This morning I heard it in front of the Bascom House then got on it a short while later out in the open on a path in the Wildflower Garden where it sang constantly.   The path was near the beginning of the Garden and on the side closest to the field.  I used my birdpod to id the strange song.  I could tell it's small size because it was standing next to a song sparrow for part of the time.   There were song, lincoln, chipping, white-throated and field sparrows all over.  Very few warblers in the Wildflower Garden and immediate area.  
Debbie Trowbridge
St. Louis
The Audubon Society of Missouri's Wild Bird Discussion Forum
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