Southern Rockhoppers breed only in the Falkland Islands, Chile and Argentina, with 36 breeding sites in the Falklands and 15 sites in South America. Nests are made in large colonies high up on steep rocky cliffs. Two eggs of unequal size are laid in early November, but only the larger egg is generally successful. Chicks form small creches at 4 weeks of age, and fledge at 10 weeks in early February.
Adults generally remain within 40km of the nest site during the breeding season, feeding on small fish, squid and crustaceans at depths of up to 100 metres. Breeding sites are abandoned between April and October as birds migrate northwards. Adults do not begin breeding until 4 years of age, but can live to over 25 years. Sexes are similar in appearance.
The Falklands population crashed during the 1980s and early 1990s as a result of over-fishing. A census by the British Antarctic Survey in 1984 recorded a population of 2,500,000 pairs. A repeat census in 1995 showed a population of just 300,000 pairs, an 85% decline. The Falklands fishing industry was established in 1988. The population has since dropped to around 280,000 pairs.
The South American population has increased over this same period. Rockhoppers moved from the Falkland Islands to Argentina in order to avoid starvation.
The tiny population on Isla de los Estados in Argentina increased from just 50 pairs in 1996 to over 10,000 pairs by 1999. Isla de los Estados is the nearest Argentine colony to the Falkland Islands. Penguins moving from the Falklands to Argentina is the only way to explain a 200 fold increase in just four years, for a penguin that lays just one egg per year.
The decline of Falkland Islands penguins in the presence of a commercial fishing industry