Spatial and temporal variations in kelp gull population trends in northern Patagonia, Argentina

LISNIZER, N.; GARCÍA BORBOROGLU, P.; YORIO, P.

EMU

CSIRO PUBLISHING

Año: 2011 vol. 111 p. 259 - 267

0158-4197

Many populations of seabird species with opportunistic feeding habits have expanded worldwide potentially related to their use of supplementary food sources provided by human activities. The Kelp Gull (Larus dominicanus) is a generalist feeder that often utilizes urban and fish waste and its populations have been expanding in several regions of the Southern Hemisphere. In Patagonia, Argentina, it is the most abundant gull species, however, population trends have been reported for only a few colonies. No evaluations have yet considered population changes at the regional scale. In this study we update information on the distribution and size of Kelp Gull colonies along 1 800 km of coast in northern Patagonia, and assess its population trends over a 15-year period (1994 – 2008) at different spatial scales (colony site, coastal sector, region). Kelp Gulls currently breed in 68 colonies which range in size from a few to 11 000 breeding pairs. Ten new sites were colonized in the study period. Most colonies (74%) show increasing trends and the overall population increased by 37% (from 52 784 to 72 616 pairs), at an annual growth rate of 2.7%. Two of the four coastal sectors showed significant annual increases (5%) and the other two remained stable. Our results confirm the expansion of Kelp Gull populations along a wide coastal region in northern Patagonia, although the observed trends varied depending on the spatial scale considered