The other day Gary Reynolds sent me a photo he'd taken at Cilgerran of one of the above asking if I had any views on its id. The picture was great but alas without any sound my own field skills were too limited to help. An article in British Birds magazine in 2014 states; numerous identification criteria have been proposed in the past 50 years, based primarily on information gained of birds in the hand, although none are judged to be wholly reliable. The best separation feature for birds in the field is considered to be voice, yet the vocal repertoires of both species have not been fully documented.
This morning I went for a wander along Nant Brynmaen near Stag's Head. Arriving at a ribbon of mature woodland (marked on 1:25000 map) I came across a pair of the above. But which? They were calling very loudly at close range but I just did not recognise the call. Lack of pale panel in the wing suggested Marsh but it was not until after about 5 minutes that they changed their tune, frequently repeating the distinctive "pitchuu" call (Marsh Tit). Immediately upstream of here, stretching for a kilometre or so, are numerous fields, marked on the map as bracken, heath and rough grassland, but now rapidly reverting to willow/birch scrub. Five singing Willow Tits responded to the RSPB playback device that I was using. However, my views of each were far from perfect and without the magic machine I would have struggled to locate and identify any of these birds I think.