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Paraglider and hang glider pilots can also soar for hundreds of miles without power or flapping. Soaring birds like condors, turkey vultures, hawks, etc. use the same technique of turning in tight circles in rising air to increase altitude. Once cloud base is reached and the rising air stops, they glide significant distances to the next hillside with rising air. Whenever you see birds in the sky circling around the same spot together, it's because they're in rising air and using it to stay aloft.

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“He spent a lot of time flying. He learnt to communicate with birds and discovered that their conversation was fantastically boring. It was all to do with wind speed, wing spans, power-to-weight ratios and a fair bit about berries. Unfortunately, he discovered, once you have learnt birdspeak you quickly come to realize that the air is full of it the whole time, just inane bird chatter. There is no getting away from it.”

― Douglas Adams, Life, the Universe and Everything

> just inane bird chatter

I suspect most bird chatter is about sex, not flying.

Like when you're out in the summer evening, and the crickets are chirping and the frogs are croaking, and you realise it's just a whole bunch of males shouting "hey baby, over here!"

Service discovery all the way down.

In a lot of species the females are the one making noise, sloths and snow leopards as a couple of examples.

I got a bird feeder a little while ago. After watching them closer that I had in the past, I realized something. All that chirping going on either means "Have sex with me" or "Go away, this is mine."

All the chirping I had ever heard basically means the same thing as most of what my peers were saying in junior high.

> It was all to do with wind speed, wing spans, power-to-weight ratios and a fair bit about berries.

As much as I like Douglas Aadms, this statement is just wrong. A lot of bird chatter is songs to demarcate territory, threat warnings, contact calls to maintain flock awareness, young birds saying 'feed me', and others.

I know when a cat has entered my garden by the clucking warning calls that the blackbirds make. They make a different warning noise when I interrupt them on my bird feeder. Sometimes I'm alerted to a buzzard by the calls of rooks who are ganging up on it.

It might be a mistake to read Adams for scientific accuracy.

Next you'll be telling me that I can't fly even after I forgot about gravity.

I'll float around your head for hours just to prove you wrong!

One could write a lovely poem about that.

Yeah, true. But I've seen three bird calls that don't fit that pattern in my garden. Long tail tits seem to move around in small flocks, probably eating the insects in my trees. Every few seconds one of the flock flies to another tree. If the others don't follow, it flies back. While this is happening there is a constant chorus of little chirps. My guess is that they feel "attracted" to the centroid of the chirps, as a simple, almost mechanical way to keep the flock together (its hard to see each other amongst all the branches).

The other case is juvenile magpies. As adults I mostly hear them shouting aggressively at each other. But if the youngsters don't know I'm there, I've sometimes heard them chatting. The sounds they make are complex and quiet. A bit like this https://www.youtube.com/watch?v=8P4ZVgjslVQ but I've always seen them in pairs or groups when doing this.

Third is the Robin (European). They also have a whisper song. Sometimes they do it so quietly that I have to be within a few feet to hear it. And there's no other bird around. I guess it's a male who is just working on new material to impress the ladies with later.

I recently had a finch(i think) nest underneath my window AC unit and one of the parents caught a cold for about one week. I heard more calls from that specific bird throughout the time, it was much squeakier while making what sounded like normal calls. It made me think that they relay info on frequencies that our ears dont tune into. Just a hypothesis, but was interesting to hear more inbetween sounds that the other birds didn't make. Could also just be a sort of mask for birds, a call that says 'hey Im sick stay away.' Although I think it'd be obvious for them from the change of voice. Overall it was interesting to listen to them communicate with their young ones. The nest is constantly chirping unless they get warning calls then it gets super quiet until their folks let them know danger has passed. It was unfortunate when I had to replace the unit, at least I waited for the young ones to start flying. My new unit is half the size and they disliked the new roof I tried building to mimic the size of the old one. I wish them luck. Tough little fellars.

Come on people, it is Douglas Adams. You don't read Douglas Adams and think, "Well, technically..."!

Nominating this for the most HN comment of the day

Sorry to have to break the news to you, but the quote is from a work of fiction.

We apologize for the inconvenience.

You might have preferred his description of Kakapo-speak in Last Chance to See then

> “The booming [mating call] is deep, very deep, just on the threshold of what you can actually hear and what you can feel. This means that it carries for very great distances, but that you can’t tell where it’s coming from. If you’re familiar with certain types of stereo setups, you’ll know that you can get an additional speaker called a sub-woofer which carries only the bass frequencies and which you can, in theory, stick anywhere in the room, even behind the sofa. The principle is the same: you can’t tell where the bass sound is coming from.

> The female kakapo can’t tell where the booming is coming from either, which is something of a shortcoming in a mating call. “Come and get me!” “Where are you?” “Come and get me!” “Where the hell are you?” “Come and get me!” “Look, do you want me to come or not?” “Come and get me!” “Oh, for heaven’s sake.” “Come and get me!” “Go and stuff yourself” is roughly how it would go in human terms.”

Excerpt From: Douglas Adams & Mark Carwardine. “Last Chance to See.” Apple Books. https://books.apple.com/us/book/last-chance-to-see/id4608191...

(I once emailed Adams asking when this book would be published in paperback, this was back when the Internet was small enough that one could sleuth and guess nearly anything. He responded three years later, saying that Random House had published it with "the worst cover I've seen in my career.")

Seconding his book Last Chance to See, it is a fantastic travel/nature book with all the usual Douglas Adams flare.

There's thermals (a spot on the land that is warmer than the surroundings so the air rises there), and there's topography that causes rising air (for example when the wind blows at a face of a hill - the air has no choice but to go up).

RC gliders can stay in air basically forever flying back and forth in rising air along a hillside. It's called slope-soaring and it's great fun.

> RC gliders can stay in air basically forever flying back and forth in rising air along a hillside.

And there's been some effort to have autopilots do it automatically https://ardupilot.org/plane/docs/soaring.html

Somewhat more impressively, albatrosses do that on the forward faces of waves, soaring for days far away from thermals and hills.

There's research that they use dynamic soaring more, getting energy from the different wind speeds at sea level and a bit above https://www.youtube.com/watch?v=uMX2wCJga8g

Gotta love the end of the video aha! But the whole video is very interesting. As a kayaker myself I can definitely “feel” the phenomenon they are talking about of extracting energy by alternating on two sides of a flow gradient.

Next up in kayagliding...

That is very interesting. I always assumed sea birds used combination of wing in ground effect [1] and the lift of wind hitting the front of waves to cover long distance, but this explanation makes much more sense for birds crossing oceans.

[1] https://www.youtube.com/watch?v=vkVVnx70FgI

Edit: It just occurred to me that the albatross is in some way surfing the wind in much the same way a surfer pumps along a wave to generate speed.

Here's an RC glider doing 545 mph with that technique: https://youtu.be/MoaWlKC3wIM

I don't know how they manage to control it or measure the speed, but it looks legit.

Wow. That's not how it usually looks like :)

Usually it's very slow and relaxing. Looks like this:

https://youtu.be/Ev5fSVi1PrA?t=152

That is dynamic soaring [1] which is I guess a subset of slope soaring, and is pretty rare and nuts. It generally requires flying in the lee of a slope rather than in front of it.

Regular slope soaring is relatively more sedate, fun and accessible if you have the right slope.

[1] https://en.wikipedia.org/wiki/Dynamic_soaring

> Dynamic soaring is sometimes confused with slope soaring which is a technique for achieving elevation.

> RC gliders can stay in air basically forever flying back and forth in rising air along a hillside. It's called slope-soaring and it's great fun.

This was my thought also. The Andes Mountain Range are rather mountain range right next to the ocean. I would think that is a pretty ideal place for a bird to slope soar for a long distance.

Neal Stephenson's Seveneves has a part (part 3) of the book that is set in the distant future. One plot point there is some kind of advanced glider basically exploiting the atmosphere to pick up enough energy over the course of a day to eventually get enough mass (by picking up water) and energy to eventually travel at high speeds & altitudes half way across the planet. Science fiction of course but he has a way of making this somewhat plausible.

Gliders sometimes use water ballast to store more energy so they can stay up longer. Basically after getting towed to an initial altitude they use thermals and ridge soaring to gain altitude. After that it's all about converting altitude to speed and distance based on their glide ratio. Having a high mass apparently helps. Hopping from one lift producing area to another, you can cover great distances.

Currently this is pretty much a recreational activity because you are dependent on weather, sunlight, and other things that are hard to predict and detect. But kind of intriguing notion what you could do if you had a way to reliably find areas with good lift.

On a related note, here's a youtube channel of a glider pilot in Kansas that regularly posts awesome footage from his glider. Here's some awesome footage of him exploring some mountains and exploiting available lift from winds hitting the rocks: https://www.youtube.com/watch?v=Bcd5Z46RGRU

If you want to play about with gliders yourself the sim Condor Soaring is pretty awesome and has VR support. It's a much more chill and relaxing experience than flying combat sims all the time and more engaging than most non-combat sims.

The point about water ballast is actually not entirely accurate - it's not to stay up longer, it's to increase speed. Gliders have a certain angle of attack at which they fly most efficiently (optimal glide angle, i.e. trading the least height for every meter forward). If you add water ballast, the speed corresponding to that angle of attack is increased. The downside is that your downward speed also increases - so when the weather gets difficult or thermals get weak, pilots dump the water.

> The downside is that your downward speed also increases

You're saying the down component of the velocity vector also increases with the velocity itself. Not that heavier objects fall faster, which we know to be untrue from Galileo's famous experiment. I think you understand that, but I thought I'd clarify it.

No you're wrong. Galileo's experiment doesn't apply here. Heavier objects DO fall faster at terminal velocity. A glider in sustained flight is an example of that.

Galileo just showed that objects accelerate at the same rate due to gravity. But they do NOT fall at the same rate unless in a vacuum.

You're right, I didn't think about the difference in terminal velocity.

The rising air doesn't actually stop at cloud base, but it becomes very hard to orient because you don't see the horizon anymore. The thermals can also be generated by many different landscape features - they can be triggered by hills (which can also help them release) but there are plenty on flat landscape as well. Also other sources of upward air currents can be used for soaring, e.g. wind deflecting upwards over a hill or waves high in the atmosphere (search "wave soaring" on youtube). There is even https://perlanproject.org/ aiming to do this at 30km altitude.

If anything it is often the strongest at the base of the clouds from experience.

The top of the cloud is where it stops climbing.

The other reason gliders stop at the cloud base is that it's illegal to fly close to the clouds in most airspace. Because it makes it very hard to avoid collisions.

Good point. I oversimplified. Birds and pilots tend to not fly up into clouds for visibility reasons but the air keeps rising into the cloud. From experience, it's a surreal experience riding a thermal up into a cloud in a paraglider. Just not safe or legal in most places to stay in the cloud.

Paragliders and hang gliders are still easily beaten by sailplanes. World's record for a single day sailplane flight is 3000km (1800mi), that's been performed on mountain lee waves.

FWIW, the estimated glide ratio of a South American Andean Condor is ~ 12:1 or about what a competition Paraglider does. (Or an old hang glider)

I pass a couple bald eagle nests commuting by bike along the river in Minneapolis. I'm always surprised when I see the eagles flapping their wings, since most of the time they are soaring.

Exactly. The condor (or paragliders) can fly that way only in the Andes, because only there it is possible. Over the Amazon for sure not. It's not the bird, it's the environment.

This knowledge is used by glider pilots to identify thermals - let the birds do the hard work and then go copy them!

Those gliders with huge wingspans and no awkward propeller on the nose look incredibly elegant. There's a gliderport not too far from me and I've always wanted to give flying one a stab. But it's really hard (and nerve wracking, lol!) to conceptualize how they stay in the air using thermals. Especially in staying in control when coming in for a landing.

From what I understand, most glider clubs are always looking for new members. Maintenance of the winch, gliders and landing strip is expensive and more members means sharing the costs. One in my province has "introduction days" where you can sit in a two-person glider, in front of an instructor, for a small price or even free.

I think you should just go for it - many gliding clubs have introductory or passenger flight options. I flew gliders for a few years and it's really wonderful - it's very quiet and the view is fantastic. Landing is suprisingly easy most of the time - when people fly "cross-country" (long distances, away from airfields) it's actually common procedure to "land out". Which is basically the same as an emergency landing (e.g. in a farmer's field) but much less stressful because gliders are actually designed to fly well without a functioning engine.

As others have said, go try it out with an experienced pilot/instructor! It's very accessible.

You might be more comfortable in a motor glider - they have enough thrust to conduct their own takeoff and get you out of trouble but are still light enough to glide effectively.

It definitely works the other way, too. When the thermals are weak the vultures in Himalaya, wait until the gliders are climbing and only then go join them.

I had no idea that people can hang glide for hundreds of miles! That’s genuinely amazing.

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