After only succeeding with hearing the Yellow browed warbler at
Kenfig yesterday, I decided to walk the east pool shore and head
back to the car park via the path from the north pool up to the main
road. There is a stand of Wych elm near the top of the path just
behind the bus shelter and a search for leaf mines produced this
one, which pretty much matches the photos on UKmoths and the
descriptions in the guides.