Northern rockhopper penguin two genera, "Austrogoniodes" and the monotypic "Nesiotinus". Within rockhopper penguins, the host-specific louse "Austrogoniodes keleri" is present only on southern rockhoppers; the multi-host "Austrogoniodes concii" parasitises only northern rockhoppers and "Austrogoniodes hamiltoni" parasitises only eastern rockhoppers. Cross contamination of the lice is not possible naturally due to the fact that chewing lice have limited mobility and heavily rely on their host for survival, meaning that the lice can only be transmitted across species by way of close physical contact. The northern rockhopper penguin feeds on krill and other sea life such as crustaceans, squid, octopus and fish. It breeds in
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