Rockhopper penguin have them; these feathers develop with age. Their orange beak is initially black, but as the penguins get older, their beaks turn orange. Due to the harsh rocky environment, they cannot slide on their bellies like most penguins, so they hop to get from one place to another. What separates rockhopper penguins into subspecies is their location of reproduction and reproductive behaviors. The difference in mating signals found between the subspecies "E. chrysocome" (southern) and "E. moseleyi" (northern) seems to have occurred quickly, thus these behavioral changes are enough to isolate these taxa. Southern Rockhopper penguins are split into two
What Bird is That? all-time best seller in Australian natural history and is still in print today. While sales and stature of Cayley’s original collection continued to grow, the prolific artist and ornothologist Cayley was working on a much more ambitious project – his so-called “big bird book”. From about 1918, he was creating illustrations of subspecies, plumage stages and eggs (now lost) of all known Australian birds. The project was incomplete at the time of his death in 1950, although the illustrations were all but finished. The ornithologist Terence Lindsey revived Cayley’s plans in the 1980s, creating the last and most significant revision