*Mickenzee and Carolyn at Lincoln Elementary (photo by Mickenzee Okon)*

In this episode, we answer questions like "why do robins lay blue eggs?" and learn about precocial and altricial young with our egg expert (egg-spert if you will) Carolyn Byers the Education Director at Southern Wisconsin Bird Alliance.

⁠See Carolyn's nest research on our Into the Nest page!⁠

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Transcription

Hey, and welcome to Questions Asked by Curious Kids or QuACK, a podcast made by Southern Wisconsin Bird Alliance. This is a podcast where we gather questions about nature from kids to be answered with a local expert. My name is Mickenzee. I'm an educator and I'll be the host for this series. And this is a very special episode where I'm back with Carolyn Byers, my coworker and the education director here at Southern Wisconsin Bird Alliance, and she's going to answer all of our questions about eggs. All right, let's jump in with Carolyn.

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Mickenzee: Hey, Carolyn, and welcome back to the show.

Carolyn: Thanks. Thanks for having me. It's so fun to be here.

Mickenzee: Okay, so last time when you were on the show, you told us about nests and all about your education work at Southern Wisconsin Bird Alliance. And it's so fitting that you could come back to teach us about eggs.Before we get started with the questions from the kids, could you tell us about what about eggs sparks your interests? And why do you like them so much?

Carolyn: Oh, Mickenzee, I could talk for hours about this, but we don't have hours, right? We can't.

Mickenzee:I mean, we could do an extended cut.

Carolyn: Okay, cool. Yeah, I think, I mean, eggs are gorgeous, and most of the eggs that I've worked with are really small, and so they're, like tiny little secrets hiding out in grasslands. So like, part of the reason I love them is because they're so special to find, like they're hidden, you know, purposefully. The momma birds don't want you to find them. And so then it's just like this precious secret that's going to become something amazing. And I love that.

Mickenzee: That is a really beautiful description. That's poetic. Oh my goodness. All of our questions today were submitted by the third graders at Lincoln Elementary School here in Madison. And our first question today is how many eggs on average does a swan lay? And more broadly, why do different birds lay different numbers of eggs?

Carolyn: I love that they're thinking so closely about swans. This is fun. Yes. So there are three types of swans in Wisconsin. We've got mute and trumpeter and tundra okay. And trumpeter and tundra. They all lay a different number sort of. But most of them lay not so many eggs. If we're thinking about birds in general, they lay on the fewer side of eggs. Okay. So Trumpeter Swans can lay between 2 and 9. Tundra Swans can lay between 4 and 5. They have a really you know, they're pretty particular about their number of eggs. And then Mute Swans is between 4 and 8. So, you know, not too many. And you asked why birds lay a particular number of eggs, right? Okay. So each different species of bird has a different kind of life, right? They live differently. They have different body shape and size. They have a different habitat. They have different things that they eat. And so the way they raise their young can also be different. And so some birds lay only one egg or maybe 1 or 2 eggs, and they put all of their energy into that egg, into that chick. They usually lay really large eggs compared to their body size. So I'm thinking of like, oh, some birds called Murres or Razorbills. They usually lay one, maybe two eggs and they're really, really big compared to their body. Or like, oh my gosh, what is a Kiwi? Have you ever seen a picture of a diagram of how big the egg is inside of a kiwi before it's laid? Huge. Huge. I don't want to be a momma Kiwi, but so there are some birds that they make really, really large eggs. When the chicks hatch, they're really big. They have their eyes open. They usually have downy feathers that are able to help keep them warm. They're a little bit more developed. Okay. Then there's other birds that lay many eggs and those birds, usually the eggs are smaller compared to the adult body. So they're trying to maybe not put all their eggs in one basket. So, you know, if a predator gets 1 or 2 of their eggs or if a few don't hatch, it's not a big deal because they laid a lot. So a turkey can lay like 14 eggs.

Mickenzee: Whoa.

Carolyn: That’s a lot of eggs right? And then of course, there's everything in between. So that's about the number of eggs right. Do you want to talk about precocial and altricial? Do we have time for that?

Mickenzee: Yeah. Those are some cool science words I'd love to talk more about.

*Killdeer Chicks are precocial (photo by USFWS)*

*Robin Chicks are altricial (photo by USFWS)*

Carolyn: They’re some of my favorites. Okay. So precocial usually means, like, if we're talking about people. Right? Precocious means that you develop earlier than your peers. Say, other kids your age. So if you're precocious or maybe you crawled before most kids do, or maybe you walked before most kids do. Or maybe you said way more words than most kids do at that age. But a precocial bird, they're usually born with their eyes open. They can maybe walk, walk away from the nest like within a day of hatching. You know, they usually just follow mom around and watch what she eats, and they're like, oh, I'll try that too. And so it's a lot easier for parents to raise precocial chicks because they basically just follow a mom around. So a bird that has precocial chicks, usually they can have more chicks because it's not as much work to take care of each chick. But they usually take a lot longer to hatch because they have to be very well developed before they hatch out of their eggs. So it's kind of a trade off.

Mickenzee: Yeah.

Carolyn: But then on the other end of the spectrum, we have altricial chicks. And those ones, when they're born, their eyes are closed. They have no feathers on their body. They can't keep themselves warm or cool. They can't feed themselves. They just open their mouths and parents put food in and they eat it. And so those chicks, they usually, take longer from when they hatch to when they're ready to leave the nest. And it depends on the species for how long that is. So the parents have a lot of work to do to get them ready to leave the nest after they've hatched.

They have to feed them like every 3 to 5 minutes, sometimes depending on the species.

Mickenzee: Those are busy parents,

Carolyn: That’s a lot of work. Yeah. So it's a trade off and they usually aren't able to have as many chicks because it's so much work. Yeah. So you know, these birds aren't thinking to themselves, gosh, should I have precocial or altricial chicks this year? I don't know, you know, they're not really thinking about that trade off. It's more of an evolution thing that, you know, their species is locked into doing this, this type of child raising.

Mickenzee: Yeah. So a specific type of bird will have one or another species might have the other. They don't get to pick.

Carolyn: Yeah. And it's not just the two extremes of precocial and altricial. It's all like a gradient. So there can be semi-precocial chicks or, you know, everything in between that it's really cool.

Mickenzee: That is really cool. All right. And for our next question, this question asker wonders: Why are robin's eggs blue? And in general, why do birds lay different colored eggs?

Carolyn: I love this question. I want to hang out with these kids.

Mickenzee: These are really good questions.

Carolyn: So okay, I will admit I needed to do some research to figure out specifically robin's eggs so I can talk about them for a second. In a second. But I know that bird eggs are different colors for different reasons, so I know that, for example, a lot of birds have speckled eggs like eggs with little spots on them, and often they're brown or gray.

*Camouflaged Killdeer eggs (photo by USFWS)*

And those eggs are really good for camouflage. So it makes it much harder to see the eggs so that any predator that's just walking around looking for food, it'd be really hard for them to see them. So much so that like, you know, Killdeer? They're little birds, they often lay their eggs near parking lots or if there's gravel or something or rocks, they put their eggs right on the rocks. And even if you know where a nest is, like, say, somebody pointing to it, they're like, ‘the nest is right there.’ It takes you a little while before your eyes and your brain can connect and figure out that it's actually an egg, because they're so well camouflaged.

Mickenzee: Totally. Yes.

Carolyn: So some eggs are colored for camouflage. Okay. There's a whole bunch of other eggs that are just white, which is not camouflage in nature, it stands out. But a lot of those nests are like woodpeckers and they are cavity nesters. They nest in holes in trees. So it doesn't really matter if the egg is camouflaged. They're really well hidden, just super cool. So scientists actually were really confused about these blue robin's eggs. They're like, what is this? And they did this whole research study where they were testing why certain eggs were blue, and they found this one species of bird. And I'm forgetting what it is that species can lay eggs that are a lot of different colors. They can lay them white, they can lay them olive green, they can lay them blue. And so they had this really cool study set where they could check all these different egg colors that were made by the same species of bird for all these different variables. It’s really cool.

Mickenzee: Woah.

Carolyn: So the scientists learned that egg shells protect well, they protect the baby inside, of course, and they protect it from UV rays from the sun. They also help keep the egg warm or cool, depending. And so it turns out like, have you ever been in a hot car, Mickenzee?

Mickenzee: I've definitely been in a hot car.

Carolyn: Yeah. So, And have you ever, like, thought about what color clothing to wear, depending on how hot the day was? Yeah. So darker colors absorb more heat, and they keep the inside, whatever’s inside of it warmer, and lighter colors don't do that. So if it's a really hot day out, you know, you don't want to be inside of a black car. Maybe you want to be inside of a white car, or maybe you want to wear your white clothes, not your dark purple clothes, you know?

Mickenzee: Yeah.

Carolyn: So apparently the scientists found out that blue is a really good balance. It is enough color that it protects the baby inside from UV rays, from the sun, but it's not so much color that the eggs overheat.

Mickenzee: That is really cool.

Carolyn: Awesome balance. I love it and it's gorgeous.

Mickenzee: Yeah, yeah, and it's so fun to see. Wow, that's so exciting. Carolyn, I feel like every time I'm around you, I learn so much. Thank you to the Lincoln third graders for submitting your big questions. And thank you, Carolyn, for coming back on to teach us.

Carolyn: Anytime.

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If you are interested in learning more about bird eggs or anything else nature related, please head to our website as to swibirds.org and click on over to the education tab, where we've completely revamped the web page, to showcase our free lessons, games and activities. You can find things like All About Nests or Build a Nest.

You can also check out Carolyn's thesis work in our Into the Nest web page, where you can look under the grasses and see the world of grassland nesting birds. Super cool videos and pictures. It's so fun to explore! If you're looking to get outdoors with us, please check out our events calendar to see if there's any field trips coming up that you want to register for.

If you have a big nature question that you would like to have answered, please have a teacher or grownup submit your question to info@swibirds.org with the title Questions for QuACK. Make sure to include your grade and the school that you attend so I can give you a shout out on the show. Thanks for tuning in and I hope you join us next time on QuACK.

Check out SoWBA’s free lessons, games, and activities!⁠

⁠Get out and explore nature with us!

Make a donation to Southern Wisconsin Bird Alliance

Audio Editing and Transcription by Mickenzee Okon

Logo design by Carolyn Byers and Kaitlin Svabek

Music: “The Forest and the Trees” by Kevin MacLeod