Colonization of the Yellow-legged gull in the southeastern Bay of Biscay and efficacy of deterring systems on landfill site

• Yellow-legged gulls from Spain have colonized SE Bay of Biscay since 2000.
• Deterring actions were used at the landfill site to control the bird population.
• Abundance of gulls decreased on the site but there is no change on the coastal distribution.
• One year later gulls no longer used the landfill for resting, scarcely for feeding.
• Impacts on distribution and future breeding are discussed.

On the French Basque Coast (southwest of France), the Yellow-legged gull Larus michahellis has undergone a widespread demographic and geographical increase in the last decade, originally by population breeding in northern Iberia. The demographic increase seems to be due to a combination of several factors: the establishment of a landfill close to the coast and the availability of nesting sites.Birds foraging on landfill sites affect day-to-day site operation. In recent years, thousands of gulls were present daily on the landfill site and have used waste as another feeding opportunity. Management methods were used to limit access of birds to the landfill site and to control the population to a natural dynamic. Distress calls and pyrotechnic means were used on the landfill site for 11 months. Abundance, behavior, efficacy of the deterring systems and distribution along the whole coast were studied.Initial results showed a significant decrease in the abundance of gulls on the landfill site. A change in their behavior was also noted with a reduction in resting and feeding birds. This, combined with the uninterrupted, random, deterring system at the landfill site showed an efficient measure to control gulls population. Monitoring along the coast did not show any significant impact on common resting sites.Despite these promising results, we cannot exclude a new opportunistic response from the gulls. In addition, the proximity of Spanish colonies requires cross-border management for effective control of the population. Long-term monitoring is needed both at the landfill site to measure possible habituation and at the nesting sites to assess breeding success after one year of deterring actions.