Spatial and temporal variation in population trends of Kelp Gulls in northern Patagonia, Argentina

Abstract

Many populations of seabird species with opportunistic or generalist feeding habits have expanded worldwide, possibly because they are using additional food resources provided by human activities. The Kelp Gull (Larus dominicanus) is a generalist feeder that often feeds on 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 species of gull. However, population trends have been reported for only a few colonies and there has been no evaluation of population changes at a regional scale. In this study we provide an update on the distribution and size of Kelp Gull colonies along 1800 km of coastline of northern Patagonia, and assess population trends over a period of 15 years (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008) at different spatial scales (colony, coastal sector, region). In northern Patagonia, Kelp Gulls currently breed in 68 colonies, which range in size from a few to 11 000 breeding pairs. Ten new sites were colonised in the study period. Most colonies (74%) are increasing 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%), whereas the other two remained stable. Our results confirm the expansion of populations of Kelp Gulls along a long section of the coast of northern Patagonia, although the observed trends varied with the spatial scale considered.

Increasing breeding success of an Endangered penguin: artificial nests or culling predatory gulls?

“…Populations of many large gulls Larus spp. are increasing worldwide (Crawford et al 2009, Lisnizer et al 2011), due to cessation of control and/or increased human food subsidies, such as fisheries waste and open refuse tips (Bertellotti et al 2001, Yorio and Caille 2004). Gulls are often considered as an overabundant pest species (Blokpoel and Spaans 1991, Yorio et al 1998).…”

Demographic and Breeding Performance of a New Kelp GullLarus dominicanusColony in Patagonia, Argentina

“…Kelp Gulls are generalist and opportunistic feeders that take advantage of artificial food sources, such as fisheries discards and urban refuse (Yorio et al 2005). In Patagonia, Argentina, the Kelp Gull is the most abundant gull species (Yorio et al 1999), with an estimated total population of over 98,000 breeding pairs (Yorio et al 1998;Lisnizer et al 2011). Several studies have reported basic information about the size of Kelp Gull eggs (Williams et al 1984;Yorio and García Borboroglu 2002;Branco et al 2009).…”

Variation in the Size of Eggs of Kelp Gulls (Larus dominicarius) at Two Colonies in Patagonia, Argentina

“…Kelp Gulls are the most abundant seabird species breeding on the island; their numbers have increased from 6,300 to 9,200 breeding pairs between 1995 and 2006 (Yorio et al 1998;Lisnizer et al 2011). Similar or higher population trends were observed for other Kelp Gull colonies in that coastal sector (Lisnizer et al 2011). …”

“…In several seabird species, fishery waste has been shown to affect breeding parameters, including egg size (Oro 1999). Supplemental food in the form of fisheries discards and urban refuse has also been mentioned as a possible factor that has driven population increases in the San Jorge Gulf area during the last 2 decades (Lisnizer et al 2011).…”