Diet and Spatial Ecology Influence Red-Legged Partridge Exposure to Pesticides Used as Seed Treatment

Abstract

Seed treatment with pesticides is an extended agricultural practice with a high risk to granivorous birds that consume those seeds. To characterize that risk, it is necessary to understand the ecological factors that determine the exposure chances of birds to treated seeds. We investigated how pesticide uptake by red-legged partridges was related to cultivated plant ingestion and to the use of recently sown fields. We analyzed pesticide residues in 144 fecal samples from 32 flocks and determined the plant diet composition using DNA metabarcoding. Habitat use was studied through the monitoring of 15 GPS-tagged partridges. We confirmed, through the analysis of seeds, that >80% of cereal fields from the area had seeds treated with triazole fungicides. Tebuconazole was detected in 16.6% of partridges' feces. During the sowing season, cultivated plants accounted for half of the plant diet, but no association was found between cultivated plant consumption and pesticide intake. GPS tracking revealed that tebuconazole was detected in feces when partridges had recently used sown fields, whereas nonexposed partridges showed no overlap with recently sown areas. Our results highlight the need to incorporate field ecology into the characterization of pesticide exposure to improve the efficacy of environmental risk assessment.

Keywords: diet; farmland birds; pesticide exposure; spatial ecology; treated seeds.

Figure 1

Dot plots showing concentrations of tebuconazole in feces (red) and seeds (blue) samples (a) and flutriafol (b), prothioconazole (c), and piperonyl butoxide (d) concentrations measured in seed samples collected over the course of the study.

Figure 2

Relative read abundance (RRA %) with error bars ±SE of sequences corresponding to cultivated plant genera, resulting from the analysis of the two gene regions that were amplified for diet analysis: ITS2 (a) and rbcL (b). Different lower-case letters indicate significant (p < 0.05) differences between seasons according to least significant difference pairwise comparisons.

Figure 3

Spatial information for flocks (a) showing detectable pesticide residues in feces or (b) not showing detectable pesticide residues in feces. The figure shows the estimated circular home range areas around the centroids of plots from which partridge feces were collected, adjusted to the minimum, mean, and maximum surface areas of the estimated MCP of animals (see Figure S3). Note the overlap of circular areas (home ranges) with recent plot sowing (within the last 15 days). Letters and numbers refer to the flock IDs. Details on the % overlap with sown fields and on the time since the sowing day in each case are given in Table S6.