Rockhopper penguin subspecies and they are defined by their location of reproduction. The subspecies "E. c. filholi" (eastern) is known to reproduce in the sub-Antarctic around the Prince Edward Islands, Crozet Islands, Kerguelen Islands, Heard Island, Macquarie Island and Campbell, Auckland and Antipodes Islands. The subspecies "E. c. chrysocome", which may be referred to the true southern subspecies, reproduces at offshore islands in southern Chile, Argentina and at the Falkland Islands. The Falkland Islands are known to have one of the largest populations of Southern Rockhopper penguins. The subspecies in the group are: Northern rockhopper penguins breed in cool temperate climates including
What Bird is That? according to their usual habitat. The accompanying text included brief notes on distribution, breeding and behaviour. While initial sales were poor, history tells us that Cayley had accurately discerned a market need and successfully responded to it. During WWII sales accelerated and Cayley’s first collection, reprinted time and time again, eventually became a household name among birdwatchers and the book was recognised as an Australian classic. The original sponsorship of "What Bird is That?" proved a great investment for the Gould League, who benefited from the sale of its numerous reprints and revised editions. By 1960, it was rated the