[TN-Bird] Torpor in birds
- From: "Charles P. Nicholson" <cpnichol@xxxxxxxxxxxxx>
- To: <raincrow@xxxxxxxxxxx>, "'TNbird'" <tn-bird@xxxxxxxxxxxxx>
- Date: Sun, 19 Jan 2003 13:37:30 -0500
On 1/19/03, Liz Singley wrote:
"James Brooks wondered if more bird species than
rubythroats and C wrens enter torpor because few birds venture out until the
day has warmed up a bit. I wonder if, instead, they are keen judges of the
temperature at which it becomes worth the energy expenditure required to
forage for food. I would be very interested to hear from our more hardcore
ornithologists on this subject."
The November 2002 issue of the Condor (the journal of the Cooper
Ornithological Society) contains the article "Avian Facultative Hypothermic
Responses: A Review" by McKechnie and Lovegrove. The ability to lower their
body temperature by a small amount for a short period of time (rest-phase
hypothermia) is widespread in birds. The ability for pronounced hypothermia
or torpor is much more restricted and known in the todies, the mousebirds,
hummingbirds, swifts, goatsuckers, and pigeons. To read the abstract of
this article, go to http://www.cooper.org/. Then, in the menu on the left
of the screen, click on "The Condor," then click on the November 2002 issue,
then click on the first article in the list of feature articles.
The ability to lower body temperature by 20 C or more is only known from the
hummingbirds, swifts, and goatsuckers. Very few passerines have the ability
to lower their body temperature more than 10 C, and no passerines approach
the ability of the non-passerine groups listed above. The only bird known
to truely hibernate is the Common Poorwill; the other species with
pronounced hypothermia apparently enter torpor on a shorter daily cycle.
Nothing is known, however, about the hypothermic responses in most avian
families.
Chuck N.
Norris, TN
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