Re: Effect of extreme heat on birds

To: Birding-aus <>
Subject: Re: Effect of extreme heat on birds
From: Blair Wolf <>
Date: Tue, 3 Feb 2009 20:04:04 -0700
I thought I would just weigh in on the heat stress in the "chooks" (I
thinking that's a chicken in american english) as noted by wendy.  The
affect is a true temperature effect where the birds just can't lose enough
water evaporatively, and thus heat, to keep body temperatures below lethal
levels.  When the environmental temperature is above the animal's body
temperature (for birds this is usually a body temp (Tb) between 41 and 43C;
lethal Tb is between 46 and 47C), the animal can only lose the heat produced
by its metabolism and the heat it gains from the enviironment by evaporating
water.  Some strains of chooks are better at this that others and thus can
withstand higher environmental temperatures given enough drinking water to
stay hydrated.  Most birds evaporate the bulk of their water by panting,
although doves and pigeons can lose significant amounts through the skin. As
wendy noted, for evaporation to be most effective you want low atmospheric
humidities.  The strains of chooks that are having real heat stress problems
need to be in a cooler, dry environment and kept out of the sun.  if you
want the gory details, the following link will take you to a few papers that
have written on the topic as well as a paper I wrote on climate change and
small birds.  I appreciate all of the feedback and info you have been
sending on the heat wave.  I have a couple of pictures I can post that shows
several thousand dead budgies from a farmer western Australia if the list
wants to see them (they are 300kb each).



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