Data from: Risk assessment of pesticide seed treatment for farmland birds using refined field data

Due to reductions in winter food resources, newly sown cereal seeds have
become a key component of many bird species' diets, but these seeds
are often treated with pesticides that may cause toxic effects. To
complete an appropriate risk assessment, data on treated seed toxicity
need to be combined with information about the risk of exposure of birds
in the field and the factors that modulate such exposure. We studied the
abundance of pesticide-treated seeds available for birds in the field, the
pesticides and their concentrations in treated seeds, and the bird species
observed in the field that were feeding on these pesticide-treated seeds.
The exposure of red-legged partridge to treated winter cereal seeds was
characterized through the analysis of crop and gizzard contents of hunted
individuals (n = 189). Moreover, we measured the contribution of cereal
seeds in the autumn–winter diet of partridges in order to assess the
potential risk of exposure to pesticide-treated seeds. Density of treated
seeds on the soil surface after sowing (11·3 ± 1·2 seeds m−2 in the centre
of field and 43·4 ± 5·5 seeds m−2 in the headlands) was enough to provide,
in an area between 6 and 50 m2, doses of six active ingredients above
those indicating acute (i.e. a dose capable of killing 50% of individuals
of a sensitive species) and / or chronic (no observed effect level)
toxicity. Up to 30 bird species were observed consuming treated cereal
seeds in recently sown fields. Corn bunting was identified as an
appropriate focal passerine species for the risk assessment of
pesticide-treated seeds. We found that treated seeds were an important
route of pesticide ingestion for red-legged partridge; pesticide residues
(six fungicides and two insecticides) were found in 32·3% of crops and
gizzards. Cereal seeds represented more than half (53·4 ± 4·3%) of total
biomass consumed by partridges from October to February. Synthesis and
applications. The field exposure data combined with previous studies about
the toxicity to partridges of using pesticide-treated seeds point to an
unacceptable risk of this practice to farmland birds. Our results suggest
that the prophylactic use of pesticide-coated seeds should be avoided,
with the approval of this treatment considered on a case-by-case basis and
accompanied with specific measures to minimize risks of adverse effects on
avian communities.