Re: high altitude birds

["oryoki2000" oryoki2000]

"Greg Simmons" wrote:

> ...There is a large black bird that exists at those 
> altitudes in Tibet, possibly some sort of crow or raven...

Both Raven and Alpine Chough have been seen at 6200 meters, about the
elevation of Camp 1 on Everest.  Raven, in particular, is a species
with a wide set of vocalizations, even mimicing the sounds of machinery.

Birds have a more efficient way of passing air through their lungs
than mammals do.  This allows them to migrate at very high altitudes.
 Whooper Swans have been spotted on radar at 8800 meters.  

Corvids like the Raven and Chough are scavengers by nature. The birds
high on Everest were probably looking for a meal in the garbage and
dung cast off by climbing and trekking parties.

--oryoki