Re: [SBB] Common Poorwill at Almaden Quicksilver

[Les Chibana <[[email protected]]>]

David,

If you are asking if they spend the winter in a state of torpor, Common 
Poorwill (COPO) don't appear to do so. They are capable of lowering 
their metabolism to a very low level (torpor) during times of low 
temperature. Hummingbirds do this as well. Birds can be in torpor 
overnight and maybe a bit longer. Hibernation often refers to spending 
the whole winter in torpor, as exhibited by high latitude bears during 
winter. But a secondary definition makes it about the same as torpor, 
with no indication of a long time period. The Birds of North America 
(BNA) account doesn't say that poorwill hibernate. In Kenn Kaufman's 
"Lives of North American Birds", he uses hibernation in quotes. In the 
Sibley Guide to Bird Life and Behavior, Robert Behrstock notes that 
there are reports of COPO going into extended periods of torpor through 
winter, but doesn't use "hibernate". In the John Terres Encyclopedia of 
North American birds, hibernation is used without quotes. The first 
three references are more recent than the last.

If there is another question/assumption here, i.e., does this mean that 
they are present year-round, the answer is, probably not. It depends on 
which reference you use. The BNA account shows our area a little 
outside their year-round range. The National Geographic Reference Atlas 
to the Birds of North America, edited by Mel Baughman, indicates that 
our area is at the edge of their year-round range. Their seasonal 
movement, or presence, is not very well understood. If there was a 
significant number (are there any?) of records of their presence in 
winter locally, we might more easily accept that they are present 
year-round and are just undetectable during winter in this area. Such 
is the case for many nocturnal, cryptically-marked species.

Les
---
Les Chibana
BirdNUTZ(tm) - Ornigasmic Birding
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On Jun 18, 2005, at 11:33 AM, David Forthoffer wrote:

> At 06:54 PM 6/17/2005, [[email protected]] wrote:
> > we also  saw two COMMON POORWILLS ...
>
> Those birds hibernate when it is very cold, right?
>
> David Forthoffer

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