Rockhopper penguin penguins in different areas. Northern Penguins begin the mating process two months earlier than Southern ones. Two eggs are usually laid a few days apart during early November in hope that at least one will survive, and the second egg is usually larger than the first. They will use the same nest as they did in previous years as well. Eggs hatch about a month later and the mother will have food for the chick. There are currently 19 species and six genera of living penguins. The rockhopper penguin has 3 subspecies: "Eudyptes filholi", the Eastern Rockhopper; "Eudyptes mosleyi", the
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