Southern rockhopper penguin eye. The rockhopper penguin complex is confusing. Many taxonomists consider all three rockhopper penguin forms subspecies. Some split the northern subspecies ("moseleyi") from the southern forms ("chrysocome" and "filholi"). Still others consider all three distinct. The subspecies recognized for the southern rockhopper penguin complex are: The northern rockhopper penguin lives in a different water mass than the western and eastern rockhopper penguin, separated by the Subtropical Front, and they are genetically different. Therefore, northern birds are sometimes separated as "E. moseleyi". The rockhopper penguins are closely related to the macaroni penguin ("E. chrysolophus") and the royal penguin ("E. schlegeli"), which
Bird-of-paradise lek-type mating system. Others, such as the "Cicinnurus" and "Parotia" species, have highly ritualised mating dances. Males are polygamous in the sexually dimorphic species, but monogamous in at least some of the monomorphic species. Hybridisation is frequent in these birds, suggesting the polygamous species of bird of paradise are very closely related despite being in different genera. Many hybrids have been described as new species, and doubt remains regarding whether some forms, such as Rothschild's lobe-billed bird of paradise, are valid. Birds-of-paradise build their nests from soft materials, such as leaves, ferns, and vine tendrils, typically placed in a tree