[NatureNS] hummingbird feeder question

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From: Sherman Williams <shermw@xcountry.tv>
Date: Thu, 29 May 2008 02:09:38 -0300
To: naturens@chebucto.ns.ca
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AIR PRESSURE outside the feeder EQUALIZES  with the forces inside .

I think the main principle that makes the hummingbird (inverted  
bottle) work successfully (most of the time) is due mainly to subtle  
differences in air pressure equalizing. Air pressure outside exerts a  
force  and there are the forces inside the bottle.  Filling the  
bottle and inverting it abruptly,  creates a partial "vacuum", as  
just enough fluid escapes from the bottle for the forces to equalize.  
In this state of equilibrium, the fluid remains nicely inside the  
bottle. It remains that way until something disturbs the delicate  
balance.

If enough  fluid inside is removed (as the hummingbird "sips"), the  
balance is broken, air outside is able to push its way inside  
(bubbles) until the equilibrium of forces is restored.   Warming the  
air inside (causing the air to expand)   or   if air can leak in from  
other than at the bottom,  the equilibrium is broken from within, and  
the feeder fluid drips out.

There must also be a relationship between the container size/shape  
and the opening at the bottom, etc., that if exceeded will not allow  
that neat balance to exist.    I grew up on a poultry farm and a  
common watering dish for the young chickens was a one gallon,  
galvanized container, about 9 or 10 inches in diameter at the open  
end, and tapered to about 5 inches diameter at the closed end.  It  
was filled to the top while upright, a pan (about a foot in diameter) 
put over the large open end, then the two were abruptly inverted and  
set on the chicken pen floor. A small tapered wedge like a half  
clothes pin was inserted between the pan and the container.   There  
would be a brief "glug, glug" until the system equalized. A shallow  
depth of water would appear all around in the pan and then stop, just  
enough water  in the bottom of th pan that the chicks could drink.    
After several chicks drank,   you would hear a "glug" as a bubble of  
air entered the container near the wedge. The water was slowly  
dispensed in this way until the chicks emptied the containers.  I  
spent a few hours of my youth doing refills. But I must say the  
method worked very well. As some kids would say today,  "Sweet idea."

My take on an answer to the question...........Cheers, Sherman


On 28/05/2008, at 7:15 PM, Andy Moir/Chris Callaghan wrote:

> We put out a couple more hummingbird feeders today, and I could not  
> come up with a good explanation as to why the water just doesn't  
> drain out.  I'm sure you all know the type of feeder I'm talking  
> about.  A plastic container you fill with liquid, then you screw on  
> a red plastic part that has four perches and a flower like design.   
> You turn the whole thing upside down and hang it.  So why doesn't  
> the liquid just drain out?  Why does it come out for the  
> hummingbirds, but not for gravity?
> Pondering the truly great question of our time in Freeport, I look  
> forward to an answer.
> Andy


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<html><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; ">AIR PRESSURE outside the feeder =
EQUALIZES =A0with the forces inside .<div><br =
class=3D"webkit-block-placeholder"></div><div>I think the main principle =
that makes the hummingbird (inverted bottle) work successfully (most of =
the time) is due=A0mainly to subtle differences in air pressure =
equalizing. Air pressure outside exerts a force =A0and there are the =
forces inside the bottle. =A0Filling the bottle and inverting it =
abruptly, =A0creates a partial=A0"vacuum", as just enough fluid escapes =
from the bottle for the forces to equalize. In this state of =
equilibrium, the fluid remains nicely inside the bottle. It remains that =
way until something disturbs the delicate balance.=A0</div><div><div><br =
class=3D"webkit-block-placeholder"></div><div>If enough =A0fluid inside =
is removed (as the hummingbird "sips"), the balance is broken, air =
outside is able to push its way inside (bubbles) until the equilibrium =
of forces is restored. =A0 Warming the air inside (causing the air to =
expand) =A0 or =A0 if air can leak in from other than at the bottom, =
=A0the=A0equilibrium=A0is broken from within, and the feeder fluid drips =
out. =A0</div><div><br class=3D"webkit-block-placeholder"></div><div>There=
 must also be a relationship between the container size/shape and the =
opening at the bottom, etc., that if exceeded will not allow that neat =
balance to exist. =A0 =A0I grew up on a poultry farm and a common =
watering dish for the young chickens was a one gallon, galvanized =
container, about 9 or 10 inches in diameter at the open end, and tapered =
to about 5 inches diameter at the closed end. =A0It was filled to the =
top while upright, a pan (about a foot in diameter)put over the large =
open end, then the two were abruptly inverted and set on the chicken pen =
floor. A small tapered wedge like a half clothes pin was inserted =
between the pan and the container. =A0 There would be a brief "glug, =
glug" until the system equalized. A shallow depth of water would appear =
all around in the pan and then stop, just enough water =A0in the bottom =
of th pan that the chicks could drink. =A0 After several chicks drank, =A0=
 you would hear a "glug" as a bubble of air entered the container near =
the wedge. The water was slowly dispensed in this way until the chicks =
emptied the containers. =A0I spent a few hours of my youth doing =
refills. But I must say the method worked very well. As some kids would =
say today, =A0"Sweet idea."</div><div><br =
class=3D"webkit-block-placeholder"></div><div>My take on an answer to =
the question...........Cheers, Sherman</div><div><br> <span =
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