Population changes and demography of the Northern Rockhopper Penguin on Amsterdam and Saint Paul islands

We investigated changes in population size and demography of the Northern R ockhopper Penguin (Eudyptes chrysocome moseleyi) between 1971 and 1995 on A msterdam and Saint Paul islands. During an intensive survey between 1993 an d 1995, breeding success was similar to that reported from other sites, alt hough the first egg (A-egg) loss rate was lower on Amsterdam Island than at other localities. The mean age of first return to the breeding site and of first reproduction were respectively (X) over bar = 4.2 +/- SD of 2.1 year s and (X) over bar = 4.7 +/- SD of 1.7 years. The adult survival rate, calc ulated between 1988 and 1993, was significantly lower one year after bandin g [(X) over bar = 72.2 +/- SD of 1.6%] than in subsequent years [(X) over b ar = 84.0 +/- SD of 1.1%] due to the effect of banding. Immature survival r ate was estimated at 39% during the first year after banding. Two birds ban ded as chicks have been found in Australia, suggesting that immatures winte r off Souther Australia. The population on Amsterdam Island decreased at a rate of 2.7% per year bet ween 1971 and 1993. Using the demographic parameters measured, we calculate d a modelled rate of increase of 0.943. Between 1982 to 1993, mean sea surf ace temperature near Amsterdam and Saint Paul islands decreased significant ly, and this change was significantly related to the decline of Amsterdam I sland population during the same period. Mean sea surface temperature decli ne could affect the Rockhopper Penguin population through changes of distri bution and abundance of prey. Other factors such as the large increase of t he Sub-Antarctic Fur Seal population at Amsterdam Island between 1971 and 1 993 could have reduced the penguin population. Between 1971 and 1993, the S aint Paul population of penguins increased by 5.5% per year, but this is no t significantly related to the mea sea surface temperature decrease. This s mall Rockhopper Penguin population may still be recovering to its level bef ore exploitation in the 1930s.