Juan Varela Simó is the protagonist of the 18th episode of Naturally. A biologist and great defender of the role of birds in our well-being, he was one of the main illustrators of Felix Rodríguez de la Fuente from 1976 until his death. Illustrator, cartoonist and writer, he has in the 'Guide to the Birds of Spain', one of his most outstanding publications, as it is the first publication of its kind written and illustrated by Spanish ornithologists and designed for amateurs, with nearly 70,000 copies sold and four editions. In this episode he talks about the importance of conserving the habitat of birds, their contribution to improving our mood and the role they play as indicators of the pollution suffered by cities, both at the acoustic and atmospheric level.