Southern rockhopper penguin may just be a colour morph of the macaroni penguin. Interbreeding with the macaroni penguin has been reported at Heard and Marion Islands, with three hybrids recorded there by a 1987-88 Australian National Antarctic Research Expedition. The southern rockhopper penguin group has a global population of roughly 1 million pairs. About two-thirds of the global population belongs to "E. c. chrysocome" which breeds on the Falkland Islands and on islands off Argentina and southern Chile. These include most significantly Isla de los Estados, the Ildefonso Islands, the Diego Ramírez Islands and Isla Noir. "E. c. filholi" breeds on the Prince
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