Weak recovery of insectivorous bird populations after ban of neonicotinoids in France, hinting at lasting impacts.

Neonicotinoids are expected to play a significant role in the decline of bird populations through their adverse effects on food resources (primarily insects) and their lethal and sub-lethal toxicity. Previous studies in the US and the Netherlands have shown links between neonicotinoid use and bird abundance, but the potential for population recovery after ban has not been investigated. Here, we investigated this relationship in France over the 2013-2022 period, focusing on 57 bird species from insectivorous, granivorous and generalist guilds, surveyed across a large number of plots (n = 1983). We specifically examined imidacloprid, the most widely sold neonicotinoid in France before its ban in 2018, which is still found in surface waters and soils. Additionally, we accounted for potential effects of other pesticides by calculating the Total Applied Toxicity (TAT) for different species groups, as well as landscape and climate factors. We found that population abundance of insectivorous birds was negatively associated with imidacloprid use. We also found that the difference in insectivorous bird abundance between sites with high versus no imidacloprid use was slightly higher before the ban (12.7 % more birds in sites with no imidacloprid) than after (9 %), suggesting only weak recovery of their populations. In contrast, granivorous and generalist species showed neutral or non-linear associations with other pesticide use and no response to imidacloprid. Our study confirms the detrimental impact of imidacloprid on insectivorous birds and highlights that pesticide bans alone do not ensure immediate biodiversity recovery. This calls for additional conservation actions in landscapes contaminated with neonicotinoids to restore insect and bird populations.