Winter dispersal of rockhopper penguins Eudyptes chrysocome from the Falkland Islands and its implications for conservation

In 3 successive years (1998 to 2000), the winter migration of rockhopper penguins Eudyptes chrysocome from 3 separate breeding colonies on the Falkland Islands was monitored using satellite transmitters. After their moult, 34 penguins were followed for a mean transmission period of 81 +/- 21 d. While there were substantial spatial and temporal variations in migration patterns, we identified several foraging areas where food availability is presumably higher than elsewhere. Coastal areas of the Falkland Islands and South America appeared to provide a sufficient food supply, and many penguins commuted between these 2 areas, which are about 600 km apart. Rockhopper penguins from northern breeding colonies also used areas along the slope of the Patagonian Shelf up to 39degreesS, about 1400 km northwards. By contrast, only a few birds from the southern breeding colony migrated to the Burdwood Bank, which is situated about 250 km to the south of the Falkland Islands, and adjacent oceanic waters. None of the penguins in this study left the maritime zone of the Falkland Islands in an easterly direction to forage in oceanic waters. The mean distances covered per day by individual birds varied greatly, depending on the phase of the foraging trip. The overall mean travelling speed was 26 km d(-1) (range: 13 to 45 km d-1). Inter-annual variation was evident both in the use of different foraging areas, and also in the time at which the winter migration began. In 1998 and 2000, penguins from Seal Bay and Sea Lion Island left their breeding colony within 1 wk after being equipped with transmitters and did not return, whereas in 1999 most penguins made short foraging trips and returned repeatedly to their colonies for periods of up to 100 d. Potential threats to the rockhopper penguins during their winter migration, resulting from human activities such as fishing and oil pollution within the Falkland Islands maritime zone and the Argentine Exclusive Economic Zone, are discussed.