The Ornithology of Australia comprises three volumes (of an uncompleted set) of lithographed, hand-coloured, illustrations of Australian birds with accompanying text.

[2] In 1877 Diggles produced what was essentially a two-volume second edition of the previously published work, using 123 of the same plates and renamed Companion to Gould's Handbook, or, Synopsis of the birds of Australia, containing nearly one-third of the whole, or about 220 examples, for the most part from the original drawings, though the spine title was simply Diggles' Ornithology.

[1] The title referred to John Gould's 1865 book Handbook to the Birds of Australia.

Diggles lacked the funds to continue publishing the series of lithographs.

His manuscript and original plates, including those unpublished, were later acquired from Diggles’ son by publishing firm Angus & Robertson which presented them to the Mitchell Library in Sydney.