As far as I'm aware there have been three records of Booted in Japan and all in the Sept/Oct migration period. Two of those records were on Hegurajima so finding one here clearly outside the migration window means either it isn't Booted and I've just made an awful fool of myself or it could have arrived earlier and have been in the area for some time.
So is it a Booted or not?
Rather phyllosc-like first glance, my first two thoughts were tristis but not with pink legs surely and Dusky but it's a bit too milky-tea and where the eyestripe and supercillium.
The tail is actually quite square and not at all accro-like. The upperparts are concolourous from crown to uppertail coverts. Only the primaries. tertial centres and tail are blackish-brown, though all have distinct pale fringes.
Throat and upper breast (and undertail coverts) white, flanks slightly warmer. Eyestripe almost non-existent at most angles, the supercillium was usually obvios behind the eye but not in this shot. Upper mandible dark with pale cutting edge, lower mandible pale with restricted dark tip.
At some angles it has a slightly darker border to the supercillium before the eye. The legs are pinkish and the feet greyer.
It must have been in a stand of old withered maize that was being cut (and attracting fantastic numbers of birds. I heard a rattle at one point, long before I saw the bird, that reminded me vaguely of a ficedula, not quite but enough to make me wonder what it was. Then when I finally did see it, it gave a series of rather soft ticks. It tail-wagged once.
If it has been in the maize it will be forced to move but while I was there it was in the grass at the road edge and on the remains newly cut maize. It disappeared for some time and I drove 50 metres to the end of the field and it suddenly flew in from the opposite direction and perched on the tallest stalks for a moment but then flew across the field and into reeds along a broad drainage channel.
Whether this mobility was due to its favoured habitat just having been cut or whether it always covers a large area I can say. But the former seems likely.
If it has been around for some time it may be twitchable but it may equally be difficult to relocate if it gets into the endless drainage channel vegetation.
So there it is. Booted is the only thing I can imagine it can be. Sykes's might be the only other possibility but I think not.
Anyway, a quick post to let people make up there minds about it.