Rockhopper penguin is one of the world’s most numerous penguin populations, it is estimated that the population declined by some 30 percent over the final 30 years of the 20th century. The cause of this decline is mainly unknown, but scientists have speculated that humans are involved, mostly by commercial overfishing, oil exploitation, and pollution. Recent research has shown that rockhopper penguin population declines with changes in ocean surface temperature, indicating a direct impact from climate change. These activities have depleted much of the rockhopper penguin’s food supply and raised the sea surface temperatures, and because this species is geographically isolated to
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