Here is a nice article written for Vermont Ebird about Lincoln's Sparrows:
http://ebird.org/content/vt/news/little-brown-birds-of-confusion/

In my experience they are often, but not always in mixed species sparrow flocks, and rarely, if ever singing in the fall. 

Spencer Hardy, 
Middlebury



On Sep 18, 2013, at 5:42 PM, Martha Pfeiffer wrote:

> Does the Lincoln's sparrow mix with Fall Song Sparrows - or is it a solitary bird?  Is it singing in the Fall?
> Would appreciate any info anyone can give.
>  
>  Martha Pfeiffer
> Dorset