The League published a large number of his paintings and his birds were reproduced on more than two million membership cards. Cayley truly believed in the value of ornithology and in memory of his father, he created a scholarship in Economic Ornithology at Sydney University, to be administered by the League and funded by royalties from What Bird is That? The scholarship was eventually extended to post-graduate students involved in wildlife study or management relating to birds from universities around Australia.
As well as an author and artist, Cayley was a prominent ornithologist. A Fellow of the Royal Zoological Society of New South Wales, he was elected President in 1932–1933. He was also President of the Royal Australasian Ornithologist's Union in 1936–1937.