Since Nashvilles of all ages/sexes have yellow undertail coverts, there is one other possibility for the ID of the bird you saw with an eye ring and white undertail coverts, namely an imm. F Magnolia. See Sibley, p. 485.
The key question is: did the bird have wing bars (Magnolia) or not (Nashville)?
From: Fred and Chris Pratt <[log in to unmask]>
To: VTBIRD <[log in to unmask]>
Sent: Fri, Sep 18, 2015 8:14 pm
Subject: Re: [VTBIRD] Nashville Warbler question
I think your call was correct - probably a fall female or immature.
----- Original Message -----
From: "Martha Pfeiffer"
<[log in to unmask]>
To: "VTBIRD" <[log in to unmask]>
September 18, 2015 4:43:08 PM
Subject: [VTBIRD] Nashville Warbler question
smattering of warblers at Emerald Lake State Park in East Dorset today were
feeding in the berry bushes west of the parking lot. I identified one as a
Nashville Warbler. I had close up views of it's white undertail/belly.
However, Sibley's and two other references show bright yellow from breast to
undertail. Perhaps the fall Nashville or first year bird has the white? Other
markings were the grey head, white eye ring and bright yellow breast.Comments
are welcome! Martha Pfeiffer , Dorset