Fatu Badiane Markey 0:15
What can you do with your love of science? We'll tell you!
Hello, everyone and welcome back to the show We Love Science. My name is Fatu
Shekerah Primus 0:46
and I'm Shekerah and today we're talking about how bird
eggs get their color.
Fatu Badiane Markey 0:52
It's going to be egg-cellent!
I'm just gonna add this disclaimer, there will be puns so you don't want them you have been warned. Before we get started, how are you doing Shekerah?
Shekerah Primus 1:14
Um, I'm okay. I'm feeling a little, a little slow today but otherwise I'm okay.
How are you?
Fatu Badiane Markey 1:21
I'm doing pretty good. I'm doing pretty good. Yeah, I think I'm also in the same boat; like today has just been dragging. I don't know what's going on. But it's just been, it's been a little, a little bit of a slow day. So what today we're focusing on bird eggs and how they get there interesting colors including chicken eggs, which have a slightly different color story from other birds. And since we always start with food talk, what is your favorite egg dish or way to eat eggs Shekerah?
Shekerah Primus 1:55
I like that a color story. Um, so when it comes to eggs, I'm
Fatu Badiane Markey 2:00
pretty simple.
Shekerah Primus 2:01
I guess; I don't get too crazy. I like scrambled eggs usually. Sometimes I mixed in veggies. But yeah, like peppers, carrots. Yeah. But yeah, pretty simple scrambled eggs. But Starbucks has these really delicious egg bite things. I think they are literally called egg bites. Like there's like these little egg like I guess cupcake type of things or muffins, whatever you want to call them with the different things mixed in. So there's one with peppers in it of course and I like that one.
I think mushrooms and kale; there's one with bacon and some other yummy stuff. So yeah, I really liked those Starbucks egg bites. Yeah, how about you?
Fatu Badiane Markey 2:59
So I do agree with you that I think I also tend to go pretty simple on my eggs. I do like a very good scrambled egg so like, you know like when it's like really like nice and soft I think is like really nice and not too hard. And I love a perfect like soft boiled like jammy egg. That's like a top for me; that just like makes my whole day. Have the yolk a little bit running just a little bit. It's like it's perfect. I love that. So, let's get into things Shekerah.
Shekerah Primus 3:34
Talking about bird eggs, and their color today; so you did all this awesome research. I can't wait to hear all about it. So tell us how do birds get their color? Sounds like a pretty straightforward question, but I feel pretty certain it's not so straightforward.
Fatu Badiane Markey 3:52
What did you learn? Yeah, so long story short, scientists don't exactly know but they have several ideas.
Shekerah Primus 4:01
Shocker! It's not an easy answer. We're so surprised. I'm being sarcastic here. So what are some of the hypotheses that scientists have?
Fatu Badiane Markey 4:15
So birds are the only vertebrates that lay colored eggs which is something that I found really fascinating. So when you think of I guess like reptiles, you know, their eggs are all white. They don't do colored eggs, which is really interesting. And so it's still not very clear why but I just have a few ideas. So the first one is that this color or pigmentation helps for egg survival in the wild. So if we think about things like protection against the environment, so one example was like protection against rain and temperatures specifically; where dark eggs will heat up faster and hold temp longer and so that helps you know as the like, baby bird or the little chick is developing right because it has to be a certain temperature. Yeah, color can also help camouflage eggs in the environment for predators. I think that's pretty obvious, like positive. There's also this idea that colorful eggs might indicate how fit a female bird is and attractiveness for mating. And one example was given with I think it's like, is it Blue Jays or blue birds that lay blue eggs. And so that color, I guess basically just over time, you know, like the female birds with the nicest eggs are ones that are always chosen for reproduction. So the color just stayed around.
Shekerah Primus 5:48
Women are all, enough, no matter where, what species we're just always being like judged.
Fatu Badiane Markey 5:55
And being extra--blue. It's like come on. And then this one I found really interesting that also goes along with sort of like this idea of how the color of the eggshell can help regulate temperature. But there's also this idea that maybe antimicrobial resistance is better in darker eggs because they can hold heat longer. So then that's gonna, you know, prevent bacteria and like maybe other parasites from growing on the eggs and you know, possibly killing the developing chick. Yeah, and so yeah, lots of ideas. No one is really sure why but one thing scientists do know is that a color co evolved with what we call open nest building birds. So basically, birds when like way back when when they weren't building their nests back in the day, they used to be covered or sort of closed nests, that makes me think of, you know, how like, reptiles will bury eggs, you know, like, like turtles like in the sand. So they would build or basically, you know, cover the egg somehow. And in that case, eggs would tend to be white or brown. And then later on, different sort of like colors started to appear as the way that birds built their nests have evolved. So leaving, and this kind of makes sense with some of the other hypotheses, because leaving nests you know, they're like out in the open, that leaves the eggs vulnerable to predators. So adding color at some point may have proved as an evolutionary advantage. So keeping eggs at a consistent temperature now that they are open to the environment, camouflage and even as a way to maybe distinguish sort of like imposter eggs; because you do have birds who will lay their eggs in other birds nests and then have like that bird raise it's young. There's this one type of bird called a parasitic cockatoo that does that and I was like whoa. So yeah, so lots of stories, I guess lots of hypotheses, lots of ideas. And we're still trying to figure out exactly how and why this happens.
Shekerah Primus 8:12
Yeah, that parasitic
cockatoo. That's, that's a lesson in how not to parent.
Let me just drop my egg here and I'll just, you know fly off, and let someone else do the hard work.
I'm gonna just like stealthily add my kids to yours, you'll believe its yours. Oh Lord, okay, so this is so so so cool. So most of these different theories and hypotheses that scientists have come up with and are researching, I would not have guessed the only one I think I would have guessed is the one about camouflage, right. So you'd have I know that that's something that animals do. So you know, you'd have make eggs a certain color to camouflage it because they're very vulnerable, obviously, at that stage, so you want to be able to protect them as much as possible. But all of this other stuff is so cool. Yeah. So I love that thing. Yeah. And I love that, you know, researchers, it's like, you're so curious about this, they study anything. Anything so curious about how birds, bird eggs, get their colors? Your lifelong passion your lifelong study this is your work, so you never know what you could find. It's true. Yeah, I love that. Yeah. So tell us about the researchers who are actually studying this to try and figure it out.
Fatu Badiane Markey 9:47
Yeah. So
um, I read a recent study from Daniel Hanley of Long Island University, and he recently published in the journal Nature, Ecology and Evolution. And him and his colleagues they did this like really extensive study, where they analyze the color and brightness of one egg from each of 634 species of birds from around the globe.
Right Yeah, wow.
They also correlated this with the breeding range for each species. So this is like, super in depth, right. And basically, what they found is that darker eggs tend to be more common in regions with lower solar density, which means cooler places basically and then eggs that are generally brighter, were found in areas with higher solar intensity. So warmer, right yeah, I'll just you know, quickly summarize this like nice quote from Dr. Hanley. So he basically explains, eggs in colder places are darker brown, and then as you go to the tropics, and even like temperate zones, there basically are more competing selection pressures. So there's also ends up being more variation as you get into these more temperate climates, which is really interesting. They also noticed that darker colors also appeared in some hot and humid regions, too. So for example, in Indonesia; and they think that this could, again, be strongly correlated with like survival, and, you know, birds having to deal with things like predation and you know, maybe diseases that are particularly strong in those areas. And so it's more advantageous to have darker eggs. But yeah, really interesting. Yeah, yeah.
Shekerah Primus 11:46
This is so cool. I kind of feel like humans, maybe were mimicking birds a bit right, because in colder temperatures you do tend to wear darker clothes at least and then in warmer climates, you tend to you know, dress more brightly; I feel like in the Caribbean or like even Africa, right lots of bright, bright colors. I think we're, we're mimicking birds girl.
Fatu Badiane Markey 12:11
What is it art imitates life? Birds imitate life? I don't even know how to say it properly.
Shekerah Primus 12:18
I don't know, I don't know, we learned, we learned from the birds and we learned from our environment; or you know, this darker clothes are thought to be warmer so maybe dark and color that's what it's about that it helps the developing chicks stay
warmer.
It's very, very interesting. I love that so um, so how are birds able to make all of these different colors in their eggs like I've seen blues like speckled eggs, green, white, you know whites pretty common; so white and brown eggs I feel like it's what we have, I've seen commonly just buying eggs at the supermarket but it also seems like really like blue speckled eggs that are like fancy, like different types of different types of eggs that I don't buy when I look at them, I say, Oh, you're so pretty
How are birds able to make these different colors in their eggs?
Fatu Badiane Markey 13:15
Yeah, so the answer is way simpler than I thought it would be. So there are only two pigments blue and brown that exist in birds. And that creates all of these colors that we see. And basically the different concentrations are what allow for all of these different colors. So when you have the combination of these two pigments, plus the white calcium carbonate of the shell, you get all the colors of the rainbow basically. I think of like you know when you're in kindergarten and you're first learning how to like mix, like primary colors, you know, and then you're able to make like the whole spectrum. That's totally what it makes you think of but yeah, blue and brown. And then you can get like blue, green, white is like no color brown, speckles like everything.
Shekerah Primus 14:02
Mm hmm. Very cool. So seems like a very sort of straightforward biological solution to get these different colors going. But we're still sort of trying to figure out all the the whys and be sure about the whys, but the how is pretty straightforward. That's cool. Yeah, so So what about chicken eggs? As I said, I've seen white and brown chicken eggs. Are those also related to things like climate or environments?
Fatu Badiane Markey 14:37
So
with chickens, not exactly. So with this case, the color of the chicken egg is mainly determined by the hens genetics. That means the breed of the hen is going to dictate the color of the egg that will be produced. So for
example, Leghorn
chickens lay white eggs, Orpingtons, lay brown eggs, and then Americana, lay blue eggs. And then you also have olive eggers and that's a breed that lays olive green eggs. So in this case, you know, just like I said before, the different eggshell colors come from pigments that are deposited onto the shell. And if we're going to get really technical, all of this is, is happening as the egg forms in the hens oviduct, right, and the oviduct is sort of like this tube like organ. And that's basically how the egg travels along from the ovary and like, you know, goes down the track to where it ends up in the nest. Because it's just gonna be like a very, very simplified version of that.
It's like the birth canal is it?
It is basically, yeah. But So this involves a five stage process. And during the fourth stage, so almost the last stage of the process, so very late on is when there's a gland called the shell gland, deposits the pigments onto the, onto the shell and that produces the color. So in short, different breeds of chicken deposit different pigments on the shell as it forms and that changes the exterior color of the shell.
Shekerah Primus 16:15
Cool.
So tell me about these olive eggers. I don't, I don't believe I've ever seen olive green eggs that I remember anyway, have you? Where can they be found?
Fatu Badiane Markey 16:28
I have not, I have not, right. Yeah, so I guess this is like a special breed of chicken. Yeah.
Shekerah Primus 16:38
Okay, so what are the different pigments?
Fatu Badiane Markey 16:40
Yeah, so
the different pigments, so the brown pigment is called protoporphyrin. And then when that's deposited on the shell, you know, like I said, it's really interesting though, because all of this happens really late in the process. You will notice with chicken eggs, even though the outside of the shells a different color, usually that color doesn't transmit to the inside. Right, so that's also part of the reason why the yolk and the white of an egg is always yolk it's yellow, and the white is like clear until you cook it. But also if you look at the actual inside of the shell, it still is white. Now for blue eggs its a little bit different story so that pigment is called oocyanin, and this pigment is able to penetrate both the exterior and interior of the shell. And will make both of those blue.
Shekerah Primus 17:33
Interesting.
Fatu Badiane Markey 17:33
So now the story, yeah, it gets even more interesting though, because since the genetics of the hen that determine the color of the egg. That also means we can crossbreed chickens to get different varieties of egg colors and I'm sure that's probably how these olive egger breeds you know come about. There's also another breed called easter egger and they lay really really interesting eggs. So each hen in this case lays a different color day and that means that aids can be blue, they can be green, they can be pink, or they can be blue, green mix, and even more interesting. So hens will only lay one color of egg their whole lives and this will not change. So once they start laying blue eggs, they stick with blue
all the way through.
So Shekerah wasn't that egg-citing?
Shekerah Primus 18:38
Yes, Fatu it was egg-citing.
Oh my goodness. Yeah. Thank you so much for teaching us all about egg colors. It was, it was really cool. I didn't know. Well, any of this; is really cool to learn all about how bird eggs get their color. And also what are the reasons for the different colors. I think that is really interesting. You know, scientists trying to figure out well why are they all these different colors? So yeah, thanks so much for sharing that with us. Yeah,
Fatu Badiane Markey 19:16
I was also just like really fascinated by this. Like once I read one article, I have to pull up like 50 more and be like, What is going on? Because it seems like such a simple thing. Right? But then like once you get into like it's really complex, because like you're forming the egg and then the pigments have to get deposited. And then it's also reading this really interesting thing that I didn't go into depth here, but even for like how eggs get their speckling. We're not 100% sure about that. But the idea is that the speckling basically means that you're adding more pigmentation in one part of the egg than another. And there's a theory that that additional pigmentation is basically to help the egg structurally. If it's like in certain areas, so it's like adding plaster you know, or adding cement to the spot you know, that needs a little bit more support. And even that is so fascinating because it's like as the egg is forming, how does the hens body like know like, oh, this part of the egg, you know, is a little weak. Let me put a little bit more pigment here. So it's just a whole, literally a whole new world. So interesting.
Shekerah Primus 20:32
I bet I know the answer to that, I bet it's something like a signal cascade. There's always a signal cascade.
Fatu Badiane Markey 20:43
Okay, I bet there's a kinase in there somewhere.
Shekerah Primus 20:45
You know there's a kinase in there.
Fatu Badiane Markey 20:50
And so, you know, like, when I think about chickens, you know, so okay, so part of the story is also really interesting because we have like birds in the wild. But then we also have chickens, which are domesticated and my guess is with chickens, because they're domesticated and have been with humans like forever, at a certain point, you know, we selected certain breeds, maybe for certain colors, you know, in particular regions, based on how common they were. So like, when I think about the US, you know, we have both white and brown eggs, that maybe because the US is pretty temperate, it's possible that you know, and it does get cold. Maybe at some point brown eggs were like the norm and then chickens that produced white eggs were introduced and that's, you now have both. But like, when I go overseas, yeah, right. And when I go overseas to where I am now, like in Kenya, I really only find brown eggs. I don't find white eggs so you know, definitely with chickens. It's like humans played a major role in like, you know, whatever, I guess like a color is also like, the preference of society or culture or like whatever. So yeah, so little bit of egg-stra knowledge for all of us. Last one I promise.
Shekerah Primus 22:17
So cool. So what about, so you were saying that because chickens are domesticated that they could have been chosen for their egg color or maybe for some other traits that were beneficial for domestication? Right. So what about chickens in the wild or like wild turkeys or something like that? What color eggs do you see there?
Fatu Badiane Markey 22:40
That's a good question. And I think we'll have to save that for part two; we can do like chicken evolution or something, you know. So interesting. But yeah, that's a really good question Shekerah; because there are wild versions of chickens out there. So it's like what's going on with them? Yeah, maybe they don't have white or brown eggs like maybe because they've been left to their own devices. Their eggs are totally different. Yeah. Yeah.
Shekerah Primus 23:10
Are turkeys in that same boat as chickens? Is that considered? Their egg color when we study them.
Fatu Badiane Markey 23:16
I so, I didn't. I specifically
looked up chickens when I was doing ,y research. Yeah, I didn't look up other domesticated birds, but again. That's why we can have a part two.
Shekerah Primus 23:28
All right, Fatu just leave us on a cliffhanger. But thank you, thank you so much from me and from our listeners for doing all this research and teaching us all about how birds make, I can't even say it, how birds make their eggs colorful. Or, how bird eggs get their color. Oh no. You said telling us more about color story of bird eggs get their colors. So that's it for our show today, listeners. And with that, we'd like to thank you all for supporting our podcast. If you'd like to reach out to us, please send us an email at love science podcast@gmail.com And until next time, bye everybody.
Transcribed by https://otter.ai