[wisb] Re: Bird Feet RFI
- From: Erik Bruhnke <birdfedr@xxxxxxxxx>
- To: bgsloan2@xxxxxxxxx
- Date: Wed, 9 Feb 2011 13:18:15 -0600
Sorry about the confusion with my post earlier. I forgot to elaborate on the
picture in the link I included, to tie it in with my description... The
upper portion of the leg has a more constant temp (as the blood goes back
into the bird. Both Doug and Bernie are correct too. When I said "from upper
leg to foot," I did not mean to include the actual foot of the bird, which
as Bernie mentioned from the article that William posted, the feet can be
just slightly above freezing. This is most pronounced/noted in birds that
spend a significant time around water, as the likelyhood of freezing their
feet becomes greater around all of the freezing water.... ducks and gulls.
Good birdwatching everyone,
Erik Bruhnke
Duluth, MN
NATURALLY AVIAN - Bird photography and guided birdwatching tours
www.pbase.com/birdfedr
www.naturallyavian.blogspot.com
birdfedr@xxxxxxxxx
On Wed, Feb 9, 2011 at 10:40 AM, B.G. Sloan <bgsloan2@xxxxxxxxx> wrote:
> 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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