Rockhopper penguin is one of the world’s most numerous penguin populations, it is estimated that the population declined by some 30 percent over the final 30 years of the 20th century. The cause of this decline is mainly unknown, but scientists have speculated that humans are involved, mostly by commercial overfishing, oil exploitation, and pollution. Recent research has shown that rockhopper penguin population declines with changes in ocean surface temperature, indicating a direct impact from climate change. These activities have depleted much of the rockhopper penguin’s food supply and raised the sea surface temperatures, and because this species is geographically isolated to
What Bird is That? of "What Bird is That?" It was published in 1984 and incorporated all of Cayley’s paintings created over many years for his vision of releasing a “big bird book” and included a revised taxonomy. In the 53 years since its first edition, more than a hundred new bird species had been identified in Australia. Scientific names had been changed and groups of birds had been reordered. Lindsey brought "What Bird is That?" up-to-date with the latest birding conventions of the time, as well as contributing a valuable supplementary list of birds and a scholarly catalogue of Cayley’s paintings. The "Signature