Circling for rodents?

Uri Saovray wrote:
Yes, but could you hear their varios beep?


Don't be silly, have you ever seen a bird carrying batteries?

Rgds,

Derrick Steed

Take a look at Darryl Stinton's book "The design of the aeroplane" - there
is a captioned picture in the front of it showing a gull (an Albatross, I
think) soaring a cliff in front of the camera. The caption points out
aerodynamic function of various parts of the birds anatomy in a most
enlightening manner! I don't have the book in my possession right now (I
loaned it to the CFI of a local club, I should get it back I suppose) or I
would post the picture and it's caption.

Rgds,

Derrick Steed
On 4 Jul 2004 20:39:04 GMT, Andy Blackburn
wrote:

Any bird experts out there?

While still in India I met a German lass who was an ornithologist and
in India do a PhD on vultures. Naturally, I asked her about their
flight performance. She just looked at me like I was a dinosaur: she
knew nothing and cared less about their flight performance or
operating methods. All she was interested in was stuff like population
densities, diet and their behaviour when not flying. I found her
attitude most odd.

That was 25 years ago so things, hopefully, might have improved in
ornithological circles.

So, pick your bird expert carefully before asking about how birds fly.

BTW, a good book about flight in general (literally from insects to
747s) is 'The Simple Science Of Flight' by Henk Tennekes. It won't
tell you how raptors find lift but has a good analysis of how flying
creatures size and weight affect their way of making a living and vice
versa. Besides, any book on flight that can sensibly show everything
from a Monarch Butterfly to a 747-400 on the same graph can't be all
bad!

Our understanding of the reason/s for a bird’s excellent
soaring ability continues to be severely hampered by
the lack of progress in establishing verbal communications.
Perhaps a species that can fly through a thicket and
sleep on a branch do not consider it worth their time.



At 20:54 04 July 2004, Andy Blackburn wrote:
Stress, or G-loading, is a measure of acceleration.
As such it allows birds (or pilots!) to sense changes
in the rate of climb, but not the climb rate itself
(which we all know is a velocity, not an acceleration).
I would imagine that birds can use these changes in
acceleration to help find the center of a small thermal
in some cases, but it might be less helpful in larger,
more uniform bands of lift where the ability to integrate
the cumulative acceleration effects over time is more
difficult.

A falconer at the Parowan regionals last week told
us that soaring birds have sensory organs that are
able to measure the pressure differential between the
outside air and inside their hollow bones. I have not
been able to confirm this, but it would seem to make
sense - think of the bones as capacity bottles.

Any bird experts out there?

9B



At 19:48 04 July 2004, Martin Gregorie wrote:
On 04 Jul 2004 18:48:04 GMT, ospam
(Frostowits)
wrote:

Pardon this input from an uninformed intruder to this
subject, but why couldn't
birds simply sense how strong the lift is by the amount
of stress it puts on
their 'airframe'. When I pump iron, I'm all too aware
of the amount of effort
required. Surely birds can do the same.

Some seem to do just that. Kites in particular. I used
to watch them a
lot in India and discovered that you can tell how strong
the lift is
by looking at them - the stronger it is the more dihedral
they use. If
its really strong they just bomb round with a steep
V-form and their
tip feathers closed. Weaker lift gets more care and
attention, less
dihedral and more open tip feathers. When they're really
scratching
their wings are flat or even a little anhedralled and
the tip feathers
are fully spread and up to give tip dihedral. They
initiate a turn
with a big dab of negative in the inner tip and then
control the turn
on tail tilt - the outer tail tip is raised, so you
can tell that
they fly like we do with down force on the tail. Kites
are easy to
read because they often work low altitude lift where
you can see
exactly what they are doing and have big, long tails
that are easy to
observe.

I wondered about how vultures fly but they were so
seldom low enough
to really watch that I couldn't work out very much.
Also, with much
shorter tails than kites its difficult to see whether
they use tail
tilt at all or which way its applied.

The above is about all I know about soaring birds:
I'm no
ornithologist or naturalist. My background is chemistry,
competitive
free flight model flying and, latterly, soaring.

I've heard a number of theories about how birds detect
thermals
including that they hear them. I'd well believe that,
with a nerve on
each feather, they must *really* feel the air and all
its
micro-turbulence. Maybe they can hear it too. However,
that tells
something about how they work 'normal' thermals but
not a lot about
how they can find and work the very weak, smooth lift
you get early
and late in the day. We know that migratory birds have
a excellent
directional sense so why shouldn't a soaring bird have
a built-in
vario too? I'd love to know how it works.

If you haven't read it, find a copy of Philip Wills'
'On Being A
Bird'. There's a chapter about flying with vultures
in South Africa
and how he worked just how vultures operate - altitudes,
spacing, food
finding strategy etc. The whole book is a good read
too.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

Darwin would say the ones that didn't thermal too well didn't
survive, didn't reproduce, and simply missed out on some good
airtime for generations to follow. The birds that acquired the
insight to locate updrafts gained the same advantage we seek: xc
distance. Soaring birds are usually larger than others, maybe good
thermaling skills means better meals. They still need to survive
winters with fewer, weaker thermals by other means.

gill
www.gillcouto.com


Uri Saovray wrote:
Does anyone have an idea of how the birds know where to thermal? Do
they have a vario? Where is it? Where is its capacity?
Assuming they breath while thermalling, then I doubt they use their
lungs as capacity... or maybe they stop and sense the air coming out
their noses.
Just wondering...

Uri 4XGJC

I'm also convinced that birds soar for pleasure as well as because they
might have to

Earlier this year sitting in my garden on a hot windless day, I watched a
Buzzard pick up a thermal over a small local wood and climb until it was a
speck in the sky. It then closed its wings and dived at great speed until it
was about fifty feet above the ground, pulled out and then proceeded to
climb again. It repeated the climb, dive, climb manoeuvre three times before
I went indoors. Surely that could not have been for anything other than
pleasure ?

DB

More likely it was stooping for prey which moved to
cover or perhaps a mating display. (Showing off, nothing
new there then :-))

Most birds of prey (owls excepted) use thermals as
a source of free energy to be able to observe prey.
Captive birds of prey will not fly if they are 'not
hungry', in need of food and if they eat and become
over a certain weight flight becomes difficult or even
impossible for them. (Anyone know the maximum all up
weight of a swallow)

At 09:12 05 July 2004, Silent Flyer wrote:


I'm also convinced that birds soar for pleasure as
well as because they
might have to

Earlier this year sitting in my garden on a hot windless
day, I watched a
Buzzard pick up a thermal over a small local wood and
climb until it was a
speck in the sky. It then closed its wings and dived
at great speed until it
was about fifty feet above the ground, pulled out and
then proceeded to
climb again. It repeated the climb, dive, climb manoeuvre
three times before
I went indoors. Surely that could not have been for
anything other than
pleasure ?

DB

"Don Johnstone" wrote in
More likely it was stooping for prey which moved to
cover or perhaps a mating display. (Showing off, nothing
new there then :-))

As Buzzards are carrion eaters I doubt if it was chasing it very far.

John

Sorry to be pedantic, but not exclusively, Buzzards
can and do take live coneys and rats, I have witnessed
them doing so. Are you sure you are not confusing them
with Kites which are almost exclusively carrion eaters.


At 12:36 05 July 2004, J.M. Farrington wrote:

'Don Johnstone' wrote in
More likely it was stooping for prey which moved to
cover or perhaps a mating display. (Showing off, nothing
new there then :-))

As Buzzards are carrion eaters I doubt if it was chasing
it very far.

John

"Silent Flyer" ] wrote in message ...

I'm also convinced that birds soar for pleasure as well as because they
might have to

Earlier this year sitting in my garden on a hot windless day, I watched a
Buzzard pick up a thermal over a small local wood and climb until it was a
speck in the sky. It then closed its wings and dived at great speed until it
was about fifty feet above the ground, pulled out and then proceeded to
climb again. It repeated the climb, dive, climb manoeuvre three times before
I went indoors. Surely that could not have been for anything other than
pleasure ?

DB

Definitely not. I have watched similar behaviour many times. One
particular time I was climbing under an nice fat cu where three
buzzards were climbing in to the cloud out of sight and then diving
out of it about five seconds later, over and over again.

Marcel
-------------
Why walk when you can soar?

impossible for them. (Anyone know the maximum all up
weight of a swallow)

Would that be an African or European swallow?