[mou] RFI - Call Help

[Pastor Al Schirmacher]

Had a call (song) this morning that I have not heard before (16 years of 
birding in the Midwest), will attempt to describe.

I was walking in the coniferous section of Blue Hill Trail, Sherburne NWR 
(near Princeton, MN) when a rolling song started about 100 yards to the east 
(much louder than the Chipping Sparrows and Red-breasted Nuthatches around 
me).  The song continued as the bird (apparently) flew overhead, stopped 
twice in the woods (again, apparently at the top of the 40+ foot coniferous 
trees), then proceeded west.

The song/call was loud (say, Hairy Woodpecker loud) - rolling - stayed on 
the same pitch for 3-5 seconds, then would go up or down a half step, 
calling again on a consistent pitch for another 3-5 seconds.  On most 
occasions (perhaps five minutes of listening), it would do a two pitch call, 
then cease - although on one occasion I counted four changes up or down 
(during flight).  The song was never slurred.  The space between notes was 
similar to a slower Swamp Sparrow's song, but the notes themselves were 
similar to - of all things - a Red Squirrel.

I received an impression of a medium-sized to larger bird, but never had a 
visual - and anyone who has listened to a Ruby-crowned Kinglet or Carolina 
Wren knows how deceptive loudness of calls versus size comparisons can be.

Any input (or questions) would be appreciated.

Al Schirmacher
Princeton, MN
Mille Lacs & Sherburne Counties