Re-evaluation of historical rockhopper penguin population data in the Falkland Islands

Over the past 70 years, three counts have been conducted on the Rockhopper Penguin (Eudyptes chrysocome) population on the Falkland Islands during the 1932/33, 1995/96 and 2000/01 breeding seasons. The results indicated a population decrease of more than 90% during this period, from more than three million breeding pairs in 1932/33 to less than 300,000 breeding pairs in the mid-1990s. However, a re-evaluation of these data revealed that the original population was substantially overestimated and the 1930s numbers were probably closer to 1.5 million breeding pairs. Modifications to the mid-1990s data produce a revised population estimate of about 263,000, rather than 297,000 breeding pairs. Based on these revised values, the overall decrease in the Rockhopper Penguin at the Falkland Islands between 1932 and 1995 still exceeded 80%, at a rate of ca. 2.75% per annum. In the most recent census, the population was estimated to be 272,000 breeding pairs, suggesting a stable population since the mid 1990s. These re-calculations of historical Rockhopper Penguin population trends in the Falkland Islands have important implications for the assessment of the global population size and long-term trends of this species.

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