Iolo Williams exploring Pembrokeshire’s less well-known wildlife spots away from the well-trodden tourist paths. Iolo searches the lower slopes of the Preseli Mountains and finds newly arrived migrant birds, including one which nests under rocks. He also hunts for the mesmerizing lights produced by glow worms near Martin's Haven. And he experiences a real treat , watching an iconic nocturnal bird, the barn owl, hunt over rough grassland at dusk.