Many thanks to all those who have responded (Tim Spahr, Albert Goetz, Kari,
Gerry Hawkins, John Dennehy, Robert Ostrowski, Chris Starling, Vanessa
Girton, Jeff Shenot, Elise Kreiss, Jim Wilson, did I miss anyone?).

I'm not certain that we really have a concensus.  The nominees are Northern
Parula, Blackburnian Warbler, Cerulean Warbler.  A few individuals based
their opinions on the longer (about 1:41 mins long) audio clip:

http://www.cs.umd.edu/~farrell/UNK_5May08_LONG.wma

The count is:
Blackburnian 5
Parula 2
Cerulean 3

While that seems to lean in favor or Blackburnian, I'd like to throw in some
comments which don't support that ID:

"Blackburnian never ends in that terminal note like that, and it is never as
strong and emphatic.  It is more thin and wiry.  The Cerulean sings two
songs.  But the
key, defining characteristic is that terminal buzz.  There's no other
warbler that does it."

"I don't like Blackburnian for two reasons.  The end note here is a buzzy
note; with Blackburnian it is a clearer whistle that is higher than that of
your bird."


If it helps to listen again to the longer version, please do... I'd love to
get additional ideas, given both the tally and the above comments.  After
listening to recordings of these 3 species, I'm leaning toward cerulean, but
I know that most of you have much more experience than I do.


Thanks again to all who replied to my first email and thanks in advance to
those contributing additional input,
Ryan