[EBB Sightings] Mines Road Poorwill

Folks:

This morning, 10/21/09, I was driving Mines Road at dawn and spotted 
a COMMON POORWILL flying above the road at M.P. 11.02 about 0641 hr.

Aside: Common Poorwills are particularly fascinating as their 
populations have two approaches to winter cold and reduced food 
resources.  Northern birds migrate south, whereas southern birds 
enter holes (presumably ground squirrel holes) and reduce their body 
temperature and food requirements.  Physiologists have studied the 
species and suggest that they can last 120 days doing this.  That's 
not enough time for northern birds, but it is fine for southern birds 
(who sometimes awake and forage during warm periods).  What are the 
boundaries?  Big unknown.  I think Don Roberson has suggested that 
most birds in Monterey County do not migrate.  What proportion 
migrate and what proportion hibernate is unclear in central 
California.  I would think that bayside birds might have less cold to 
deal with whereas those in the Diablo Range might have to 
migrate.  I'm not sure whether observer records, even over many 
years, will shed enlightenment on this, but maybe they will.  In 
Santa Clara County we do know that northern birds migrate in October 
as we both see them and band them on the valley floor, a place where 
they are absent during the breeding season.

Bill Bousman
Menlo Park