Exploiting the anthropocene: Behavioral adaptation by an opportunistic raptor to landfill sites and its implications for conservation

Abstract Landfills are ubiquitous around the world, providing superabundant trophic resources for wildlife, which involves different ecological trade-offs between costs and benefits. Several species have established a dependence on landfills at the population level (i.e., dependence scenario), whereas other species or populations may use landfills opportunistically as an additional or secondary trophic resource (i.e., opportunism scenario). Here, we provide a comprehensive analysis of the influence of landfills on the spatial behavior of Milvus migrans (Black Kite), an opportunistic, trans-Saharan migratory raptor from the Western Palearctic. We GPS-tagged 25 Spanish kites to estimate the use of landfills by the species and to investigate their influence on the spatial behavior of this raptor. We found that the overall use of landfills was generally loose during the annual period (median value = 0.1 hr day−1), being scarce and sporadic during the breeding period, and significantly higher during migratory periods. Landfill use was not triggered by poor habitat conditions, suggesting that the individuals did not actively compensate environmental deficiencies with landfills refuse. In addition, we did not find any other significant effect of landfills on movement-related parameters, such as daily travelled distance, foraging activity, energy expenditure, or shape and length of migration. In conclusion, the behavior of Spanish M. migrans is more consistent with the opportunism scenario—landfills confer some strategic advantages as predictable and abundant food sources, especially during highly demanding periods such as migration, but do not strongly determine the behavior and life cycle of this population at least at short or medium term. Despite the relatively low use of landfills by Spanish M. migrans, the population may still be vulnerable to risks associated with landfills (e.g., plastic ingestion, accumulation of heavy metals, or collisions). However, from a spatial ecology perspective, our study did not find that the closure or modification of open-up landfills will have a long-term effect on the Iberian breeding population.