Effect of Fertigated Water Consumption on the Immune Responsiveness and Antipredator Behavior of Red-Legged Partridge Chicks

Fertigation practices are common in dry agricultural areas, and nitrate exposure through fertigation water consumption could pose significant risks to farmland birds. This study simulated a realistic exposure scenario to evaluate the effects of drinking nitrate-contaminated water on the growth, physiology, and antipredator behavior of red-legged partridge (<i>Alectoris rufa</i>) chicks. Hatchlings were exposed to two nitrate concentrations commonly used in fertigation (100 and 500 mg/L) through <i>ad libitum</i> drinking water over a 28-day period. Nitrate exposure at both concentrations increased chick weight and elevated hematocrit levels, possibly as a compensatory response to nitrate-induced methemoglobinemia. Additionally, it reduced cell-mediated immune responsiveness, indicating a compromised immune function. We simulated aerial and terrestrial predator attacks (raptor and fox) and evaluated behavioral responses of exposed and control chicks. We report nitrate effects on antipredator responses, specifically reduced fleeing distances, altered freezing, and active escape behaviors, which would increase predation risk in the wild. These findings highlight new threats associated with nitrate contamination in agricultural landscapes, particularly for exposed birds that rely on irrigation water during the summer months. This study emphasizes the need to assess the sublethal effects of nitrates in high-exposure scenarios to improve environmental risk assessments and mitigate risks contributing to the population declines in farmland species.