The Science of Birds - Random Bird Thursday: A Master of the Sky That Flies Fast and Far

Episode Date: September 11, 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-throated Needletail (Hirundapus caudacutus).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'm happy to say that it is random bird. Thursday. In this relatively short, mostly unscripted episode, I'll be spotlighting a bird species that probably won't get featured in a full-length episode.

Because there are over 11,000 bird species in the world, random bird Thursday is our chance to celebrate a species we might otherwise overlook. So without further ado, let me push the random bird selection. button here and let's see who we're talking about today. Okay, we've got a good one here. We've got white-throated needle tail. Herendapis, Codacutus. So this is a type of swift. It's a rather large swift and it's found primarily in Asia but also in Australia. And we'll get to all. all of that, of course. Now, as you may or may not know, I've spent quite a bit of time in Asia

in the last year or so. I had two big trips, each of them about two and a half months long each. And so I've been in places where the white-throated needle-tail is found. And how many white-throated needle-tails have I seen? Zero. Now, the thing is, they were probably zipping around through the sky right over my head, but I just didn't see them. And to be fair, I wasn't probably looking super hard for them. So yeah, it was an oversight. I'm kind of kicking myself for it now. This is a great bird. So with any luck the next time I head over there to Mongolia or Japan or China or Nepal, all these places I could have seen them, Bhutan, hopefully next time. Right, so time's a waste and let's get on with talking about the biology of this bird, the white-throated needle tail.

What does it look like? Well, for a swift, this is a large one. It's got a long body that's kind of thick and full for a swift. It looks like a big chunky cigar, very tapered on the front and back end, because, of course, it's aerodynamic. The wings are long and broad, and they come to sharp points. They look sort of sickle-shaped or saber-shaped. shaped, very sleek. The bill on this swift is typical for swifts. It looks really small,

just like a little nubbin at the front end of the bird's face, but the bird can open its mouth quite wide, so the actual gape, the size of the opening of the mouth, is rather large, so the beak is not, it's kind of a deceptive thing. It looks smaller than it is. In terms of plumage coloration, the wings are overall pretty dark, but on the upper side, there's a really nice bluish sheen, bluish green sheen, kind of almost metallic. And the back of the bird, the mantle between the wings, is this white, it's, I was going to say, it's this white color. It is white, but kind of a dirty off white that blends into the gray and the darker feathers of the back. The body in general is pretty dark. The belly is brown,

but there are some nice white accents. So this is, of course, the white throated, tail. So yes, it has a nice white throat patch, but it also has white in front of the eyes or on the forehead. So the lores in front of the eyes and the forehead are white. And then at the back end, there's what they call this kind of horseshoe shape. So the undertale coverts are white. And then coming up on the flanks on the side, there are these two sort of horns or extensions of that undertale area that come forward to basically the armpit area almost. So if you look at it from directly underneath, it creates sort of a horseshoe shape. Now I should point out that there is some variation in this species. There is another

subspecies that does not have that white forehead and white lores. So it just has dark feathers that come all the way down to the upper beak. Still has the white throat, but not the white forehead. We'll talk about the subspecies in a moment. Both males and females are similar in this species. So there is no sexual dichromatism. And I would say for the sounds, for the voice of this bird, pretty typical for swifts. The white-throated needletail makes rapid sort of insect-like chattering and twittering calls, maybe a little softer than some of the sounds that you might have heard from maybe common swifts. But still, it's not musical. It's high-pitched, kind of a twittering, chattering sound. And apparently when hands,

handled, these birds can give a querulous call. Quariless or plaintiff, like, hey, buddy, can you just, can you put me down? Like, what do you hold me for? This doesn't need to happen. What are you doing here? I'm a swift. I'm supposed to be in the sky. As much as I might want to hold one and pet one, I'm sure that's probably never going to happen. I'm never going to hear that querulous call. Right, so let's talk about the key behavioral traits of the white-throated needle tail. now this is a swift so we know they fly around a lot but this species is one of the ones that spends most of its time in the air most of its life is spent in the sky it flies around very gracefully very powerfully with these kind of slow purposeful turns and arcs and it makes rather shallow wing

beats and yet can fly very very fast now if you look online if you look this bird up the way i did, you might come across some sources that say this is the fastest bird in terms of flapping flight in the world. And those sources might report something like a speed of 105 miles per hour, which is 170 kilometers per hour. And that's super exciting. But when I dug a little deeper, it seems like there's really no hard evidence that that's true at all. I don't know where that originally came from, this idea that these things fly 105 miles per hour, but it apparently is not true. Now, its cousin, the common swift, Apis Apis, is the record-holding bird for the fastest bird in flapping flight, reaching a speed of about 70 miles per hour or 112 kilometers per hour

approximately. Now, there's no doubt that the white-throated needletail is a fast-flying bird. It's probably one of the fastest flying birds in terms of flapping flight, but maybe not the fastest. Just for reference, you know, we talked about the Peregrine Falcon in a previous episode. The maximum speed ever recorded, least to my knowledge, for that species, is 242 miles per hour, or 389 kilometers per hour. But that was during a dive or a stoop, so not flapping flight. The bird was just rocketing downwards with its wings tucked in. That's how Peregrine Falcons achieve those super, super high speeds.

So anyway, the white-throated needle tail is this graceful, powerful flyer. They make these big circular flights up high, and they're described as being not quite as bat-like as some other swifts. You know, as many swifts flap around really fast and they're kind of erratic and they look almost like bats at first glance. Not so much with the white-throated needle tail. This bird has a little more purposeful look to its flight. And depending on the season and where you are, you might see, not just one of these birds, but many of them, because another aspect of its biology is that it is a social bird, gregarious. These birds will form large flocks, and sometimes in the

thousands, especially on their wintering grounds. And it will also associate with other Swift species in the same genus, so Herendapus, or even the Pacific Swift, which is in another genus. But during the breeding season, these birds are less likely to be as gregarious. They tend to kind of do their own thing, or at least not to associate with other species. That's more of a non-breeding season or migration behavior. Okay, so let's move on now to talk about the family and the distribution, habitat, migration, and conservation. So just a moment to look at the etymology, the origin of the name. As you know, I love to do this kind of thing. So the genus name is

Hirondapus, H-I-R-U-N-D-A-P-U-S. Heron-D-A-P-U-S. And this is a combination of two other genera that have been mashed together. So we have the swallow genus, Hirundo, H-I-R-U-N-D-O, and the Swift genus, Apus, A-P-U-S. That's the genus of the Pacific Swift, Common Swift, other large swifts. So herondapus is like Herundo plus apis. And then we have the specific epithet, the second part, which is cata cutus. And that comes from Latin for words meaning cata, meaning tail and acutus meaning pointed. Because I should actually back up because I forgot to tell you about why it's called a needle tail. Right? So the scientific name reminded me. Cotacutis means pointed tail. So at the tip of the tail, the feathers end in these little spines. So each retrics, right,

each of the retracies, the tail feathers, has a little bare shaft that doesn't have any barbs. And that sticks out only about a quarter inch or six millimeters beyond the squared off rest of the tail. And the tail does look very squared in this bird. So for every feather in the tail, there's this little point sticking out. Now, what is the function of having these little points, these little needles, I do not know. Not sure anybody knows. It may be something to do with species recognition or courtship. But I can tell you that in the genus here in Dapis, all of the species in that genus have that needle-tailed structure. There are four species in that genus, species like the silver-backed needle-tail and purple needle-tail. And the silver-backed is

the closest relative of the bird we're talking about today, the white-throated needle-tail. Those two species are so similar, the silver-backed and white-throated, that back in the day they were considered to be cons-specific members of the same species. So we've been talking about the genus, herendapus, but that genus is in the family, apodidae, the family of Swifts, which includes 109 species globally. There are 19 genera, and one of those, of course, is Herondapus. So where do we find these birds? Well, I mentioned a little bit earlier, that they're in Asia and Australia. So specifically, there are kind of two different populations,

and one of them breeds in southeastern Russia or in Siberia, as well as parts of Mongolia, northeastern China, the Koreas, and Japan. So that's the breeding range. And then the wintering range, non-breeding range, is down in eastern Australia, all the way down to Tasmania and also in parts of New Guinea. And then there's a disjunct population that lives in the Himalayas, in the foothills of the Himalayas, from Pakistan, India, Nepal, Bhutan, and so forth. So overall, this species has an extremely large range.

It covers about 6.4 million square miles, which is roughly 17 million square kilometers. The white-throated needletail is also a rare vagrant in Western Europe, with records as far west, this Norway, Sweden, Great Britain, Denmark, and so on. And in the other direction, it's been recorded as a vagrant in the Aleutian Islands of Alaska, and in the Seychelles Islands, Rodriguez, a bunch of islands in the Pacific Ocean, or Indian Ocean. So across this vast distribution, this range, we can find the white-throated needle tail from elevations of sea level all the way to about 13,000 feet or 4,000 meters. It's breeding, habitat is temperate and boreal forests. So you want to picture these birds breeding either in

northern, eastern Asia, up in the boreal forests there, in Siberia, Mongolia, China, Japan, or in the boreal and temperate forests high in the mountains in the Himalayan foothills. And one of the key features, if not the key feature for the breeding habitat, is the presence of large old trees that have large deep cavities in them, right? Cavities from rot that have been hollowed out or that have been hollowed out by woodpeckers because those are the places that these birds nest. Because the thing is, these birds are aerial, right? They're basically animals of the sky that essentially would never come down to land except for the fact that they have to lay eggs and raise a family. So their habitat primarily is the sky except for that narrow window of time when they need to

breed. And then they need those big large trees with the cavities. So that's habitat during the breeding season. Now in the winter when these birds fly south, they use a wide variety of habitats in coastal and mountainous areas. And they will roost in tree hollows as well. And this is primarily going to be again in Australia. Now, like some of its relatives, the white-throated needle tail seems to possibly exhibit something called nocturnal hypothermia, something we call torpor, T-O-R-P-O-R. This is where the bird lowers its metabolism and its body temperature significantly on a cold night in order to conserve energy.

We talked about this with hummingbirds, right? Hummingbirds do this, and hummingbirds are actually quite closely related to SWIFT. So a white-throated needle-tail in torpor, maybe spending the night in the mountains in Australia, hunkered down in a tree cavity, that bird can lower its body temperature so that it's not burning as many calories to stay warm, and that is a survival adaptation. It's very cool. It's like a little mini hibernation just overnight. Okay, so we've talked about their breeding habitat being up in the north and then going down to Australia, so obviously these birds are migrants, and they are full migrants. they make a long-distance migration between the two areas, and pretty much the entire species does that. But understanding migration in these birds has been challenging for ornithologists because they fly so fast and often at great elevations that they're not easy to observe with a naked eye or with binoculars or whatever,

when they're migrating. For the longest time, it was unclear what kind of route these birds took between their breeding and non-breeding habitats. But fairly recently, there was a study that tracked several of these birds using geolocators. These tiny devices were strapped to the back of these swifts and that would record the timing of sunrise and sunset

and with that information scientists could actually figure out the location the birds were at any given time roughly. But the challenge is you put the little backpack on the bird, you release it and then you have to actually catch that bird again to recover the

data. This is not data that can be collected remotely. So what did they find? Well, the birds were initially captured in Japan, and what they did was they did this kind of figure-eight pattern of migration. They headed out east over the Pacific Ocean for a couple weeks, then they flew directly west over China, unexpectedly, and then they made their way down into Australia, and then kind of reverse that pattern on the way back. So a figure-eight pattern is what they roughly traced. Now, the there were just three birds that were tagged this way, so we don't know that all of them do that, but the two of the birds seemed to be a social pair, maybe a mated pair, and one of the birds

was independent. So all three of them traced that figure eight pattern, so that's suggestive. It's definitely better than what we had before, which was no data. So why would they do that? Why would they take this very nonlinear route? Well, the idea is that because these birds can fly at different elevations, they are utilizing wind patterns. The wind conditions can vary quite a bit at different elevations, basically blowing in different directions possibly. So these birds are trying to minimize the energy that they're expending, and so they want tail winds. They want winds that are pushing them along, helping them fly. so it seems they've adapted to identify the trade winds and other patterns to take the path of least resistance down to Australia and back.

So I guess I didn't explain this clearly. So there are two subspecies. There's the subspecies that breeds in eastern Asia and then ends up in Australia. Then there's that other population in the foothills of the Himalayas. And that is considered another subspecies. So the nominate subspecies, the one that was first named, that's why it's called nominally. that one is Herondapus Cotocutus Cotacutus. Well, the other one, the Himalayan subspecies is Herondapus Cotocotus Nudu-D-I-P-E-S. Now that subspecies, Nudipes, breeds in the Himalayan foothills, but we don't know as much about their migration and where they even end up in their non-breeding season. But it seems like they head down to the Indonesian archipelago, somewhere around there, perhaps.

Okay, so we've got the two subspecies we talked about migration. Let's move on now to talk about conservation. So at the global level, the IUCN, the Red List, has this species in the least concern category. And if you're an animal or a plant or anything, that's the category you want to be in. because it means you're doing okay. So this bird seems to be doing okay, and that is probably because it has that really, really large range. Remember, millions of square miles.

The population seems to be stable, and we're talking about the global level here. But just because you're doing good overall as a species doesn't mean there aren't problems here and there. Because, for example, there have been significant population declines documented in Australia. So there's data that shows that the number of white-throated needle tails wintering Australia, particularly in Victoria, has declined by about 75% over the last 60 years.

75% that's enormous. So in Australia there's a lot of conservation concern for this species, despite its overall global status of least concern. There's a lot of concern in Australia. So what's going on here? Well, one of the things is, you know, that Australian population, they breed up in the Siberian forests, and there's a lot of illegal logging going on up there. So those large old trees that have nice cavities that are perfect nesting areas for these swifts, those trees are being removed, destroyed. In addition to the logging in Siberia, you also have the problem of wildfires, which can be exacerbated by the logging, by all that human activity.

So habitat loss on the breeding territory or the breeding range, that's part of the problem. Other threats could be things that are reducing the food resource. So pesticides, herbicides, things that are influencing the insects that these birds eat, that could be causing a problem. Another challenge for white-throated needle tails is wind turbines. So there are a lot of these in Australia. And because these birds on their wintering range are pretty much constantly in motion, they can fly 550 miles or 900 kilometers a day from one roost site to the next.

And so they're covering so much ground or so much air, I guess they have opportunities to run into these wind turbines and get killed. There's plenty of data that shows that's what's happening in Australia, where dozens of individuals in particular wind farms are found dead, and the data we do have on numbers of SWIFs killed is probably an underestimate. because, for example, there is carcass scavenging. So you get a bird, it gets killed, it's laying on the ground, and then along comes something like a red fox or a feral cat,

and those can remove that carcass, leading to underestimates of how many birds are being killed on wind farms. And to underscore this problem, a really sad thing happened, so remember that I mentioned that these birds are vagrants in Western Europe. Well, back in 2013, there was a white-throated needle tail getting birders really excited in Scotland. People were traveling from all across the countryside to try to see this bird. It was such a rare thing.

Well, unfortunately, that bird ended up on a wind farm and it got killed by a wind turbine as birders were watching. I can't even imagine making a trip to see a bird like that that you're so excited to see and it's a lifer and you just saw it and wow and then bam, and now it's dead. Basically at the hands of humans. So, wow, yeah. Not cool. Now, in terms of natural ways these birds might be killed, they have a couple avian predators,

not too many other predators, but avian predators. Barking owls, nine ox connivans, they're known to attack needle tails, particularly just as the swifts are going into roost, maybe they land on a tree trunk, and then the owls swoop in to grab the swift, or an owl comes in to grab a swift. Paragon Falcons occasionally take these birds, but really the needle. that gets taken by a falcon has to be really off of its game, because white-throated needle tails are generally capable of out-flying falcons just in terms of their maneuverability, so it's a fairly rare thing for that to happen.

White-throated needle tails are flying around through the sky, and what are they doing up there? well primarily they are eating. They've got high metabolisms and they got to fuel that metabolism by eating lots of stuff and that stuff happens to be small flying insects. These are aerial insectivores and that means at least in terms of how they eat, ecologically, behaviorally, that means they're similar to swallows and to things like night jars which we talked about on a recent episode. Those are all aerial insectivores but they're all distantly related. So, in despite Despite the similarity of swallows and swifts, those two groups are very, very distantly related on the bird tree of life. On the breeding ground of the white-throated needle tail, the food that

they eat consists mostly of beetles, like ladybugs, as well as parasitic wasps, small bumblebees, and mayflies. Other things they might eat would be winged ants, you know, at that short time a year when ants have their nuptial flights and they develop wings and fly around and then they get snatched up by swifts and the swifts will also eat flies and moths and basically anything that's flying around that's small and of the right size and has six legs or so needle tails will forage at all different heights from just above the ground in fact they'll even sometimes pick up insects right off the ground or they might be foraging at six thousand feet above the ground These birds also drink in flight

So they'll swoop down low Over a puddle or a pond or lake And they just open their bill And the lower mandible, the lower bill Scoops up a little bit of water And that's how they drink The time of day that they forage Tends to be a bit before sunrise

And a little bit after dark So they're somewhat crepuscular in their behavior Right Cropuscular being active In the early dim light of morning Or the late dim light of evening and if you're in the right place at the right time, you might see thousands of these birds all foraging together, wheeling around over your head, and it's really a spectacular sight.

I mean, I wouldn't know because I haven't seen the species, but I watched some YouTube videos. That's almost the same thing. Okay, and finally, our last section here is to talk about breeding. Now, we talked about the nests of where these guys are. like to breed in large tree hollows and often those hollows are excavated by woodpeckers first and then when the woodpeckers move on then other cavity nesters like swifts can move in the nest itself is inside the cavity and so if you imagine at the bottom of the tree hollow there's a bunch of debris that's accumulated there maybe rotting wood and who knows what else the nest itself is basically just

to scrape just a little depression in that material something like 12 to 20 inches across or 35 to 50 centimeters. And this could be in coniferous trees like larches or in deciduous trees like oaks. So once there are some eggs, both of the parents actually incubate them, and the incubation period lasts for about 40 days. When the chicks hatch, they're blind and naked, so that would qualify them as altricial. And it takes them about 40 to 42 days before they're fledged, ready to fly off. And one of the things about the importance of large tree cavities is that the young birds can actually practice flying inside the tree cavity if it's big enough.

It's a safe space where they can flap their wings and make tiny little short flights from one side of the cavity to the other. Now, I couldn't find any real information on the lifespan of these birds, and that's pretty common. I mean, there are many bird species that we have no idea how long they live, but there is an estimation of generation length in this species at about 3.7 years. And there you have it, the white-throated needle-tail, herandapus catechutus, a graceful, fast-flying bird that migrates long distances and spends most of its life in the air, scooping up countless insects on the wing. Well, thank you for listening to Random Bird Thursday this week. I hope you enjoyed it. Short and sweet, that's how we do it here with Random Bird Thursday. and honestly I couldn't find a whole lot more information about this species to share with you and that's okay we are looking at randomly selected birds learning what we can about them

to expand our knowledge of the avian world I will catch you next time cheers Thank you.