I am writing this from my phone, so apologies for any mistakes.
I had this email drop in my inbox this afternoon. I must stress I do not know the observer, so have no idea how reliable this is. Naturally I have asked for more info...
"We were recently visiting Dartmoor, 2nd June 2011, and had climbed the lower slopes of Widgery Tor (Brat Tor on the map) when we spotted the Blue Rock Thrush, no photo I'm afraid, but since being home have researched the bird and can positively say that it was the Blue Rock Thrush. Have there been any other sightings on Dartmoor. If you need any further info please get in touch, I would be keen to know whether this bird is now coming over to England."
I thought I'd post this in case anyone was passing the area...
