Behavioral Responses of Imidacloprid-Dosed Farmland Birds to a Simulated Predation Risk.

Sublethal exposure to imidacloprid and other neonicotinoid insecticides may affect the neurological functions of birds. As such, behavior may be compromised. Here, we tested experimentally the effects of 1 and 6 mg/kg bw of imidacloprid on the antipredator behavioral responses of the red-legged partridge (Alectoris rufa) to simulated predator threats. Sixty-six partridges were challenged in groups or individually to intra- and interspecific alarm calls, to a raptor silhouette (aerial predation risk), and to a fox model (terrestrial predation risk). Antipredator behaviors were recorded as active (escape, active vigilance) and passive (passive vigilance, crouching, and freezing) responses. Latency in response to the stimuli, percentage of individuals who responded, response duration, speed of active responses, and vocalizations were measured. In experiments with partridges in the group, crouching against simulated predation risk lasted less time in birds treated with 6 mg a.i./kg bw than in control birds. In the experiments with individual partridges, passive vigilance against the intraspecific alarm lasted longer in birds treated with 6 mg a.i./kg bw than in control birds. The observed hyperreactivity to the predatory threat after a sublethal imidacloprid exposure can have consequences on survival under field conditions, where predation is a main driver of population dynamics.

Field Availability and Avoidance of Imidacloprid-Treated Soybean Seeds and Cotyledons by Birds.

Treated seeds and their cotyledons can present a toxicological risk to seed-eating birds. To assess whether avoidance behavior limits exposure and consequently the risk to birds, three fields were sown with soybeans. Half of the surface of each field was sown with seeds treated with 42 g/100 kg seed of insecticide imidacloprid (T plot, treated) and the other half with seeds without imidacloprid (C plot, control). Unburied seeds were surveyed in C and T plots at 12 and 48 h post-sowing. Damaged seedlings were surveyed in C and T plots at 12 days post-sowing. The abundance and richness of birds was surveyed at the field level (without distinguishing between C and T plots) before, during, and after sowing, and 12 days post-sowing. Unburied seed density was higher in the headlands of the T plots than in the C plots, but did not differ between 12 and 48 h. The damage to cotyledons of seedlings was 15.4% higher in C plots than in T plots. The abundance and richness/ha of birds that eat seeds and cotyledons were lower after sowing, indicating a deterrent effect on birds by sowing imidacloprid-treated seeds. Although the variation in seed density over time does not allow solid conclusions to be drawn about the avoidance of seeds treated by birds, the seedling results suggest an aversive effect of imidacloprid-treated soybeans on birds. The dominant species was the eared dove (Zenaida auriculata), whose risk of acute poisoning by imidacloprid in soybean seeds and cotyledons was low, according to its toxicity exposure ratio, foraged area of concern, and foraged time of concern. Environ Toxicol Chem 2023;42:1049-1060. © 2023 SETAC.