ajohn

On what basis do you consider the Leaf Warbler to be claudiae? Why not fokiensis?
My understanding was that no reliable criteria had been found to separate non-singing individuals, so it would be interesting to know what to look for.

ajohn

OK, I understand that. There's also, of course, 'Pintail/Swinhoe's', and now 'Arctic/Japanese/Kamchatka'.
I wonder whether some of these may actually be separable on features that have not yet been recognised.