also happened to be the most abundant species in the area. For example, if you've got a gazillion blackbirds fluttering around in your garden every day, you might expect that species to show up a lot at your bird bath over the course of a year. Likewise, if a green woodpecker shows up only three times a year, you're not going to have that species splashing around in your bird bath more than a few times. Dan pointed out in his question that he believes some of the more abundant bird species in his

yard are not using the bird bath very often. So his hypothesis is that visitation to his bird bath across the species is not simply proportional to the relative abundances of bird species. See, this is where we could take that hypothesis and do some science on Dan's backyard birds. First, we'd want to conduct an unbiased survey of the species on his property to figure out their relative abundances.

Then we'd need to do another rigorous survey of which species are visiting the bird bath. Finally, we'd have to sit down at a computer and run some statistics. Only then could we really figure out if Dan's hypothesis holds any water. But even if we went through all that trouble, it still wouldn't answer the actual question Dan was asking. And I don't have an answer.

It seems scientists haven't yet described the different bathing needs of birds, if there are any differences. And it turns out that ornithologists aren't even 100% sure why birds take baths at all. It probably has to do with feather maintenance. But how exactly? Does jostling your little body around in a puddle really get much grime off your feathers? Or does the water realign the barbs on the feathers or knock parasites off? Or what? The last thought I have about this is that birds certainly differ in their behavior when it comes to predator avoidance. Some bird species are more wary, more skiddish around other birds or other animals, probably because they're more

vulnerable in one way or another. I know that northern flickers, for example, are especially nervous birds that take off at the slightest move from a nearby human. A bird that soaks itself in a bird bath is making itself potentially more vulnerable to predators, because they're out in the open, visible to predators. And wet feathers can make flying and therefore escape more difficult. So maybe some bird species don't take baths that often because they have an instinctual reluctance to make themselves vulnerable. Maybe they find other safer ways to get clean and to drink. Or those birds are just thirsty, filthy, and stinky all the time. They're shunned by members of polite society, including their closest friends. I say it would be better to risk your life at the

bird bath, because to be shunned by polite society is a fate worse than death. Our next question has to do with bird conservation. My listener, Allie, lives in Australia, and she had this question. And once again, I'm paraphrasing. Quote, I wonder if there are any other conservation programs in other parts of the world. Like I know in New Zealand, they have dedicated islands for the rehabilitation of the Kakapo. I'd love to know about similar programs around the world that try to reverse human impacts. End quote.

Thanks for this question, Allie, and oh boy, yes, there are many, many bird conservation programs around the world. The ones I can think of off the top of my head would only scratch the surface. Many of these programs are small, local efforts, but many others are enormous projects with dozens or hundreds of people involved, maybe thousands. Some programs were spearheaded by a single, passionate person. Others are being coordinated by multinational conservation organizations and or government agencies. Just that fact alone warms the heart, doesn't it? The fact that many thousands of humans on this planet, as you listen to this podcast right now, are putting their valuable time and energy into the protection and conservation of birds.

There is so much negative news coming at us from all angles every day. We just got to stop and appreciate the goodness of people sometimes. So to those of you listening right now who have helped birds and their habitats, thank you. You are truly awesome. Okay, I'll just wipe away that single tear, compose myself, and get on with the show. A few North American bird species I can think of that have their own major conservation programs are the California Condor, the Northern Spotted Owl, which is a local celebrity where I live, and Kurtland's Warbler. And there's the red cockated woodpecker, greater sage grouse,

whooping crane, piping plover, Florida scrub jay. The list goes on and on. It's great that there are conservation programs for these species. But at the same time, it sucks that these birds are in so much trouble that they need conservation in the first place. We could come up with a mile-long list of other bird species from around the world. Instead of doing that, I'll tell you a little about a single, amazing conservation program in French Polynesia. I chose this one because Ali mentioned the special islands used for conservation in New Zealand. Birds and other wildlife on islands are generally super vulnerable to human mischief, especially to the ravages of the animals we introduce, like rats, goats, dogs, pigs, snakes, et cetera.

Hardcore conservationists in New Zealand have been able to eradicate all the non-native predators on some small islands. Once those alien species are all weeded out, it's at least possible for the native birds, other critters, and plants to recover on what are now predator-free islands. So, French Polynesia, way out in the middle of the Pacific Ocean, about 1,000 miles or 1,600 kilometers from Tahiti, there are two groups of small islands, the Actione Archipelago and the Gambier Archipelago. These islands are home to several bird species that are incredibly rare, the critically endangered Polynesian ground dove, the endangered Polynesian storm petrol and the endangered Tuomotu sandpiper. I actually talked at length about this sandpiper in the podcast episode I did a while

back on the family Skolopaceti, the Sandpiper family. In 2015, three conservation organizations got together to undertake a massive project. BirdLife International, S.O.P. Manu and Island Conservation were the three organizations that visited six islands and spent months clearing them of four invasive mammal species, the Pacific Rat, Ship Rat, Feral Cat, and Rabbit. The operation involved 31 people from six countries. Their work required several ships and 165 hours of helicopter flights.

This was one of the largest conservation programs of its kind in the Pacific region. Two years after the initial effort, the team returned to do some surveys of the islands. They confirmed that five of the six islands remained completely free of rats, cats, rabbits, and, to the team's surprise, ghosts. They couldn't find a single ghost. Reading the islands of ghosts hadn't been one of the project goals, but hey, bonus! I'm just kidding, of course. I'm sure those islands are still swarming with spooky ghosts.

But no rats, cats, or rabbits. This project cleared about 3,000 acres. or 1,200 hectares of habitat and made it available for our endangered island birds. The Polynesian ground dove has since spread from just one island to the other restored islands. Further surveys in 2020 revealed that these and several other bird species are recovering nicely. So for now, this story has a happy ending. BirdLife International, S.O.P. Manu and Island Conservation, with the help of the French Polynesia, government and local people have done an amazing thing with this program. It's going to take

their continual vigilance to make sure the islands don't get reinvated by rats or rabbits or whatever in the years to come. But for now, there's a lot more hope for the survival of the Polynesian ground dove, Tuomotu Sandpiper, Polynesian storm petrel, and a host of seabirds that nest on the islands. And speaking of seabirds, our last question today is from Sarah. She asks, quote, Can you talk about how some birds like gulls are able to drink salt water? Do they deal with this problem the same way that marine mammals like seals do? End quote. Cool, this is good stuff. Sarah's question is about physiology, specifically osmo regulation. Osmo regulation is how

an animal maintains the proper balance of water and salt in its body fluids. First off, let's talk about why drinking salt water might be bad. For humans, a little bit of salt water here and there is probably fine. I mean, don't quote me on that because I'm not a medical doctor. But who doesn't like a Bloody Mary now and then, right? Problems occur when we drink a lot of salt water. If our cells are subjected to too much salt, we can die. Our kidneys work to get rid of excess salt, but they can only do so much.

If you go around chugging seawater like a crazy person, you're going to end up peeing a lot. That's because urine is produced by the kidneys. But no matter how much you make pee-pee, your body won't be able to get rid of the salt fast enough. You're going to get dehydrated and you're going to die, son. That's why it's sadly ironic that a person without fresh water could die while adrift on the ocean. Water, water everywhere, nor any drop to drink, as the line goes from the rhyme of the ancient mariner. So how about marine mammals like seals, as Sarah mentioned in her question? Why don't they die from salt overdose?

They must swallow gallons of seawater every day. Actually, not so much. It seems most marine mammals don't really drink water at all. They can survive happily on only the water they get from the flesh of their prey and from some water produced in their cells by metabolism. The fish that a seal might eat is only about as salty as the blood of the seal itself. So there's no excess of salt being swallowed. Now, that said, some marine mammals may have some marine mammals may have some,

specialized kidneys for getting rid of excess salt. And for some of them, scientists still don't know a whole lot about how they deal with salt. But that's okay because nobody really cares about all those dumb old mammals anyway. Birds, on the other hand, are the best. They might even be better than snakes. Birds can get rid of salts using their kidneys, similar to what mammals do. However, birds have another trick up their sleeves. Or I guess I should say another trick up on top of their eyes? Because many birds, especially those that live in marine environments, have a big salt gland located in a bony depression just above each eye. This salt gland is also called the supraorbital gland. Supraorbital means above the orbit, and orbit is the technical

name for the eye socket. This pair of glands filters the bird's body fluids, then concentrates the removed salts, and excretes them as a clear, salty liquid from tubes that empty into the nostrils. That's why if you watch gulls on a beach or some other seabirds, you're likely to see a bird with a droplet of clear liquid hanging from the end of its bill. Once the droplet gets big enough, the bird might shake its head to fling the salty solution away. This whole scene might look like the bird has a runny nose and then it sneezes. But nope, it's just the salt glands working their magic. In some birds, these glands can, apparently, remove ten times more salt from the blood than the kidneys. Birds that have very active supranorbital glands include

penguins, albatrosses, ox, sea ducks, pelicans, gulls, cormorants, shorebirds, some herons, and other ocean-loving characters of that nature. Many of these birds can straight up drink seawater, and they can also eat prey animals that, unlike most fish, are super salty. The flesh of marine invertebrates like crabs and squid are about as salty as seawater. One challenge is that pumping salts from the blood into the cells of the superorbital glands burns a lot of energy. And birds are all about conserving energy. So they have a great adaptation that allows them to deactivate their salt glands when they don't actually need them. This sort of thing happens in birds that spend part of their year in freshwater and the rest of the year on the

ocean. We're talking birds like loons, some ducks, gulls, maybe some cormorants. The salt glands of such a bird become active only after the bird starts drinking seawater or eating super salty prey, which makes me wonder what happens when gulls eat salty french fries in a parking lot. Hmm, sounds like a research project waiting to happen. This ability to shrink and grow your salt glands is yet another super cool avian superpower. So for birds that live on the ocean, they're like, the ancient mariner can stuff it.

Water, water everywhere, and we can drink that salty stuff all day long to our little heart's content. Thank you to Jamie, Roy, Dan, Ali, and Sarah for the excellent questions. It was fun working on the answers for you, and for everyone listening. We'll do it again sometime.

If you're not yet a supporter of this show and you'd like the chance to contribute questions for a future podcast episode, have a look at my Patreon page. Just go to patreon.com slash science of birds. My newest patrons are Jeff Giddings, John Hanley, and Morgan and Jess Katrin. Welcome and thank you very much.

I really appreciate the support. Now, very quickly, I want to address an error I made in the last episode. That was episode 75, which was all about the Shrike family, Laniety. I told you that people in Germany called the Great Grey Shrike, the Nine Murder. I went on to make jokes about this a couple times, because how could I not? Well, several real-life German people, listeners of this podcast, emailed me and told me that there is a Shrike they call Nine Murder. but it's actually the red-backed Shrike, not the Great Grey Shrike.

So I'm sorry for the mistake, and thank you to my very kind listeners in Germany who corrected me. If you would like the opportunity to correct one of my many errors, you can always send me an email. Just kidding, I like to think I don't make too many errors on this show. I do my research, and I try really hard to give you guys just the facts. But hey, I'm only human. Anyway, my email address is Ivan at Scienceofbirds.com. As always, you'll find the show notes for this episode, which is number 76, on the Science of Birds website, scienceofbirds.com. I'm Ivan Philipson, and I hope you are having a lovely day. Peace.