Siberian Chiffchaff

This afternoon I checked the back path north of South Farm Road looking for Chiffchaffs. I was pleased to find at least one, probably two Siberian Chiffchaffs feeding in the wet ditches with an obvious Common Chiffchaff. Chiffchaffs are so variable in plumage and such features change so much dependent on the light. I am generally quite cautious unless a bird calls.

Siberian Chiffchaff - Calling a single mournful "peep" note.
Warm brown ear coverts, strikingly white underparts, dark bill and green mostly confined to wing and tail feathers

Common Chiffchaff - Not the bird seen today, but a good comparison

Probable Siberian Chiffchaff - Not heard to call, but still fairly striking with bright white underparts.
Possibly too green on mantle but nowhere near as striking green as Collybita