SATELLITE TRACKING OF HUMBOLDT PENGUINS (SPHENISCUS-HUMBOLDTI) IN NORTHERN CHILE

During the El Nino of 1982/1983, the Humboldt penguin population dimin ished dramatically in the whole distributional area of the species. Re covery of the population was slow since 1983 and it has been suggested that large numbers of Humboldt penguins die at ,sea, entangled in net s, or starve to death, even during non-''EI Nino'' years. We were able to determine for the first time, how Humboldt penguins on Pan de Azuc ar Island (26 degrees S; 72 degrees W) utilize their marine habitat an d where their feeding areas lie. For this purpose we employed two stre amlined Argos satellite transmitters during the 1994/1995 and 1995/199 6 breeding seasons, respectively. Mean travelling speed of Humboldt pe nguins during foraging trips was 0.94 m s(-1) and 50% of bird position s were located within 5 km of the island (90% within 35 km). Total are a covered by Humboldt penguins foraging from Pan de Azucar Island was 12255 km(2). Satellite transmitters also recorded dive duration; pengu ins spent on average 7.8 to 9 h diving per foraging day but. showed no preferences for particular feeding areas. Mean daily dive durations ( 4-d mean) recorded during the 1994/1995 breeding season were positivel y correlated between birds. Significant correlation between dive durat ion and sea surface temperature anomalies and negative correlation bet ween dive duration and fishery landings at nearby Caldera harbour indi cate that the 1994/1995 increase in foraging effort was a response to deteriorating prey availability. Sea surface temperatures during the 1 995/1996 breeding season were colder than average, and we observed no trends in bird diving activities.