Southern rockhopper penguin may just be a colour morph of the macaroni penguin. Interbreeding with the macaroni penguin has been reported at Heard and Marion Islands, with three hybrids recorded there by a 1987-88 Australian National Antarctic Research Expedition. The southern rockhopper penguin group has a global population of roughly 1 million pairs. About two-thirds of the global population belongs to "E. c. chrysocome" which breeds on the Falkland Islands and on islands off Argentina and southern Chile. These include most significantly Isla de los Estados, the Ildefonso Islands, the Diego Ramírez Islands and Isla Noir. "E. c. filholi" breeds on the Prince
What Bird is That? kookaburra seated on and within a large red question mark. It contains 36 coloured plates of paintings of Australian birds by the author, as well as several black-and-white photographic plates of habitat. There were numerous reprints and revised editions in various formats produced well into the 1980s. The first edition was sponsored by the Gould League of Bird Lovers of New South Wales of which Cayley was a Council member. In return for its sponsorship, Cayley offered the Gould League four tenths of his 10% book royalty. However, initial sales were slow and in 1935 he sold his entire share