Iolo Williams explores the wildlife of Anglesey. Wales's largest island is renowned for its coastal beauty, but it also has fantastic marshland and heathland with spectacular wildlife. Iolo watches breeding marsh harriers - majestic birds of prey that have only recently started to nest in Wales. He finds stoats, grey seals and lizards. He also visits Puffin Island to find the only breeding site in Wales for eider ducks. On a disused railway line, he finds breeding adders.