Subject: Re: thermoregulation
Date: May 5 09:16:54 1995
From: Peter Rauch - peterr at violet.berkeley.edu


>Date: Thu, 04 May 95 18:52:46 PST
>From: Jack_Bowling at mindlink.bc.ca (Jack Bowling)

>True. This is because the *rate of temperature change* between the
>organism and its surroundings is *directly* proportional to the
>conductivity of the fluid. Thus an equilibrium temperature is reached much
>more quickly in water than air. Which of course makes it all the more
>interesting how waterbirds manage to survive so well.

Interesting, but not necessarily puzzling. Actually, the conductivity is
between the water and _some part of the organism_. So, for example, if
it is between the feathers and the water, there's not much heat from/in
the feathers to lose to the water. For thick, scaly legs, perhaps there
is little heat conducted _within_ the bird between the internal tissues
of the leg and the outer scaly portion, and thus little heat to lose to
the water (if the scaly portion can act as an insulator). Or, as some have
mentioned, there may be active pumping/shivering/high metabolic
activity on the part of the bird to counteract heat losses. Or maybe
they're warm, and sticking the legs in the water is the only way to
moderate that heat load.

And, depending on how much the water is circulating around the legs, there
might be less transport of heat away from the legs than one would be led
to believe from average water temperature readings in the neighborhood of
the bird.

Or, all those things....
Peter