
Evidence that birds sleep in mid-flight - Mz
http://www.nature.com/articles/ncomms12468
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computator
I'm reminded that we still don't know conclusively what purpose sleep
serves[1]. We know about things unimaginably distant in scale or time -- like
quarks and the Big Bang -- but we don't know the answer to something seemingly
pedestrian.

[1]
[https://en.wikipedia.org/wiki/Sleep#Functions](https://en.wikipedia.org/wiki/Sleep#Functions)

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sdegutis
It's meant to separate days. That way each day is a new day, and you have some
sort of mental partition between each one.

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empath75
meant by who?

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sdegutis
Whoever you want.

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ch4s3
I looks like they're referencing this paper[1] which suggests that like
dolphins, birds can sleep 1 brain hemisphere at a time. That's pretty
interesting.

[1][http://www.nature.com/nature/journal/v397/n6718/full/397397a...](http://www.nature.com/nature/journal/v397/n6718/full/397397a0.html)

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yareally
Ducks do that while sleeping. If you observe ducks sleeping near a pond you'll
typically see them sleeping with one eye open and one shut. That way they can
still stay alert enough to watch for predators.

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dmcginty
I've had several pet birds and I've observed the same thing from them. I just
assumed they were just pretending to sleep.

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yareally
Your comment made me wonder how common it is with birds and it seems to be
trait shared with all of them[1]. Pretty interesting. I asked my friend if her
bird does that and it only seems to when it's not in a deep sleep yet, but
eventually it will close both eyes.

[1] [https://en.wikipedia.org/wiki/Unihemispheric_slow-
wave_sleep](https://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep)

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throwaway98764
Gives a new meaning to the term, "sleep with one eye open at night." :)

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glandium
Let me venture a guess: that expression comes exactly from observing animals
keeping one eye open.

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supahfly_remix
> On land, birds can switch from sleeping with both hemispheres simultaneously
> to sleeping with one hemisphere at a time in response to changing ecological
> demands17,18. During such unihemispheric slow wave sleep (USWS) birds keep
> the eye connected to the awake hemisphere open and directed toward potential
> threats.

This reminds me of the low-power sleep states of PCI (L0s, L1, etc.) or a
multicore CPU

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Terr_
I wonder if it correlates with flocking behavior: More individuals makes it
less risky to have a blind-side.

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idlewords
We really need to figure out what sleep is for. It seems important.

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empath75
[https://www.nih.gov/news-events/news-releases/brain-may-
flus...](https://www.nih.gov/news-events/news-releases/brain-may-flush-out-
toxins-during-sleep)

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24gttghh
So, the brain is an electro-chemical engine, and like other engines, it must
be shut down to perform regular maintenance so the engine lasts longer, and is
less prone to error conditions.

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jacobolus
Not just the brain, but the whole body.

If I go without enough sleep, my hair and skin start getting greasy, my immune
system is weakened, my muscles start feeling tired, etc.

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Retra
Your hair and skin get greasy because you aren't bathing, not because you
aren't sleeping.

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jacobolus
You are incorrect, as you can trivially verify yourself with a few days’
first-hand observation.

Even if you don’t bathe at all for a few days, or just rinse yourself with
water (skip the oil-stripping soap for this experiment), the greasiness of
hair/skin fluctuates noticeably throughout the day, and increases
substantially after a day or two of insufficient sleep. (That’s right, the
greasiness will go up and then subsequently go down, without your doing
anything special in between.)

[Side note: it’s pretty disappointing when people make confident sounding
assertions about things they clearly don’t know anything about and didn’t
bother to do the tiniest trivial bit of study. I find this happens quite
commonly even in discussion venues where there’s ostensibly a cultural value
placed on reasoning and evidence.]

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debatem1
I've been sleep deprived for extended periods before and never noticed the
difference. Is there sample size > 1 evidence for this you're aware of?

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rukuu001
I'm currently reading Where Song Began[1] which discusses this, and is super-
interesting besides. Has an anecdote of WW1 pilots encountering flocks of
dozing swallows at night.

1\. [https://www.amazon.com.au/Where-Song-Began-Australias-
Change...](https://www.amazon.com.au/Where-Song-Began-Australias-Changed-
ebook/dp/B00KYDSKXW)

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k_sze
Just me or the fact that they managed to record the brain activity of birds in
flight seems more interesting than the fact that birds sleep in flight?

I mean, the reason I clicked the link is because I wanted to learn _HOW_ they
recorded the brain activity.

I just never imagined EEG sensor + logger can be miniaturized to such a
degree.

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petra
Is it possible for a human(for example a meditator) to learn to sleep with one
eye open ?

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Mz
Yes. My son used to sleep with one eye open. After serving in Vietnam, my
father habitually napped with both eyes open.

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Someone
That seems to imply that the unconscious part of the brain still can use
visual input while the 'mind' is sleeping (just like it can 'read' the output
of your ears, so that it can wake you when your alarm clock rings)

Does anybody know whether that is true? Similarly, does the knee reflex work
when humans are sleeping?

Edit: on the knee reflex, there's
[http://ajplegacy.physiology.org/content/68/2/345](http://ajplegacy.physiology.org/content/68/2/345).
Paywalled, but the knee reflex seems diminished/absent during sleep.

Edit 2: quite surprising, as the knee reflex is so fast that a nerve signal
cannot travel to the brain and back within its response time (and of course,
there's the spinal cat, that walks on a treadmill after its brain has been
disconnected from its spinal cord
([https://en.wikipedia.org/wiki/Spinal_locomotion)](https://en.wikipedia.org/wiki/Spinal_locomotion\)))

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drdeca
I don't know, but I would suspect that doing the knee reflex thing with
someone asleep would often cause them to wake up?

But, also, I think I heard that the signal doesn't get all the way up to the
brain before the signal to kick or whatever starts going down? (I am unsure of
this though.)

So, I would think that the brain being like it is when the person is asleep
wouldn't stop the kick reflex thing, because the brain isn't even what causes
the kick reflex thing?

So my guess is that they would kick and then likely wake up.

I'm not certain of this though. Please correct me if I am wrong.

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sp332
Yes, the reflex is controlled by the "dorsal root" ganglion, at the spine.

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duaneb
Perhaps sleep is a full body affair.

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gweinberg
Kind of OT, but does anyone happen to know if a person with a severed corpus
callosum can sleep with one hemisphere at a time?

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mattbgates
It would make sense that birds do fall asleep while flying, as they are
sometimes prone to fly into buildings or windows that were obviously visible.

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ara24
wow, birds can auto-pilot.

if two halves of the brain can work independently, wouldn't there be a sync
problem! I wonder how the brain handles it.

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prmph
Sometimes I can hear myself lightly snoring while asleep. Its kind of weird

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idlewords
I wonder if they have that "I'm falling" dream and then wake up.

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gnashville
I think that's actually unique to primates (who do/did sleep in trees).

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totalZero
Personally, I always have trouble sleeping while flying.

