The Science of Birds - Random Bird Thursday: A Species with an Executioner’s Axe for a Face

Episode Date: November 28, 2025

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 White-thighed Hornbill (Bycanistes albotibialis)White-thighed Hornbill sounds (Xeno Canto recording XC617118)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 I think you know that it is random bird third. Thursday. Random Bird Thursday episodes are relatively short and sweet. In each of these RBT episodes, I spotlight a bird species that probably won't get

featured in a full-length normal episode. There are over 11,000 bird species in the world, so Random Bird Thursday gives us a chance to celebrate one of them that we might otherwise overlook. So who do we have today? Let's push the random bird selector button and see who we're talking about. All right, excellent. We have the white-thied hornbill, by Canistis Albo-Tibialis. Hornbills are always super cool, so this will be fun to talk about this species.

Okay, so if nobody has any objections, I'm just going to go ahead and get right into it. What does the white-thied hornbill look like? Well, can you picture a hornbill? In general, they have pretty large heads and really large thick bills that are generally down-curved, and many of them have longish tails. Well, the white-thied hornbill definitely has a massive head and bill relative to the body. The bill is down-curved, and it has on top of it something we call a cask, C-A-S-Q-U-E. That's the sort of weird thing growing out of the top of the bill. And the shape of it varies

across different hornbill species, and not all hornbills have a really dramatic cask. But this one does. It looks kind of like an upturned axe blade, like something an executioner would use. and that blade comes to a point in the front towards the tip of the bill it's pretty dramatic now that cask is present on the male but not so much on the female she has a much smaller bill

the bill color is dark brown with a creamy undertone and it's lighter colored towards the tip and the base and the cask tends to be more of that cream color as well the overall body size is somewhere between 24 and 28 inches long from beak to tail So when you see this bird from a distance, it's going to give you the impression of an overall very black and white bird, very boldly patterned, big blocks of black and white. The head and body are mostly black, the outer part of the wing and the lower part of the body, and the tail tip are white.

And of course, it has all white upper thighs. So it looks like it's got some nice pantaloons or some nice breeches, puffy white pants like they used to wear in like the Renaissance or something. that's what I'm picturing. And I mentioned the head is black, and I should point out that this species has cold black cheeks in terms of the feather color. And that's important because that is what differentiates this species from another closely related hornbill

by Canistes cylindricus, the brown-cheeked hornbill. And that one, of course, has brown cheeks. The white-thied hornbill is generally found in pairs or small groups up to maybe six individuals. And this is in Africa, and we're going to talk about that in just a moment. But first, let's listen to what this bird sounds like. This recording was made in the Central African Republic. So you can tell that the calls there are not very musical, kind of guttural and harsh,

and that's typical for many hornbills. All right, moving on from what the bird looks and sounds like, let's talk about the name a little bit, the scientific name. Bichanistis Albo-Tibialis. Now, that second part, the specific epithet, I bet you could almost figure it out. Albo-tibialis. Think tibia bone, right? tibia bone in your leg, and albo comes from like albino, right, from white. So white

thide. Now bichanestes, the genus, that one actually comes from ancient Greek, and the original word meant something like war horn, a horn used in war, and then that became another Greek word meaning trumpeter. So bichanestes related to trumpeting, you know, the sounds and maybe the cask being kind of like a trumpet. So there you go. Bichanistis, and this of course is in the Hornbill family, Bucerotiddi. We talked all about that family in episode 68 of the podcast. And I have to admit this is one of my favorite bird families of all time. I love hornbills.

That's one reason that I chose a hornbill as the logo for my birding tour company Wild Latitudes. Now within the family Busserodidae, the white-thied hornbill is one of six species in the genus Bichanestes. Its closest relative is the bird I mentioned earlier, the brown-cheeked hornbill Bichanestes cylindricus. It has a cask that's a bit more cylinder-shaped, so thus the name cylindricus. Oh, and the white-thied hornbill used to be considered the same, the same bird as the brown-cheeked hornbill. They were all just considered one species, and then the white-thied hornbill was split apart once it was recognized that it was unique. Okay, so these guys are in Africa, and I would say, you know, it's sub-Zaharan Africa, but more central west.

So the westernmost populations of the white-thied hornbill are in southwestern Nigeria, and the range extends all the way over to western Uganda and covers a large part of the Congo, the Democratic Republic of the Congo, and northern Angola, and it includes a number of other African countries in that part of the continent. Its habitat is evergreen and and semi-evergreen rainforest. That whole region there is pretty much equatorial, right? So we're talking hot and humid, lots of rainforest. The white-thied hornbill is found up to an elevation of about 3,600 feet or 1,100 meters.

And that's in the mountains that straddle the border between the Democratic Republic of Congo and Uganda. Across its range, the white-thied hornbill is in many places sedentary, meaning it just kind of hangs out in the same part of its range all year long but in other populations other places these birds can be nomadic they sometimes make large movements to track the resources that they eat and we'll get to that in just a moment but basically we're talking about fruit spoiler alert research has shown that this species selects what it eats based upon the nutritional concentration and the mineral concentration in the food

they change their diet to meet their nutritional needs throughout the breeding season. And that's not necessarily unique to this bird. Many birds do that. But there is some research explicitly showing that for the white-thied hornbill. So in terms of conservation, this bird is actually doing pretty well. The IUCN has its status as least concern. And that's great. However, that doesn't mean this bird is free and clear, forever and ever, and it's never going to have a problem.

because there's a couple things going on that are, in fact, threatening. And those two things are habitat loss and local hunting. And conservation groups think that this species might already be in decline, even though it's okay right now. So in terms of habitat destruction, this bird is generally in low densities. It's a long-lived bird. It doesn't live in high densities, you know, large populations.

And it has a pretty broad range, so it needs large tracks of forest. For example, in southwestern Nigeria, research has shown that this species is strongly associated with the larger forest fragments. So there's some habitat loss, and on top of that, there's local hunting pressure. In one case, in Cameroon, of all the bird species being eaten as bushmeat, this was the species that was most frequently consumed. And one last thing to say about conservation, researchers have figured out that, unlike maybe some hornbills, this species doesn't seem to be limited by the availability of nesting sites,

of cavities, and we'll talk about that in a sec. Instead, it seems to be limited by food availability. So as conservationists work to protect this species in the future, that would be something they'd have to consider, right? Maybe rather than focusing so much on nesting sites, they could focus more on food, assuming that that research holds up and that that's the real situation. Okay, so yes, I said that these guys eat fruit, and that's not too surprising. If you know anything about Hornbills, they are specialized for eating fruit. So the primary diet of this guy is fruit, fruit, and more fruit with a side of fruit and fruit for dessert. Approximately 90% of the diet is some kind of fruit, or even more in some studies.

And it's not like they're picky. They don't just eat fruit from one or two different plants. In fact, they've been recorded as eating fruit from at least, 55 different plant species. So a hornbill lands on a branch or in a tree that's fruiting and it starts horking down those fruits, maybe two to three per minute and the bird might just kind of hang out in one small area for up to an hour or an hour and a half,

just lazily stuffing its gullet with fruit. Sounds like a pretty good life. Now, they do sometimes eat other things. For example, they'll eat invertebrates like insects and spiders as a supplemental source of protein. So for insects, we're talking about damsel flies, dragonflies, mantis, ants, grasshoppers, wasps, and they occasionally will eat bird eggs of other species

and even nestlings in chicks, which is kind of heartbreaking, I know, but that's just how it goes. And remember I mentioned that there was that study that tells us they select what they eat based upon nutrients and mineral content. so in the early breeding season these birds are going to eat a diet significantly rich in calcium that's what this research discovered and as the breeding season progresses through the brooding and fledging periods white-thied hornbills will switch to a diet that is rich in iron and that has more calories from fat when they're foraging for fruit or whatever most of that is occurring way up in

the canopy of large emergent trees or isolated trees we're talking 80 feet or 150 feet off the ground or 25 to 50 meters. What do we know about how these birds breed? Well, there's not much known about how the white-thied hornbill breeds. We can assume that it is monogamous, since that's the standard situation for hornbills. And we know that it's a cavity nester, which is also standard. And you may remember the remarkable thing about most hornbills is that the female is the one that's going to be in the nest cavity. and the mail seals are up in there using mud.

So they find a natural cavity, and the male brings beakfuls of mud and plasters a wall essentially around the entrance sealing her in. And she'll kind of finish off the job by using mashed up fruit and even some of her own poop as a sort of paste to seal up the hole even further so that she cannot get out while she's taking care of the chicks. She's sealed in.

She's entirely dependent on the male to bring her food throughout the time that she's in there, which is really amazing. So the nest is made in a natural tree cavity. These birds are not excavating their own cavities the way a woodpecker might. A white-thied hornbill's nest is typically situated about 65 to 80 feet off the ground, which is 20 to 25 meters. And this is often in a live tree, usually on the main trunk of the tree, or maybe on a really large branch.

So the female's in there She's sealed in The male is coming back and forth to the nest He feeds her by regurgitation And he's going to deliver Maybe 12 fruits every time he comes back And he's going to do that 14 to 18 times per day

Now again there's not a lot of data Supporting this this is maybe based on just One or a few observations of nests And yeah we don't know a whole lot about the eggs But we do know that Typically there are two nestlings in there. And unfortunately, it's usually only one of them that emerges, that fledges. So only one is really going to survive to continue on the family. It's rare for there to be two surviving

fledglings. And once they bust out of there, when it's mom and the surviving fledgling, or maybe occasionally two, they come out. They're going to hang out as a family for a little while, but then the youngsters are off on their own. We don't know the lifespan of this species. But hornbills are generally long-lived birds. So maybe we're talking 10 years or more in the wild but that's just speculation for this species.

So the white-thied hornbill by Canis D's Albo Tibialis. I have not seen this bird yet. It's in a part of Africa. Well, I was in Uganda. So I guess theoretically I could have seen this bird in the western most Uganda but I

haven't recorded it and I don't recall so maybe someday. and I'm curious if you've seen one. And I think with these random bird Thursdays, it'd be kind of fun to ask you guys if you have an experience with the bird we're talking about and you can send me an email and let me know how that went. Hopefully it went well.

All right, that is it for Random Bird Thursday this week. Thank you so much for being here. I hope you enjoyed it. Hope you learned a few things. And I hope you're looking forward to the next one. Cheers.