[wisb] Re: Bird Feet RFI
- From: "B.G. Sloan" <bgsloan2@xxxxxxxxx>
- To: wisbirdn <wisbirdn@xxxxxxxxxxxxx>
- Date: Wed, 9 Feb 2011 08:40:13 -0800 (PST)
Erik Bruhne said:
"By doing so, the blood remains warmer throughout the leg longer, and it
creates a more average blood temperature from upper leg to foot... whereas with
people, it's all warm, eventually turning all cold because of the lack of
heat-sharing."
Maybe I'm just misreading it, but William Mueller just posted a link to an
article that sort of seems to say the opposite:
"In addition, by constricting the blood vessels in its feet a bird may further
decrease heat loss by reducing the amount of blood flow to its feet at low
temperatures. Thus while the core temperature of a duck or gull standing on ice
may be 104 degrees F, its feet may be only slightly above freezing."
Bernie Sloan
Milwaukee
--- On Wed, 2/9/11, Erik Bruhnke <birdfedr@xxxxxxxxx> wrote:
> From: Erik Bruhnke <birdfedr@xxxxxxxxx>
> Subject: [wisb] Re: Bird Feet RFI
> To: manderson@xxxxxxx
> Cc: "wisbirdn@xxxxxxxxxxxxx" <wisbirdn@xxxxxxxxxxxxx>
> Date: Wednesday, February 9, 2011, 9:56 AM
> Marge,
> I meant to send this earlier, but didn't get around to it.
> Scott is totally
> correct. The term that I learned when I took ornithology a
> few years ago was
> "countercurrent exchange," which is basically having the
> temperature of the
> blood stay relatively constant as the blood moves through
> most of the leg.
> Here is the thing... in people, the blood in our
> extremities flows to the
> tips/outermost portions of the extremities (via arteries),
> then flows back
> to our core (via veins). Birds have this ability to
> transfer warmth from the
> arteries (as the blood moves throughout the leg) to the
> veins in the leg
> (the returning portion of blood). By doing so, the blood
> remains warmer
> throughout the leg longer, and it creates a more average
> blood temperature
> from upper leg to foot... whereas with people, it's all
> warm, eventually
> turning all cold because of the lack of heat-sharing. Here
> is a diagram I
> found online. Think of the two orange columns as arteries
> (left) and veins
> (right), with the numbers describing the transfer of heat.
>
> http://www.knowledgerush.com/wiki_image/c/c2/Countercurrent_exchange.png
>
>
> Hope this makes sense. Good birdwatching,
> Erik Bruhnke
> Duluth, MN
>
> NATURALLY AVIAN - Bird photography and guided birdwatching
> tours
> www.pbase.com/birdfedr
> www.naturallyavian.blogspot.com
> birdfedr@xxxxxxxxx
>
> On Tue, Feb 8, 2011 at 3:11 PM, Marge Anderson <manderson@xxxxxxx>
> wrote:
>
> > Hello WisBirders:
> > I read somewhere that there is something about bird
> legs/feet that makes
> > them able to tolerate the cold with their feet
> exposed. Now I can't
> > remember what it was or where I read it. This
> topic came up in our office
> > kitchen between me and a colleague who is raising
> urban chickens. I said I
> > thought there would be many WisBirdnetters who would
> know the answer to
> > this, and since our email traffic is low in this
> pre-migration period, it
> > was a good time to toss it out there.
> >
> > Marge Anderson
> > Dane (and Vilas) County
> >
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