Rockhopper penguin Rockhopper penguin The rockhopper penguins are three closely related taxa of crested penguins that have been traditionally treated as a single species and are sometimes split into three species. Not all experts agree on the classification of these penguins. Some consider all three as distinct species, some split the western and eastern forms into the southern rockhopper penguin and keep the northern rockhopper as distinct, while other experts consider all three potential varieties to be one species. Rockhopper penguins are among the smaller species of penguin. They range from 3 inches to 6 where males are larger than females. After
Northern rockhopper penguin drop in the population at Gough Island has been described as equivalent to the loss of 100 birds every day since the 1950s. A study published in 2009 showed that the world population of the northern rockhopper had declined by 90% since the 1950s, possibly because of climate change, changes in marine ecosystems and overfishing for squid and octopus by humans. Other possible factors in the decline include disturbance and pollution from ecotourism and fishing, egg-harvesting, and predation and competition from subantarctic fur seals ("Arctocephalus tropicalis"). Surveys show that the birds are at risk of infection by goose barnacles. House