How does a generalist seabird species use its marine habitat? The case of the kelp gull in a coastal upwelling area of the Humboldt Current

The distribution of kelp gulls (Larus dominicanus) was studied by ship-based transect counts in the SE Pacific Ocean off Chile, South America. Some 96-98% of the kelp gulls were in a band less than 20 km from the coast, mainly near the breeding colony on Pijaros Island and the City of Coquimbo. Abundance did not change significantly among years, but was influenced significantly by distance to land. Principal component analysis yielded two components that jointly explain 53% of the standardized variance. The first (explaining 36% of the variance) includes distance to the nearest coast and water depth, the second (17%) associates with the presence of fishing vessels. The results suggest that the stability of the summer distribution of kelp gulls is generated by the large and semi-permanent offer of food at fish markets and city sewage works, as well as the location of the breeding colonies. Further analysis on other temporal scales (seasonal, decadal) associated with reproductive or non-reproductive changes within the population and/or ENSO cycles will be necessary to confirm the multiscale stability of the pattern described.