Northern rockhopper penguin the ship broke up, leaving an oil slick that surrounded the island, threatening its population of rockhopper penguins. Nightingale Island has no fresh water, so the penguins were transported to Tristan da Cunha for cleaning. Northern rockhopper penguin Recent studies show the northern rockhopper penguin, Moseley's rockhopper penguin, or Moseley's penguin ("Eudyptes moseleyi") distinct from the southern rockhopper penguin. A study published in 2009 showed that the population of the northern rockhopper had declined by 90% since the 1950s. For this reason, the northern rockhopper penguin is classified as endangered. The rockhopper penguins have been considered to consist of two
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