SEASONAL DECLINE IN BREEDING PERFORMANCE OF THE KELP GULL Larus dominicanus

GARCÍA BORBOROGLU, PABLO; YORIO, PABLO; MORENO, JUAN; POTTI, JAIME

Marine Ornithology

Pacific Seabird Group on behalf of a consortium of seabird groups: African, Australasian, Dutch, Pacific and UK.

Lugar: Melbourne, Australia; Año: 2008

The effects of timing of breeding on reproductive parameters of Kelp Gulls Larus dominicanus were studied in Patagonia, Argentina, during 1998 and 1999. Yearly and spatial variation in the study were included by sampling nests during two field seasons and in different areas within the colony, and accounted for variation with respect to breeding synchrony and breeding density. In both years and three study areas, individuals laying earlier had a higher hatching success, larger number of chicks fledged and higher breeding success. Study area within the colony and year had significant effects only on breeding success and number of chicks fledged. A similar relationship with laying date was observed for the size of month-old first chicks. No effects of breeding synchrony on breeding parameters were detected. Timing of breeding, independently of study year and area, had no effect on either clutch size or egg size. Our results document for the first time the seasonal decline in breeding performance in the Kelp Gull, a species widely distributed in the Southern Hemisphere.