Trophic niche variation throughout the year in the opportunistic Kelp Gull at different trophic scenarios in Patagonia, Argentina

LISNIZER, NORA; GATTO, ALEJANDRO; YORIO, PABLO

Congreso; 3rd World Seabird Conference; 2021

World Seabird Union

Seasonal foraging strategies are key determinants of seabird population dynamics. However, due to seabird dispersal after breeding, year-round trophic ecology studies rarely focus on individuals from known breeding colonies. In opportunistic seabirds, seasonal multi-colony trophic information is crucial to make links to demographic aspects at a regional scale and at metapopulation level. Using stable isotope analysis (δ15N, δ13C) of selected tissues (blood and primary feathers) we tested the trophic niche variation between the breeding and non-breeding periods in Kelp Gulls Larus dominicanus from three colonies with contrasting anthropic subsidies scenarios in coastal Patagonia, Argentina. Isotopic niche width, measured by means of multivariate ellipse-based metrics, was wider at all colonies during the non-breeding season. The colony with year-round availability of fisheries discards presented the lower isotopic niche width during both studied periods, compared to the other two colonies (one with fisheries discards only present a part of the year, the other without fisheries operating but with open dumps available all year). That colony is located at the coastal region with higher population growth rate compared to the other two, suggesting that fisheries discards used by gulls year round might have on effect on colony productivity. These results will help to orientate coastal management policies in this increasing Kelp Gull population scenario.