Quite early in his career, Turner became interested in natural history and set out to produce reliable lists of English plants and animals, which he published as "Libellus de re herbaria" in 1538. In 1544, Turner published "" ("The Principal Birds of Aristotle and Pliny..."), which not only discussed the principal birds and bird names mentioned by Aristotle and Pliny the Elder but also added accurate descriptions and life histories of birds from his own extensive ornithological knowledge. This is the first "printed" book devoted entirely to birds.