Seabird distribution on the Humboldt Current in northern Chile in relation to hydrography, productivity, and fisheries

Factors affecting seabird distribution in the Humboldt Current upwelling system in northern Chile were studied in January 1999 using ship transect counts. Of 24 species recorded, the Peruvian booby (Sula variegata), the kelp gull (Larus dominicanus) and the Humboldt penguin (Spheniscus humboldti) were the most abundant. Species composition varied among different areas of the system and distribution patterns differed substantially among eight of the more abundant species. Most species showed links to variation in environmental factors (trawler distribution, SST and chlorophyll concentration). Principal component analysis identified a feeding-flock factor as the most important one for explaining observed distribution patterns. One-third of all birds recorded were associated in feeding flocks and 3% of all individuals were directly attending fishing vessels.