Flava palava

I had another check of the horse paddocks just south of Cotham Flash on the way home from work tonight. This produced 5 Northern Wheatears, and a nice flock of 11 Yellow Wagtails, a species I never get bored of. Among them was a stand-out bird with a bluish-grey and olivey head (with tones changing with different angles and light conditions), a whitish throat and supercilium, and a yellow belly becoming more washed out across the breast. I struggled to digiscope it as it wouldn't stand still, and the two horses that live in the paddock kept standing in front of me...

I did some googling when I got home, and came across some images on the Birding Frontier website of a possible first-summer male Blue-headed Wag, which this bird looks rather like (to my eye), and interestingly, two of the features referred to appear to be present: (i) the outermost 2 (or 3?) greater coverts appear to be a different generation from the others, being shorter, with fine whitish fringes, whilst the other GCs have broader, more olivey and less well defined fringes, and (ii) the wings look a bit brown, not fresh black. An interesting bird.