[EBB Sightings] A third White-throated Sparrow in the yard??

Our small N. Berkeley yard has hosted a wintering White-throated 
Sparrow (and last year, two) for all but one of the last several years. 
This year, our first appeared on 27 Oct and a second this past Monday, 
19 Nov. Yesterday, we had an apparent THIRD. We did not see all three 
simultaneously, but we did have two white-striped birds together, as 
well as one of the white-striped birds in company with the tan-striped 
(maybe first-year) individual that has been present for a month.

The tan-striped bird is quite dingy, the tan supercilium appearing 
dusky and obscure immediately behind the yellow supraloral spot, and 
the white throat is strongly and fully partitioned by dark lateral 
stripes. I can't see confusing it with either of the other two birds.

To make all this seem a little less improbable, I wonder if these birds 
have a kind of specific affinity, attracting others of their kind to a 
reliable food source. Or maybe just staying together after moving south 
in small flocks from their breeding grounds. Notwithstanding the fact 
that they are usually reported as lone individuals around here.

Doug Vaughan
Berkeley