Multiple quail often gather under covering plants.  As a person creeps
toward the quail, the quail get alert, then nervous.  Finally one
quail cannot stand the situation any longer and flies away.  At this
point if the person freezes and makes no movements, the remaining
quail almost always fly away in  sequential order, not simultaneously.

I have many times seen 20-50 quail do this.

I am interested in the quail that remain after the first one flies
away.  Their situation is static, but they begin to fly away one by
one.  What is the signal that causes them to fly away one after the
other?

I suspect the signal is either the sound of another bird's wings
beating or the visual sight of another bird getting into the air. 
What research been done to answer this question?

Hi, thedoctor30215,

Thanks for the question -- it brings back many pleasant memories of
the times my Dad (who was an avid hunter) and I shared before I got
old enough to realize I liked being a girl better than my Dad's
'buddy.'. Until that point, he and I and my mighty BB rifle were out
in the woods almost every weekend. I'm quite familiar with the pattern
you've mentioned.

However, despite knowing that the quails' habit of flying off
individually, or sometimes in couples, is a covey preservation
mechanism, it was a bit tricky finding a cite-able source to back up
what my Dad taught me. I tried looking for such things as quail
habits, flight patterns of quail, quail characteristics in general,
etc. but came up empty. Them I realized I needed to look for an
association with hunting, since quail fly from predators.

I finally found a PDF website (requires Adobe Acrobat Reader to view)
which provides a good explanation of this flight pattern. The
information can be found on pages 15 and 16 of 99.

"Quail flush as a group for a reason, to prevent the predator (you) a
confusing whirlwind of targets. This reduces the predator's ability to
focus on one target, and increases the odds the predator will be
indecisive long enough to allow escape by all." The guide continues on
to describe how to adapt your shooting skills to this pattern.
GUIDE TO HUNTING QUAIL IN CALIFORNIA
http://www.dfg.ca.gov/coned/quailguide.pdf
HTML version:
://www.google.ca/search?q=cache:NYM2OWzoOAAJ:www.dfg.ca.gov/coned/quailguide.pdf+hunt+quail&hl=en&ie=UTF-8

This is a great website. Although its focus is on hunting these
fascinating birds, it provides such good information about the habits
and habitats (California focus) of the quail.

The Acrobat Reader is free software but, if you don't have it or don't
want it, you can view the site in HTML. (Images aren't provided in the
latter format, though.) I've provided you with both URLs.

I hope you find it as interesting as I. Again, thanks for the memories!

Best regards,
revbrenda
 

Search strategy:

hunt quail
://www.google.ca/search?q=hunt+quail&ie=UTF-8&oe=UTF-8&hl=en&btnG=Google+Search&meta=