Much of Tunnicliffe's work depicted birds in their natural settings and other naturalistic scenes. He illustrated Henry Williamson's "Tarka the Otter". His work was also used to illustrate Brooke Bond tea cards and as a result was seen by millions of young people in the United Kingdom during the 1950s and 1960s. He also illustrated a number of books, including the Ladybird books. His work was characterised by its precision and accuracy, but also by the way in which he was able to portray birds as they were seen in nature rather than as stiff scientific studies.