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

TL;DR

This study shows that drinking nitrate-contaminated water affects the health and predator-avoidance behaviors of red-legged partridge chicks.

Contribution

The study reveals new sublethal effects of nitrate exposure on bird physiology and behavior, important for environmental risk assessments.

Findings

Nitrate exposure increased chick weight and hematocrit levels, possibly due to methemoglobinemia.

Exposure reduced cell-mediated immune responsiveness and altered antipredator behaviors like fleeing and freezing.

Behavioral changes increase predation risk in wild populations.

Abstract

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 (Alectoris rufa) chicks. Hatchlings were
exposed to two nitrate concentrations commonly used in fertigation
(100 and 500 mg/L) through ad libitum 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.

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