This is an I-Hard podcast.

Guaranteed human.

Approximately 1% of all bird species are total jerks.

No, approximately 1% of all bird species are not seagulls.

They're what are called interspecific brood parasites.

And fine, they're not really jerks, but evolution has endowed them with a profoundly jerk-like strategy.

You see, interspecific brood parasites put their eggs into the nests of other species, often without

them knowing it. And to add insult to injury, the parasitic birds often damage the host nest

as well. For example, just in case the parents of the parasitized nest can count, the brood parasite

takes one of the host eggs out of the nest and yeats it overboard.

Now the nest has the same number of eggs as it did before the doting parents went out to grab a quick snack,

but one of those eggs is not their own.

And then the brood parasite mom typically scrams, leaving the host parents to do the difficult job of raising the kids.

How did this deadbeat parenting strategy evolve?

And why can't the host species seem to figure out what's happening and fight back?

On today's episode, we're going to dig into interspecific brood parasitism.

And I'm going to be absolutely thrilled to be combining some of my favorite topics, animal behavior and parasitism.

Welcome to Daniel and Kelly's parasitic universe.

Music Hi, I'm Daniel. I'm a particle physicist, and I have zero tolerance for parasites.

Hello, I'm Kelly Weiner-Smith. I study parasites and space, and I have all the time in the world for parasites. All right, Kelly, well then, my question for you today is, how many non-human species are there in your brood? Oh, you're asking me about pets. You've already asked me about pets. You just found a different way to ask. I guess, you know, you need an update, right?

Because you asked me this a couple weeks ago, and the number changes regularly. But now I'm

framing them as parasites on Kelly's Goodwill. Oh, probably just my dog biscuit, because she's been,

...