Probably not flavissima

Yesterday's ringing in the reedbed was dismal due to high winds and an apparent general lack of birds, although we did manage to catch another Wood Sandpiper in the walk-in cage trap. Today was much better with close to 120 birds ringed, mostly "lighthouse garden species" such as Willow Warbler, Lesser Whitethroat, Spotted Flycatcher, and Common Redstart, including this lovely adult male:


We've been catching a few Yellow Wagtails most mornings. We should be catching flava and thunbergi (probably more of the former, from what I've seen) but variation is striking. In the past couple of days, we've caught two birds with strongly saturated yellow supercillia/malar and rather contrastingly dark ear coverts. I've seen a few birds like this claimed as vagrant flavissima before and indeed they're rather eye-catching; but I'm not convinced that's what they are since a) they're roosting in the reedbed in Falsterbo in autumn (should we really expect 2/25 of the birds we catch to be vagrant flavissima?) and b) they don't really look like flavissima... That said, I have no idea what they actually are. Variation in flava/thunbergi seems the obvious if not terribly satisfying answer.

Bird 1 (adult):

Bird 2 (first-year):