Rockhopper penguin reaching full growth, they are about 20 inches in height. Males and females cannot be distinguished just by looks, so a DNA test is conducted by taking a feather from the bird to determine its gender. Like many penguins, rockhopper penguins have a white belly and the rest of their body is black. Some characteristics that differentiate them from the other penguins are their red eyes, orange beak, pink webbed feet, and the yellow and black spiky feathers they have on their head. Although their yellow and black spiky feathers differentiate them from other penguins, rockhopper penguin chicks do not
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