How do birds locate thermals?
Student
Is it just pure luck or speed-to-fly "thinking" ?
Roy Edwards
sounds put out by the thermals
Following on from date
>Is there a consensus on how birds locate thermals?
>
>Is it just pure luck or speed-to-fly "thinking" ?
Tauranga Gliding Club
New Zealands Premier Gliding Site
Compare the costs, compare the value
Where else would you want to fly!
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James W L Clarke
produce ultrasound that can be detected hundreds of miles away. Thermals may
also produce a weak but detectable ultrasonic signal.
Jim Clarke
Institute of Sound and Vibration Research
'JHP'
Roy Edwards wrote in message <37de1ece...@news.wave.co.nz>...
zerocinco
did gulls get them? Do ground dwelling raptors still have them? And how
about swifts? And ravens? From a common soaring ancestor? There wasn't one
as far as I know.
I think raptors learn where to find thermals in much the same way as we do
(with a possible bow towards other sensors). A bird learns his local area
before venturing out further. I have seen them come to the same exact lift
sources over and over to thermal (i.e. my black roof in an oak forest).
Being out in the air covered with feathers is a lot different than being in
a fiberglass tube listening to whistles. Hang glider pilots admit that they
have a lot more sensation of air movement. They can feel the sideways motion
of air entering a thermal at its base.
When I was a student, I thought this was impossible but the more I fly, the
more I realize that I can sense a thermal sooner than the varios by feeling
for it. I imagine that a bird is immeasurably more sensitive to his
environment than I am.
It may not seem that the majesty of Mother Nature could be based upon the
theory that if you fly in a straight line, you will eventually hit a
thermal, but it works for us. If I could get away with a 1/4-knot thermal to
earn my breakfast, my perspective would be more like theirs. They just hit a
lot more lift sources that we do because they can settle for a lot less.
I think Swifts see the bugs or smell the moisture or the odor of the earth.
I think gulls are opportunists. I think ravens are just smart. Many times, I
have seen them sit in the same tree by a highway waiting for a semi to come
along and kick off a dust devil. I wish I had thought of that!
Student
>
> Its certainly plausible. Atmospheric disturbances such as storms and wave
> produce ultrasound that can be detected hundreds of miles away. Thermals may
> also produce a weak but detectable ultrasonic signal.
>
> Jim Clarke
> Institute of Sound and Vibration Research
> 'JHP'
>
> Roy Edwards wrote in message <37de1ece...@news.wave.co.nz>...
> >A recent TV documentary believed that the birds sensed the ultra low
> >sounds put out by the thermals
Ah, ultra low and ultrasonic aren't the same. It's hard to imagine a
generator for 50kHz or greater sound. I find it easy to imagine a
subaudible generator in a thermal. As a former radio direction finding
engineer, I can imagine "ears" with hemispherical coverage and a matched
filter working pretty good. I wonder if ....
Aki Suokas
Even human ears can detect altitude changes (large).
Janusz Kesik
sensitive thermometer?
Janusz Kesik
Poland
lan...@polbox.com
Student napisał(a) w wiadomości: <37DDEA90...@clouddancer.com>...
Sean
lift than their low-time counterparts.
Take these same pilots, put them in the air from dawn to dusk for their
entire lives and allow them full body and sensory exposure to the air mass
(smells, temperature, feeling unbalanced lift on their extremeties, hearing
the sound of air over feathers, seeing low-level bugs at altitude, the
ability to fly at extremely slow speeds, full-body attitude changes caused
by even microlift etc) and I expect they too will aquire an uncanny knack
for finding lift.
Birds may, or may not, have 'special' sensory abilities to find lift but I
would expect they use a more holistic approach than any specific sense. The
bio-feedback they get from their feathers alone gives them an advantage
over those of us who feel the air only through our backside pressure on the
seat...and we are well aware of the advantage of a sensitive 'backside'
over any instrument on the panel.
Sean
--
se...@direct.ca
zerocinco <she...@imdata.com> wrote in article
<rtsq20...@corp.supernews.com>...
Student
>
> I don't fully "buy" the idea of special sensors. If raptors had them, where
> did gulls get them? Do ground dwelling raptors still have them? And how
> about swifts? And ravens? From a common soaring ancestor? There wasn't one
> as far as I know.
If it's a sound, they all have hearing. If you mean some sort of heat
sensor,
I fully agree. If it's the shimmer in the air, they all have pretty
good sight.
> I think raptors learn where to find thermals in much the same way as we do
> (with a possible bow towards other sensors). A bird learns his local area
> before venturing out further. I have seen them come to the same exact lift
> sources over and over to thermal (i.e. my black roof in an oak forest).
I return to the same general area also, but I would do so if I had a
sensor
indicating there was a thermal there too. If they are flying search
patterns
for lift and not food, it would be a pretty big confirmation.
> Being out in the air covered with feathers is a lot different than being in
> a fiberglass tube listening to whistles. Hang glider pilots admit that they
> have a lot more sensation of air movement. They can feel the sideways motion
> of air entering a thermal at its base.
>
> When I was a student, I thought this was impossible but the more I fly, the
> more I realize that I can sense a thermal sooner than the varios by feeling
> for it. I imagine that a bird is immeasurably more sensitive to his
> environment than I am.
Very true. Recently while under spin instruction, it appeared that no
more lift
was available and landing practice was next. As the instructor was
suggesting a
landing pattern beginning with a left turn (which I was just about to
start), I
said "wait a minute", banked right and eventually climbed 2000'. No
vario clues,
but something in the stick or airframe. I have since repeated this
event and
think it comes from 50,000 miles of motorcycle riding making me very
sensitive to
vibrations. Some flights with Hod Taylor had previously convinced me
that I'm
never committed to a turn when searching for lift, so changing direction
was
immediate. I really don't know how I found it, but on that occasion I
knew
something was there.
> It may not seem that the majesty of Mother Nature could be based upon the
> theory that if you fly in a straight line, you will eventually hit a
> thermal, but it works for us. If I could get away with a 1/4-knot thermal to
> earn my breakfast, my perspective would be more like theirs. They just hit a
> lot more lift sources that we do because they can settle for a lot less.
This is a good point and only careful observation just before the bird
enters
the thermal will differentiate between "luck" and "clue". I think that
watching
the bird's head should provide an indication. Clearly a two person job,
I
wonder if there are any grants....
> I think Swifts see the bugs or smell the moisture or the odor of the earth.
> I think gulls are opportunists. I think ravens are just smart. Many times, I
> have seen them sit in the same tree by a highway waiting for a semi to come
> along and kick off a dust devil. I wish I had thought of that!
Glider pilots are smart opportunists? Maybe :) I got a ride in the
Nimbus
4DM the other day and Carl got off to a very low start (no thermals in
the
usually spots). I was practicing picking landing out spots while he
circled
and searched. I'd swear those wings triggered the rising thermal that
showed
up in about 5 minutes.
Gapagod
Consider when the teradactyls first started thermalling, probabally flapping a
lot while they tried to center the thermals. The teradactyls that did not do
so well probably got "dumped" on by the ones that thermalled better. Remember,
they didn't have cars back then for target practice. Heck, isn't that what we
use P bags for?
The ones that got dumped on probably were blinded or at least their CGs were
messed up ( big bird, big...) , and they ended up crashing and were then eaten
by velociraptors or whatever.
So, only the good ones got to procreate and evolve into eagles.
Mike Lindsay
<jw...@soton.ac.uk> writes
>Its certainly plausible. Atmospheric disturbances such as storms and wave
>produce ultrasound that can be detected hundreds of miles away. Thermals may
>also produce a weak but detectable ultrasonic signal.
>
>Jim Clarke
>Institute of Sound and Vibration Research
>'JHP'
>
>Roy Edwards wrote in message <37de1ece...@news.wave.co.nz>...
>>A recent TV documentary believed that the birds sensed the ultra low
>>sounds put out by the thermals
>>
>>
>>>Is there a consensus on how birds locate thermals?
>>>
>>
>>Tauranga Gliding Club
>>New Zealands Premier Gliding Site
>>Compare the costs, compare the value
>>Where else would you want to fly!
>>www.theoffice.net/gliding
>
>
author (Brennig James?) suggested attaching strain gauges to the wing
roots to act as microphones. I don't know if anyone followed up the
idea.
--
Mike Lindsay
zerocinco
Gapagod wrote in message <19990914135625...@ng-ft1.aol.com>...
>I think evolution plays a big part in this.
>
>Consider when the teradactyls first started thermalling, probabally
flapping a
>lot while they tried to center the thermals. The teradactyls that did not
do
>so well probably got "dumped" on by the ones that thermalled better.
Remember,
>they didn't have cars back then for target practice. Heck, isn't that what
we
>use P bags for?
>
>The ones that got dumped on probably were blinded or at least their CGs
were
>messed up ( big bird, big...) , and they ended up crashing and were then
Jim Skydell
ability of tree-top flying birds (pigeons) to sense changes in altitude
using barometric pressure only (no visual cues).
Birds were placed in pressure chambers and heart rates were monitored
for changes in response to very mild electric shocks given just before
changing the chamber pressure up or down. The mild shock would cause an
increase in heart rate, which would take place when the pressure was
changed inside the chamber. This "operant conditioning" made the birds
associate a shock with pressure changes.
Once the birds were conditioned in this way, the shocks were stopped,
but pressure changes continued, to smaller and smaller degrees. A rise
in heart rate indicated that the birds could sense the pressure change,
since they expected a shock at the same time (which never came).
End result: NON soaring birds were able to sense a pressure difference
equivalent to 3 feet up or down.
Birds who then sustained damage to their inner ear mechanisms lost the
ability to sense any pressure change at all, placing the physical
location of the pressure sensing organ in the auditory (hearing) or
vestibular (balance) systems.
To my knowledge, such research has never been carried out on soaring
birds, but one would suspect that their "built-in vario" is even more
sensitive than a pigeon's.
Clearly, humans have no such ability to sense pressure changes, although
with practice, it will become obvious to any glider pilot that one can
sense vertical acceleration. This ability is thought to reside
anatomically in the "butt."
Of course, to prove this, one would have to remove someone's butt, and
see what it did to their thermalling ability...
Jim Skydell DG-300 "8B"
Peter D. Brown
Student wrote:
> Is there a consensus on how birds locate thermals?
My completely uneducated guess is that their ears have evolved into
varios. After all, an ear is somewhat similar, ie a sealed chamber with
an opening to the outside.
As a bird is rising, air will flow from the "chamber" near the eardrum
to the outside area of lower pressure. Do they hear it or feel it? ... I
have no idea.
This is not unlike our own ears which pop when we climb or descend. Its
not too much of a stretch to see how this ability would have conferred a
significant advantage to those soaring-like birds that use thermals as a
partial substitute for calories for energy.
Pete
Sean
Jim Skydell <sky...@prodigy.net> wrote in article
<37DEEDC5...@prodigy.net>...
>>...Of course, to prove this, one would have to remove someone's butt, and
Gapagod
>see what it did to their thermalling ability...
I know some people who had this operation...only they left the butt!
Jim Husain
gap...@aol.com
Wilhelm Holtmeier
> Of course, to prove this, one would have to remove someone's butt, and
> see what it did to their thermalling ability...
In the case of some people I know next to nothing would be left. ;.)
--
Blue skies!
Wilhelm Holtmeier
PGP ID 0x5DBFFD54
http://www.trustcenter.de/cgi-bin/SearchCert.cgi
Gary Boggs
> Of course, to prove this, one would have to remove someone's butt, and
> see what it did to their thermalling ability...
>
I got my butt chewed a few times when I was still a student, but never
completely off. I did seem to help my thermaling.
John M. Morgan
Gary Boggs < gbo...@hevanet.com> wrote in message
news:01beffbb$100ce3c0$6a3c77cc@gboggs...
> I got my butt chewed a few times when I was still a student, but never
> completely off. I did seem to help my thermaling.
>
Don't birds locate thermals by watching for circling sailplanes?
bumper
Robert W. Cunningham
No, that's how thermals decide to trigger...
-BobC
Bert Willing
"John M. Morgan" wrote:
> Don't birds locate thermals by watching for circling sailplanes?
>
> bumper
Jung birds actually do that in autnum when they have their first trials. I once
played around on a local flight with a couple of them.
As they become more experienced, they eventually come to know about us ....
--
Bert Willing
-----------
Caproni Calif A21S D-6600
Come fly at La Motte du Caire in the French Alps:
http://www.decollage.org/la_motte/
Lars Peder Hansen
Bert Willing wrote:
> "John M. Morgan" wrote:
>
> > Don't birds locate thermals by watching for circling sailplanes?
> >
> > bumper
>
> Jung birds actually do that in autnum when they have their first trials. I once
> played around on a local flight with a couple of them.
>
> As they become more experienced, they eventually come to know about us ....
- And they then figure out where to look for the _really_ good thermal: A few hundred
meters from the circling sailplane..
Lars Peder
--
_________________________________________________________________________
Lars Peder Hansen
Denmark branch of The Global Village.
mailto:l...@post1.tele.dk
Phone, Work:(+45) 87310700 Home:(+45) 86523988 Mobile:(+45) 40350870
_________________________________________ I'd rather be soaring... __________
"Quality is the common ground for art and technology"
Brett Rabe
>
>
> Don't birds locate thermals by watching for circling sailplanes?
Yup. Then they go fly a few hundred yards away
from the sailplane where the thermal actually is.
Brett
--
Brett Rabe br...@uswest.net / 612.664.3078
ISE U S WEST - Internet Services
Age is a very high price to pay for maturity.
James W L Clarke
'infrasound' not ultrasound which is the frequency range I normally work in.
Infrasound is very low frequency <20 Hz and atmospheric turbulence is
certainly a possible generation mechanism.
Jim Clarke
Institute of Sound and Vibration Research
'JHP'
James W L Clarke wrote in message
<7rlb1v$p04$1...@chestnut.sucs.soton.ac.uk>...
James W L Clarke
atmospheric turbulence is definitely a possible generation mechanism.
Jim Clarke
>
>
mike_th...@my-deja.com
thermals, I was easily able to outclimb vultures in South Africa in my
Jantar-1. In the more usual stronger, smaller thermals, it was the
other way round, but I was only outclimbed because of the birds' ability
to locate small pulses of lift and turn rapidly. Pressure-change is, in
my opinion, the only mechanism that will work to sense such small rapid
changes. There is plenty of research that has confirmed birds' pressure
sensitivity.
Temperature differences are too small because of mixing of the thermal
with the surrounding air - despite their name, thermals aren't
measurably warm.
The remaining question is whether or not birds have other senses that
help locate thermals. Many birds have excellent senses of smell, and
thermals do raise small amounts of material from the ground. This last
weekend, even I located a thermal that had pulled in smoke from a grass
fire - at 5,000 feet above ground, the smoke smell was right in the
strong lift.
Finally, there are small, but detectable, differences in electrical
charge and ionic content in thermals compared to the surrounding air.
Mike Stringfellow
ASW-20 WA
Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't.
norbas
Once upon a time, a sympathetic stork saved my 5 hour flight.
I was about to land at 4.50 h... and a bunch of storks showed me the way for
about ten minutes...in close formation.
Novice as myself, i think :-)
Norbas
M
answer let me know.
Ockham's Razor - "the mind should not multiply entities beyond necessity.
What can be done with fewer ... is done in vain with more."
I just knew that some day all thoes years in graduate school would come in
handy.
Michael Neal
signs such as rising dust, other birds, bugs, area knowledge, etc., etc.,
...
I have flown R/C gliders for years, in high performance thermal duration
competition, scale thermal, slope, etc. Flying R/C gives you a unique
ability to see the "small details" of thermal development that are missed by
full sized aircraft. In fact my performance R/C glider is nearly identical
in size to that of the majority of the raptor species. Therefore our
performance is quite similar.
The areas of California that I fly in are rural areas with large raptor
populations. I cannot count the number of times when I have launched my
glider on a marginal day and happened upon an isolated but good thermal. It
is amazing how quickly a group of several hawks and / or buzzards will join
you from their resting place in the trees. It is actually quite humourous,
you can almost hear the thoughts of the birds as first one then more join
your circling aircraft:
Sitting in a tree; "Hmm, that strange looking buzzard over there just
started cicling, wonder if he's got something? I'll wait a minute and see if
he makes any gains."
A few turns later, and if I'm going up, out he comes to join me. A short
time later a few of his friends decide that if we're both going up, it may
be worth the effort to try too, soon enough your in a gaggle.
What's pertinent to this discussion is that I have often caught thermals
within 50 yards or less of the hill and trees where these birds are sitting
waiting for some action. It seems to me, and this is pure conjecture on my
part, that if a raptor had the capability to sense sub-sonic air density
changes, they would have known and flown to the thermal before I found it.
There is no doubt that the birds are looking for flying oppertunities, as I
have seen them leave their roosts at the first hint of a themal, or on
viewing other birds, including our R/C gliders flying.
There is no doubt also that they are in much greater "tune" to the
surrounding air and can core out a thermal much more efficiently than I can.
But as far as finding thermals are concerned, I'd say that they use the same
indicators as we do.
$.02 Paid in full.
Michael N.
zerocinco <she...@imdata.com> wrote in message
news:rtsq20...@corp.supernews.com...
> I don't fully "buy" the idea of special sensors. If raptors had them,
where
> did gulls get them? Do ground dwelling raptors still have them? And how
> about swifts? And ravens? From a common soaring ancestor? There wasn't one
> as far as I know.
>
> I think raptors learn where to find thermals in much the same way as we do
> (with a possible bow towards other sensors). A bird learns his local area
> before venturing out further. I have seen them come to the same exact lift
> sources over and over to thermal (i.e. my black roof in an oak forest).
>
> Being out in the air covered with feathers is a lot different than being
in
> a fiberglass tube listening to whistles. Hang glider pilots admit that
they
> have a lot more sensation of air movement. They can feel the sideways
motion
> of air entering a thermal at its base.
>
> When I was a student, I thought this was impossible but the more I fly,
the
> more I realize that I can sense a thermal sooner than the varios by
feeling
> for it. I imagine that a bird is immeasurably more sensitive to his
> environment than I am.
>
> It may not seem that the majesty of Mother Nature could be based upon the
> theory that if you fly in a straight line, you will eventually hit a
> thermal, but it works for us. If I could get away with a 1/4-knot thermal
to
> earn my breakfast, my perspective would be more like theirs. They just hit
a
> lot more lift sources that we do because they can settle for a lot less.
>
Nyal Z. Williams
Peter D. Brown wrote in message <37DF08CD...@gci.net>...
snip-
>My completely uneducated guess is that their ears have evolved into
>varios. After all, an ear is somewhat similar, ie a sealed chamber with
>an opening to the outside.
>
>As a bird is rising, air will flow from the "chamber" near the eardrum
>to the outside area of lower pressure. Do they hear it or feel it? ... I
>have no idea.
>
>This is not unlike our own ears which pop when we climb or descend. Its
>not too much of a stretch to see how this ability would have conferred a
>significant advantage to those soaring-like birds that use thermals as a
>partial substitute for calories for energy.
This notion was advanced by Philip Wills back in the early '50s in his book
"On being a bird."
bz
>As a bird is rising, air will flow from the "chamber" near the eardrum
>to the outside area of lower pressure. Do they hear it or feel it? ... I
>have no idea.
>
Either way 'Le Petomane' would make this bird think it was in sink.
Colin
I forecast a glorious convergence of two threads....
SoarStan
thermals; by team flying. Certain cranes which migrate from somewhere in
central Europe, all fly the same thermal. As each bird tops out, it flys out on
general course, but just slightly different than the guy who just left. The
result is a fan of birds, spreading out over a larger and larger volume of sky.
Then as soon as one bird begins to circle, they all make a bee line for him, or
her!
Simple, aint it?
Steve Barter
SoarStan <soar...@aol.com> wrote in message
news:19991005233553...@ngol01.aol.com...