Jim, et. al.:

I haven't heard a grasshopper sparrow do this, they usually just sing their 
familiar song here.  Although grasshopper sparrows are not abundant here, I 
hear them all the time since a few breed around here (Jug Bay and Southern 
PG County).  By any chance could there have been chipping sparrows there 
also?  I ask because I've heard chippies make a "bubbly" song just as you 
described - I've heard it quite a lot from them (when I know it was a chipping 
sparrow).  I don't know what their bubbly song means, though I would like to 
know why they use it - if there is a reason.  The chippies do it here frequently 
enough, and since I hear grasshopper sparrows a lot but I have not heard 
them do the bubbly song (yet), I don't think grasshopper sparrows use it 
commonly here.  I wonder, was the grasshopper sparrow visible when you herd 
the bubbly song?  Usually when I hear the chippies do it, they seem excited 
about something (fussing over a grounded fledgling, perhaps?), but they are 
almost always OUT OF SIGHT when they make it.  Unlike their trill; although 
they aren't always visible while trilling, OFTEN they can be seen conspicuously 
perched when they trill.

Perhaps grasshopper, chipping, and other species of sparrows all make this 
bubbly song?  And do they all do it from out of sight?

Jeff Shenot
Croom MD