I was just listening to that on my Petererson series "Birding by Ear" CD 
and the Junco's song is desccribed as being a "bell-like" trill vs. the 
Chipping Sparrow's which is a drier sound.  I would highly recommend this 
CD.  Also the Cornel Lab of Ornithology's Macaulay Library has a great web 
site where you can search for and listen to bird calls.  Here it is:

Ann Lewis
Morrisville, VT

----- Original Message ----- 
From: "jane" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, April 01, 2007 5:30 PM
Subject: [VTBIRD] Trills

> Does anybody have any good tips for distinguishing the trill of a Chipping 
> sparrow from a Junco?  My chippies are due back any day now but I've still 
> got lots of Juncos around, and I can't tell whether the trilling I'm 
> hearing is one or the other!
> Jane
> Shoreham