How do birds not crash into each other?

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I’m not talking about geese. I’m talking about those huge flocks of birds. There’s 1000s of them and they never collide with each other. How?

In: Biology

5 Answers

Anonymous 0 Comments

Birds in general have very clear vision that is highly sensitive to motion and their eyes being on the sides of their head gives them incredibly wide ranges of vision. So they just have to not get too close to their neighbors. Really it’s just that simple.

This makes more sense when you realize the movement of those massive groups is not intentional. That is, they aren’t trying to reach somewhere. It is an instinct that protects them from predators by forming a moving mass that makes it hard for any individual bird to get targeted. So really it’s all semi random movements of individual birds translating to big motion of the whole group in an unpredictable way.

Anonymous 0 Comments

The same way people in a big crowd can move in concert without stampeding and crushing each other. And, just like big crowds, sometimes two birds DO bump into each other. But we don’t notice that much.

In a graduate modeling course, our porfessor presented a neat piece of research. We were discussing how in alrge systems it is easy to get seemingly VERY complex behavior out of very simple isntructions (and vice versa, you can model systems with a lot of accuracy with very simple terms sometimes). Roomba (robot vaccuum) were pretty new at the time, and he explained how they could reliably cover every inch of floor in a room with very simple isntructions (if you hit a wall, rotate X degrees and go, if you come to a vertical drop, back up and roatat y degreees and go, if you hit Z number o vertical walls in less than A seconds, back up, rotate B degrees and go… that sorta thing). The roomba doesnt know the size or sdhape of your room. It doesnt keep track of where its been, it doesnt have any radar or machine vision, just a very small set of basic rules. The research he presentd was a guy who wanted to model those big huge flocks of starlings. You can see videos of them, hug flocks of thousands of birds all moving in unified concert like a school of fishes, swooping and curving across the sky. He found that a computer model could accurately predict their motions and interactions with a simple ruleset that was only like 3 limits on bird’s flight (this is going from memory, so likely not accureate, but it was something like):

* stay at least X distance from the closest bird to you
* do not get farther than Y distance from the closest bird to you
* try to keep your direction of travel within ZZ degrees of the direction of the closest bird to you

And that was it. Basically the birds dont need to do anything complex. They just need to keep track of the closest bird to them, stay close (but not too close) to them, and try to fly in generally the same direction as them. If you make a flock of 10,000 birds, and all of them do nothing but follow that basic rule, it’ll look just like one of [these crazy videos](

Anonymous 0 Comments

It’s called “hive mentality” or “group mentality” you see the same thing with large schools of fish when a shark or whale attacks them, they just effortlessly morph in a group out of harms way.

Each individual is aware of their surroundings and in the group they just move based on what is around them (which in the group means other fish or birds) this in turn creates a hive mind where each individual reacts to the individuals around them reacting.

Anonymous 0 Comments

>There’s 1000s of them and they never collide with each other.

They *do* collide with each other. It’s just not a big deal when they do.

When you bump into someone in a crowd, you just instinctively adjust in less than a second and continue on your way. Same thing with birds, bats, etc. It doesn’t significantly disturb their flight path to brush up against another body that is already moving in generally the same direction.

Anonymous 0 Comments

Who says that they don’t crash into each other?