Spring: Iolo starts his journey during spring in Nant Ffrancon in the Ogwen Valley where he finds one of Britain’s most-threatened birds – the twite. Mountain guide Hannah Hughes takes him high up above the stunning glacial landscape of Cwm Idwal for a spectacular view of the high peaks. On the slopes of Snowdon, bluebells bloom, while shepherd Hefin Hughes keeps sheep off arctic plants. On the foothills of the Rhinog Mountains, cuckoos call. Iolo heads to a wonderful hidden river gorge in full flow and listens to the best dawn chorus in Snowdonia in an ancient woodland. He joins Josie Bridges, who is part of a team tracking pine martens that were released in mid-Wales during 2015 after apparently disappearing from the whole of Wales over 50 years ago. A family of pine martens has made its way to Snowdonia, a journey of around 50 miles from the release site. Iolo also discovers a relic of a past landscape. Bird Rock, an imposing crag in the Dysynni Valley, may have once overlooked the sea, and to this day cormorants still nest on the rock – it being Wales’s only inland nesting colony.