The Science of Birds - Random Bird Thursday: A Tiny Island Dweller That Likes Vines

Episode Date: July 2, 2026

In each Random Bird Thursday (RBT) episode, the goal is to highlight a bird species that probably isn't going to get featured in a full-length podcast episode. These are birds we might overlook, even though they certainly deserve some appreciation and attention. ~~~~~~~~~~~~~~~~~⚠️ SPOILER ALERT!The featured species in this episode is the Rufous-sided Gerygone (Gerygone dorsalis).Sound Citations:Colin Trainor, XC138529. Accessible at www.xeno-canto.org/138529.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. And in case you hadn't noticed, it's Random Bird Thursday. With over 11,000 bird species in the world, random Bird Thursday episodes give us a chance to celebrate some of them that we might otherwise overlook. We still don't know what species we're doing, so let's go ahead and push the random bird selector button to see which species we're talking about today. Okay, interesting. We have a little brown bird, the Rufus-sided Gerigone, Gerigone Dorsalis.

This is a bird from the islands of Indonesia, and there's a good chance that nobody listening right now has ever seen this bird, but that's why it's fun to talk about. We're vicariously exploring the world of birds together. And let's get started. So this is a small bird, the Rufus-sided Gerigone. It's vaguely warbler-like, even though it's not a warbler. But if you can picture a warbler, that kind of body shape, bill shape, it's got a pretty big head for its body, I would say. And as I said small, this bird is only about four inches from beak to tail,

which is about 10 centimeters. The bill is blackish gray, and the eye color varies from quite red, a reddish brown, to dark gray or yellow gray. When I was exploring pictures of this species on the internet, some of them looked almost like different species because of the different eye colors.

Now, in terms of plumage, the upper parts are generally a grayish brown or olive brown, although there is that kind of rufousy color, more so on some subspecies than others. And in the underparts, they're white below, but there is a pale rufus or ochre kind of wash on the sides of the breast and flanks. But overall, kind of a little brown bird, somewhat drab.

And both males and females look identical. There's no sexual dichromatism or dimorphism. So what do these little guys sound like? What does the rufus-sided churigone sound like? Well, there are a couple songs that have been described. Song 1 is described as a sibilant, sort of even-pitched trill almost, with it's kind of monotonous, all on the same pitch. But then song 2 is more complex, and it's a bit slow,

and it includes some slightly warbled notes. So that again adds to this idea of it being warbler-like. So I've got a recording for you, and I think this is song two. No, no, not song two by the band Blur from the 90s. No, the song two from the Rufus-sided Gerigone. Now, in this recording, there are some loud cicadas buzzing, loud insects. So you'll have to listen for the bird's warbly little song

behind all that racket being made by the insects. Okay, here we go. As for behavior, this is an active species. It frequently flicks its tail and wags its tail slowly up and down. And apparently, it's got a pretty nice demeanor, at least in some places where it lives. It's considered a confiding species as it's foraging around in the shrubs, letting people get fairly close. So let's talk about the name. Rufus cited Gerrigany.

So Gerrigany is the genus, and there are a number of those species. And apparently, if you break down the etymology of the word gerigone, it translates. it translates roughly as being born of sound or born of voice. Then it has to do with these little guys singing in the bushes and the naturalists who first assigned this genus to these birds. So that's gyrigone. And then the second part of the scientific name is dorsalis. And that means of the back, right?

Like dorsal fin on a fish or a shark or a dolphin or an ichthyosaur. And I guess that refers to the darker color on the back. for this particular species. So Gerigone d'Orselis. Now the family is Acanthysity. This is the family of thornbills in their allies. They live mostly in the Australasia region, and for many people in Australia,

these are the little brown birds of their world. Acanthysity has 66 species, and then the genus Jerigone has 20 species. Now, normally I like to tell you, about the closest relatives of the species that we're talking about. There was a paper that was published in 2012 called The Evolution in Australasian Mangrove Forests, multi-locust phylogenetic analysis of the Giorigonee warblers.

See, they even call them warblers. But they're not closely related to North American warblers or warblers in Eurasia. So that paper was a phylogenetic analysis, meaning it created or the result was an evolutionary tree, showing relationships among species, but wah-wa, Gerigone, Dorsalis was not one of the species that was sampled and included in that paper. Oh, well, so we don't really know the closest relatives of this species. But what we do know is that there are five subspecies that are recognized,

and these are distributed across different islands in Indonesia. And that makes sense that there would be different subspecies because this bird has a range that is in the eastern Lesser Sunda Islands and the Kai Islands, all in Indonesia. So if you're trying to picture where these islands are, they're north of Australia's northern territory, right? So north of Darwin and all that. And west of the island of New Guinea.

The lesser Sundas and the Kai Islands, these are like archipelagos within the Indonesian archipelago or melee archipelago. Archipelagos within archipelagos, like a, like some sort of fractal or something. I just like the word archipelago. It's one of my favorites. So any chance to say that many times, I love it. Now, this region that these birds live in is a fascinating region.

In fact, I did an entire podcast episode on it. That was episode 46 about Wallace's line. Because this region is called Wallasia, and that's because of the biogeographic history of Alfred Russell Wallace being there. So check out that episode if you're at all curious. But the Rufus-sided Gyrgyzni, its preferred habitat on those islands is lowland and coastal forest. It likes to hang out on forest edges, as well as in secondary forest, mangroves, and even some lightly wooded cultivated areas.

It seems to be particularly fond of vine tangles in dense forest. This bird is non-migratory, so it's resident on those islands. and in terms of conservation, good news. This species is classified as least concern. That's always good. And in fact, I could not find any references to known threats to this species. Habitat destruction is pretty common around the world, so it's hard to believe that that's not happening on those islands,

but we'll take a win when we can get it, right? A species that is maybe doing okay. Now, these little birds are insectivorous, which you shouldn't be surprised, given it their warbler-like overall shape and behavior. And so they glean for insects from under leaves, often in the middle story of the forest. So 10 to 20 feet off the ground, and again, they like to hang out in vine tangles and go foraging there. But they'll also forage in low shrubs or in the grass. And they tend to hang out in pairs, pairs of rufous-sided gyrgygonies, but they'll also join

mixed species flocks. And one of the species they tend to hang out with is the yellow-bellied white eye. Now, I'd like to tell you about how these birds breed, but there is essentially no information other than the fact that maybe, just maybe, this species is affected by a brood parasite called the Little Bronze Cuckoo. So those cuckus might parasitize the ruficited gyrigone. Now, have I seen this species? No, I have not. I have not spent any time in that part of the world. I've been in the northern territory in Australia, and that's about as close as I've gotten. I'd love to spend some time in Wallasia, in that part of Indonesia someday, and I'd love to see the diversity of birds that are there. I think it'd be a really amazing place to experience, but I have not. So maybe someday.

How about you? Have you seen the Rufus-sided Triggini, Trigone, Dorsalis? Tell me your story. Let me know. My email address is Ivan at Scienceofbirds.com. And that is all for Random Bird Thursday today. Thanks for listening. Thanks for your interest in birds. And I'll talk to you next time. Peace.