A new concept based on analysis of dive depth data was developed to help estimate prey consumption in ten free-ranging Magellanic penguins (Spheniscus magellanicus) that were brooding chicks. By simultaneously analysing the undulations in the dive depth profile (measured by time-depth recorders, TDRs) and beak opening (obtained from the recently developed intra-mandibular angle sensors, IMASEN), it was possible to determine the proportions of the undulations in the dive profile that resulted (or not) in prey capture. This methodology allowed the number of prey consumed to be estimated with a mean error of 10±6% using TDR data alone. If the mean mass of prey is known, then the overall mass of prey consumed per unit time can be determined. Additionally, the method allows estimation of the depth at which prey is taken and thus indicates how penguins exploit the water column. Due to its simplicity, the proposed methodology has applications for other Spheniscus penguin species and should be considered for other marine endotherm divers that show undulations in the dive depth profile.

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Between 1999 and 2003 we collected information on the breeding distribution and abundance of 12 seabird species occurring on nine islands off the coasts of north and central Chile (27°-33° S). The Peruvian booby Sula variegata was the most abundant seabird with a breeding population of ca. 18,000 pairs concentrated in two islands, followed by the Humboldt penguin Spheniscus humboldti with ca. 9,000 pairs, the largest colony being at Chañaral Island with ca. 7,000 pairs. Kelp gulls Larus dominicanus bred at all the surveyed sites in colonies of variable size, ranging from 40 to 2,000 pairs. Peruvian diving-petrels Pelecanoides garnotii and Peruvian pelicans Pelecanus occidentalis bred at restricted sites, but generally in large colonies. Magellanic penguins Spheniscus magellanicus, wedge-rumped storm-petrels Oceanodroma tethys, Neotropical cormorants Hypoleucos brasiliensis, guanay cormorants Leucocarbo bougainvillii, red-legged cormorants Stictocarbo gairmardi, band-tailed gulls Larus belcheri and Inca terns Larosterna inca nested at few sites forming small colonies (from a few to 150 pairs). Two new breeding sites are reported for the Peruvian diving-petrel and nesting of the wedge-rumped storm-petrel is confirmed on the Chilean coast for the first time. Despite protective status, most of the islands showed human disturbance, derived mainly from guano harvesting, egging and tourism. On at least five of these islands we were able to confirm introduced mammals including rats, rabbits and cats. These factors are likely to be detrimental to seabirds and thus demand detailed assessment. Further comprehensive ornithological surveys in other areas are needed so as to improve the scarce knowledge that we currently have on the seabird populations along the Chilean coast.Key words: seabirds, breeding colony, abundance, conservation, Humboldt Current, Chile. RESUMENEntre 1999 y 2003 obtuvimos información sobre la distribución reproductiva y abundancia de 12 especies de aves marinas en nueve islas frente a las costas del norte y centro de Chile (27-33° S). El piquero Sula variegata fue la especie más abundante con una población reproductiva de 18.000 parejas, concentrada principalmente en dos islas. La segunda especie más abundante fue el pingüino de Humboldt Spheniscus humboldti con ca. 9.000 parejas, siendo isla Chañaral la colonia más grande con ca. 7.000 parejas. La gaviota dominicana Larus dominicanus nidificó en todas las islas formando colonias que variaron desde 40 a 2.000 parejas. Yuncos Pelecanoides garnotii y pelícanos Pelecanus occidentalis nidificaron en pocos lugares, pero formando grandes colonias. El pingüino de Magallanes Spheniscus magellanicus, la golondrina de mar peruana Oceanodroma tethys, el yeco Hypoleucos brasiliensis, el guanay Leucocarbo bougainvillii, el lile Stictocarbo gaimardi, la gaviota peruana Larus belcheri y el gaviotín monja Larosterna inca nidificaron en colonias pequeñas (1 a 150 parejas) y en pocos lugares. Se encontraron dos nuevos sitios de nidificación de yunco y se confir...

The Humboldt penguin, once common throughout its range, is today listed as Vulnerable by the IUCN. Mark-recapture and telemetry studies indicate that adult Humboldt penguins are sedentary, suggesting strong genetic differentiation between colonies. We developed genotypes for 336 individuals at 12 microsatellite loci sampled at four different localities spanning the entire range of this species. Results show that long-term gene flow has occurred but appears to be affected by geographic distance as pairwise F ST comparisons involving the colony at Punta San Juan (Peru) and the two colonies at Algarrobo (central Chile) and Puñihuil (southern Chile) are significant. Bayesian estimates of recent migration rates indicate substantial dispersal among all colonies. Despite the dramatic decline in numbers, we did not observe a bottleneck in any population. Furthermore, we did not detect a founder effect in the recently discovered colony at Puñihuil. As our indirect estimates signal strong gene flow between populations, we suggest that Humboldt penguin colonies need to be managed as a metapopulation rather than as discrete management units.