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 vocalization and prevent an energetically costly fight . In birds with song repertoires, individuals may share the same song type and use these song types for more complex communication. Some birds will respond to a shared song type with a song-type match (i.e. with the same song type). This may be an aggressive signal, however results are mixed. Birds may also interact using repertoire-matches, wherein a bird responds with a song type that is in its rival's repertoire but is not the song that it is currently singing. This may be a less aggressive act than song-type matching. Communication through bird