Neonicotinoids still present in farmland birds despite the ban 

Neonicotinoids (commonly shortened to neonics) are a class of neuro-active insecticides, chemically similar to nicotine, developed in the 1980s. They are the most widely used insecticides worldwide and are considered to be of low risk to non-target organisms such as vertebrates. Further, they are reported to be rapidly excreted and metabolized, reducing their potential toxicity. There has long been concern that they are a contributing factor in the decline of bee colonies; but growing evidence of adverse effects on farmland bird species raises questions about the purported harmless nature of these pesticides. A French study attempted to search for pesticide residues in bird species of different food-chain levels and at different life stages, by using multiple bird monitoring programs. Three passerine birds, the blackbird, cirl bunting, and common nightingale that feed on seeds and invertebrates, were monitored during their reproductive period; and the grey partridge that feeds on seeds was monitored during its wintering period. They also monitored chicks of an apex predator, the Montagu’s harrier, that preys mostly upon common voles but also upon insects.

The study site is located in southwestern France in the Long-Term Socio-Ecological Research Zone, a 450 km2 area where the soil occupancy and the agricultural practices have been monitored each year since 1994. In this intensive farming area, winter cereal crops accounted for ∼41% (wheat: 33.8% and corn: 9.6%) of the area under cultivation; in addition, there were sunflowers (10.4%), oilseed rape (8.3%) etc. In France, neonics have been banned for outdoor use and in pharmaceutical products since September 2018, except for emergency authorized use on sugar beet crops. The use of neonics is still allowed in veterinary medicine eg for anti-tick medication.

The study found that the birds’ blood samples showed presence of residues of five neonics: three banned since 2018 in France—clothianidin, thiacloprid, and thiamethoxam—and two—dinotefuran and nitenpyram—used for veterinary purposes only. While none of these neonics was detected in blackbirds, all were present in grey partridges. Clothianidin was detected in all species, except blackbirds. Concentrations of the three banned neonics were similar or higher than concentrations found in birds monitored elsewhere before the ban. These findings raise questions about the persistence of neonics within the environment and the mode of exposure to wild fauna. Future investigations on the sublethal effects of these neonics on life-history traits of these farmland birds are required to provide a better understanding of the effects of exposure of bird populations to these insecticides.

In September 2019, the University of Saskatchewan published results from the first experiment to track the effects of a neonicotinoid pesticide on birds in the wild. The study found that white-crowned sparrows who consumed small doses of an insecticide called imidacloprid suffered weight loss and delays to their migration—effects that could severely harm the birds’ ability to survive and reproduce. The doses were well within the range of what a bird could realistically consume in the wild—equivalent to eating just a few treated seeds.

In UK, on 23rd January 2023, the Minister for Agriculture approved a temporary use exemption for a a banned pesticide (Cruiser SB) to be used on sugar beet in 2023. This pesticide will be applied to seed as a dressing before planting if a high aphid count is expected. Aphids carry a virus known as Yellows which adversely affects some crops.

Sources :

Neonicotinoids: Still present in farmland birds despite their ban  Elva Fuentes, Agathe Gaffard , Anaïs Rodrigues , Maurice Millet , Vincent Bretagnolle , Jérôme Moreau , Karine Monceau  – Chemosphere, Volume 321, April 2023, 138091