Neonicotinoids impact all aspects of bird life: A meta-analysis

Worldwide, bird populations are declining dramatically. This is especially the case in intensely used agricultural areas where the application of neonicotinoid insecticides is thought to – unintendedly – cause a cascade of negative impacts throughout food webs. Additionally, there could be direct (sub-) lethal impacts of neonicotinoids on birds, but to date there is no comprehensive quantitative assessment to confirm or rule out this possibility. Therefore, we use a meta-analytical approach synthesizing 1612 effect sizes from 49 studies, and show that neonicotinoids consistently harm bird health, behavior, reproduction, and survival. Thus, in addition to reduced food availability, the negative direct effects of exposure to neonicotinoids likely contribute to bird population declines globally. Our outcomes are pivotal to consider in future risk assessments and pesticide policy: despite localized bans, the metabolites and residues of neonicotinoids remain present in the environment and in birds and will thus have long-lasting direct effects on both the individual and the population level.