miraculous bird nests (vs. wily nest predators), with brett degregorio

miraculous bird nests (vs. wily nest predators), with brett degregorio

His lab there studies wildlife behavior, interspecies interactions, and conservation biology. His special interest? Reptile and avian conservation and behavior. (That’s Brett, below, holding a model “snake” used in field research.)

We talked about all the things birds incorporate into their nests—as status symbols, or as protection against predators, which is how most eggs or baby birds are lost—and how a species’ nest style is so true to form, Brett says, that, “You don’t even have to see the bird that built the nest to know what species it belongs to.” Amazing.

Read along as you listen to the April 27, 2020 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here). (Above, great crested flycatcher photo above from Wikimedia, by Andy Reago & Chrissy McClarren.)


Margaret Roach: Hi, Brett.

Brett: Hi, Margaret. Thank you very much for having me today.

Margaret: I’m one of your fan girls, you know; I’ve told you that before [laughter]. I’m one of the crazy people who reads every research report that you publish.

Brett: That’s amazing. You’re my only fan.

Margaret: It’s wacky. So just for background, I thought, tell us briefly kind of about the work you do and what your lab does. I mean, on the homepage of your lab, there’s turtles and lizards and snakes and all kinds of things.

Brett: I’ve always been a little bit all over the place [laughter], but my two loves have always been watching birds, and finding and studying snakes. And my PhD research and some of my current research finally gave me the opportunity to put those two things together. And so I now spend a lot of time working myself and with my students to figure out how snakes find bird nests and what birds can do to prevent that from happening.

great crested flycatcher [photo, top of page]. And then one time, I turned my head just at the right time, and it was picking up a shed snakeskin out of the wall. There’s a lot of garter snakes in the stone wall. They love it in there, and they wriggle out of their old skin and leave it behind. And this flycatcher apparently knew that he or she or whatever could find, I don’t know if it’s a he or she, could find snakeskins there and wanted to collect them. And I read that they use them in their nests.

So, tell us about that crazy thing. I mean, how in the world, Brett [laughter], does that bird know to do that? And why? Why does a bird do that? And do other birds do that? I mean…

from Wikimedia by MimiMiaPhotography.]

Margaret: Wow. And I mean, my head just goes to the like, “Who told the bird this was a good idea? What bird in its ancestral line how many billion, thousands of years ago figured this out?” I mean, it’s amazing. So, it’s an anti-predation strategy that this animal has developed. And in those tests that you said in 2006, they sort of proved it? They examined enough nests to prove that it did have a positive effect?

Brett: They did. What they looked at were a bunch of artificial cavities, basically bluebird boxes, but for flycatchers. And they put a third of those nest boxes, they put nests with snakeskin inside the box; and a third of them, they hung the snakeskin right outside the box; and a third of them were just regular nests without snakeskins. And what they found is that the flying squirrels stayed right away from those nests that either displayed or incorporated those snakeskins.

Margaret: It’s amazing. Now, so, you’re into snakes. You’re into birds. This is about a relationship among snakes and birds, actually in a couple of ways. Well, the snake sometimes go up the tree, looking… They go up the tree looking for the flying squirrel, is that what goes on? Or sometimes to get into the nest cavity?

Brett: I believe that snakes, particularly those ratsnakes, they love to climb trees, and they’re always looking for a good place to hide out. And one of their favorite places to hide is in those hollows of dead trees, those tree cavities.

Margaret: I see. So, snakes and birds, and they have a common ancestry, don’t they even? I mean, I’m not so good with paleontology and sort of the phylogenetic system of grouping things according to their ancestry or whatever. Are birds and snakes related sort of? [Laughter.]

Brett: Yeah. Certainly not my strong point either. But yeah, they definitely come from a shared ancestor.

Margaret: Do other birds do this—are there other birds who go looking? And is it known whether it was the male or the female who does this? I don’t know who builds the nest in the great crested flycatcher, for instance. And I don’t know how to tell them apart necessarily. Are there other birds that do this, collect snakeskins and use them in this way?

blue grosbeaks do it really frequently. Robins occasionally do that. [Above, blue grosbeak photo from Wikimedia by Andy Reago & Chrissy McClarren.]

Actually I spent the day today watching some robins build a nest right outside my front door, and they’re incorporating a long piece of tape off of a cardboard box, so it looks just like a snakeskin. And I’m guessing that they’re tricked by it.

We’ve seen European birds do this as well. And there seems to be a theory that these birds, who don’t nest in cavities, but instead build big platform nests so a little cup nest, they do it as kind of a status symbol.

So, there’s one bird that’s a small hawk, called the black kite, and the more snakeskins and white pieces of plastic they incorporate into the nest, the tougher they’re telling their neighbors they are. And the birds that incorporate lots of these white pieces of plastic and snakeskins, they tend to be really dominant, and other birds will not mess with them. And the kind of subdominant or weaker birds, they’re too afraid to incorporate these ornaments into their nest because they know they can’t win those fights. So, they have really plain nests.

Margaret: [Laughter.] That’s just crazy. It’s fantastic. There’s a, forgive me for saying this, pecking order among birds.

Brett: [Laughter.] That’s great, that’s perfect, yeah.

Margaret: Oh, my goodness.

Brett: And there’s even another European bird called a great reed warbler, who’s a lot like our red-winged blackbirds. And they’ve got a very similar breeding style, where there’s one male who defends a big territory, and he has multiple females nesting within that territory. And the females are always looking for snakeskins. And the more that they can incorporate into their nest, the more dominant they are within that kind of female matriarchy, and the more attention they get from the male who owns that territory. So, it’s, again, kind of a status symbol among these reed warblers.

Margaret: Oh, it’s a currency. You said “pay attention”—you’ve been paying attention to birds nests. And last year, I almost walked right into it in the shrubbery here. I was doing some raking or whatever in the spring, and I came upon, at maybe head height in the fork of a branch of a large shrub, this cup nest. I took a picture of it [below] and I went inside and I looked up, tried to look up, the materials I could recognize: It was lined with pine needles and it had bits of birch bark and also some paper from a paper wasp’s nest, and otherwise was kind of like a woven small cup nest. And sure enough, it was the exact signature, the exact description of, “How to build a nest if you are a red-eyed vireo.”

Brett: [Laughter.]

the DeGregorio Lab website.]

Margaret: I see, O.K. Well, Brett DeGregorio, I’m glad to finally meet a little more, rather than just reading everything you publish. And I hope we’ll talk again soon. Thank you so much for sharing some of your expertise with us today.

Brett: Oh, thank you so much. It was really a pleasure to speak with you. I appreciate the opportunity.

Margaret: We’ll talk soon again.

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