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Hi Steve & All, July 27, 2015
I had forgotten what these feeders were like having seen them at a
distance recently but not examined them or used one for many years.
But lets get the Physics less mystical--
First "HB feeder outlets are" NOT "under hydrostatic pressure from the
height of sugar water inside the feeder". They will have a negative pressure
sufficient to balance this downward force. If that syrup were under
hydrostatic pressure at the business end then it would just run out. [This
is the same principle as used in a chicken watering station. It consists of
a pan about 2" high and about 3" larger in diameter than the reservoir. The
reservoir is a cylinder closed at one end and with several notches ~1/2'
deep cut in the wall at the open end. In use, the reservoir is filled, the
pan placed on it and the assembly is quickly inverted. After an initial
surge of water from the reservoir, sufficient to generate the required
negative pressure, further water can flow into the pan only after the level
in the pan is lowered below one of the notches.]
And tapping the feeder might well temporarily tilt it enough to increase
the effective diameter of the hole on the high side and let air in or
vibrate the unit enough so the drop 'stuck' on a lower side becomes unstuck
allowing air to enter on the high side. [Whenever measurements of pressure
are taken with a device which involves movement of a liquid meniscus in a
solid tube (thermometer, manometer) tapping is standard practice if the rate
of change in temperature/pressure is slow. So this does not really "inject a
bit of extra energy into the system". It just vibrates that gas/liquid/solid
point of contact enough to reach a point less far from true equilibrium.
It is a good thing the birds understand all this or they would go
hungry/thirsty.
Yt, DW Kentville
----- Original Message -----
From: "Stephen Shaw" <srshaw@Dal.Ca>
To: <naturens@chebucto.ns.ca>
Sent: Monday, July 27, 2015 1:00 PM
Subject: Re: [NatureNS] how does Downy WP gather HB food
> Possibly both but maybe neither, perhaps just using a more natural
> aptitude.
> HB feeder outlets are under hydrostatic pressure from the height of sugar
> water inside the feeder, and what stops this coming out of the ‘flower'
> holes and letting air bubbles in is presumably surface tension at the
> hole. If you inject a bit of extra energy into the system by accidentally
> tapping the feeder, an air bubble easily goes in and a drop comes out, at
> least it does on our two small feeders. One thing that woodpeckers are
> good at is intentionally tapping things quite hard, so that might be all
> it takes to get drops to pop out of the hole in the ‘flower’ for
> consumption.
>
> One of your downys may have learned to do this. An interesting question
> then is whether the WP has shown this to its offspring who then learned
> the trick. This goes back to the situation that started on the south of
> England in the 1940s or perhaps earlier, where blue tits (chickadee-like
> birds) learned to peck holes in the aluminum caps of milk bottles
> delivered routinely in the early morning by a ‘milkman' to the outside of
> each house, well before the advent of supermarket milk. This allowed the
> birds to sip the cream off the non-homo milk (it was countered by leaving
> an inverted empty baked bean can for a cooperative milkman, who placed it
> over the milk bottle to protect the cap). The interesting thing is that
> this practice by the birds spread north slowly year by year as a learned
> behaviour to encompass most or maybe all of the UK, transmitted socially
> from bird to bird. For this to have spread, the human countermeasures
> must have experienced a serious response lag, showing that birds are
> smarter than humans. Maybe there are other examples but this is the best
> known.
> Steve (Hfx)
>
> On Jul 26, 2015, at 5:59 PM, nancy dowd <nancypdowd@gmail.com> wrote:
>
>> A Downy Woodpecker visits my Hummingbird feeder many times each day. It
>> obviously gets some of the sugar water by either lapping up spillover
>> and/or inserting its tongue in the hole. I cannot tell which method it is
>> using:
>> https://www.flickr.com/photos/92981528@N08/19845924340/in/dateposted-public/
>>
>> After working awhile at the "flower", it tilts its head back seeming to
>> chug at the liquid for ~10s:
>> https://www.flickr.com/photos/92981528@N08/19845925830/in/dateposted-public/
>>
>> Anyone know if the Downy's tongue is actually small enough to gather the
>> sugar water directly through the hole? Or is it being more of a cleanup
>> crew and just squeegeeing up seep on the surface? Fun to watch in any
>> case. (Excuse the photo quality- they were taken through a dirty window
>> with an iPhone.)
>>
>> Nancy
>
>
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