During the last European Ornithological Union Conference, held in Cluj (Romania), LIFE SALINAS team presented the poster “Socioeconomic impact and effects on biodiversity of the Yellow-legged Gull population in a Natural Park of SE Spain” about the current situation of the colonies of waterbirds in the San Pedro del Pinatar Saltpans.
The topic is basically whether the mitigation measures are effective on the control of the huge yellow-legged gull (YLG, Larus michahellis) population in San Pedro del Pinatar Saltpans. Culling has been carried out since 2001 and by removing the nests of the approximately 800 pairs that regulary breed in the saltpans area (without considering those that do so in the sourrandings –Encañizadas-). Despite the fact that the culling is not the ideal solution to solve the problems generated by this species, it does not seem very likely that the other 8 species of waterbirds that regularly breed in San Pedro did so in case of not acting. Particularly those smaller species such as Little Tern (Sternula albifrons) or Kentisth Plover (Charadrius alexandrinus) are favored by this measure as it considerably reduces predation rate and kleptoparasitism.
However, although thanks to the culling, other waterbird species are able to breed, this does not reduce the number of YLG individuals that visit the saltplans daily, which in some censuses is close to 4000. The presence of a bluefin tuna farm a few kilometers away, the trawling fleet or the open-air dumps are a very predictable and almost unlimited food resource. This is generating another indirect effect in the saltpans that is the fertilization of the soil due to the YLG faeces which has favored the development of dense shrubby vegetation and, therefore, a progressive reduction of the area available for colonial birds. In fact, although the number of breeding pairs of the colonial species (excluding the YLG) has not been decreased, the area through which these colonies are distributed has decreased from 406 ha in 1994 to 85.4 ha in 2016 which it means a reduction of 79 %.
Reference: Gustavo A. Ballesteros Pelegrín, Ángel Sallent and Julio F. Fernández Ramos. 2019. Socioeconomic impact and effects on biodiversity of the Yellow-legged Gull population in a Natural Park of SE Spain. XII EOU Conference. Cluj, Romania.