Things have started to pick up today around the ponds from 1 Chiffchaff, now to 5 (4 collybita and 1 non calling presumed tristis). The presumed tristis responded well to tristis song playback - with wing quivering and being inquisitive the other collybita chiffchaffs ignored this recording. It was incredible how the presumed tristis morphed from a very buffy-grey bird in the shadows to subdued olive in the sunlight. It also showed yellow in the supercilium. Prior to the Dutch Birding article I would probably have put this bird down as an abietinus/tristis!  

Photos: presumed tristis top two and bottom left and collybita Chiffchaff bottom right;