Yesterday I think I had either a Lincoln's sparrow or Swamp Sparrow at the
end of my yard, near blackberry brambles and a wet(landish) area behind it.
 I have never seen a Swamp Sparrow to my knowledge, and I've only gotten
fleeting glimpses of Lincoln's sparrows which were pointed out to me on
bird walks.  The things that stood out through my binoculars were a
distinct Buffy/tan Malar stripe, light gray belly, not sure whether there
were stripes on the chest or not.  It seemed a bit nervous once it saw me,
and kept its crown and tail raised. I am not sure whether the crown was
rusty or not! I had seen a similar bird behind my house in some brush under
an old broken apple tree, and also thought of LIncoln's because of its
quick sort of nervous manner.. I'm used to everything turning out
eventually to be a song sparrow, but these birds seemed shorter in length
and a little smaller.  Is there anything in my description that would be
telling one way or the other? (raised crown and tail?)