Farmland birds are declining across Europe and North America and the research of factors behind is the subject of extensive researches. Agricultural intensification is now recognized as a major factor governing the loss of biodiversity with strong evidence that pesticides induced direct bird mortality at a high dose. However, less attention has been given to the long-term effects of chronic exposure to low dose of pesticides. Here, we used an experimental procedure in which grey partridges were fed with untreated grains obtained from either organic (no pesticide) or conventional agriculture (with pesticide) for 26 weeks, thus strictly mimicking wild birds foraging on fields. We then examined a suite of life-history traits (ecophysiological and behavioural) that may ultimately, influence population dynamics. We show for the first time that ingesting low pesticide doses over a long period has long-term consequences on several major physiological pathways without inducing differential mortality. Compared to control partridges, birds exposed to chronic doses i) had less developed carotenoid-based ornaments due to lower concentrations of plasmatic carotenoids, ii) had higher activated immune system, iii) showed signs of physiological stress inducing a higher intestinal parasitic load, iv) had higher behavioural activity and body condition and v) showed lower breeding investment. Our results are consistent with a hormetic effect, in which exposure to a low dose of a chemical agent may induce a positive response, but our results also indicate that breeding adults may show impaired fitness traits bearing population consequences through reduced breeding investment or productivity. Given the current scale of use of pesticides in agrosystems, we suggest that such shifts in life-history traits may have a negative long-term impact on wild bird populations across agrosystems. We stress that long-term effects should no longer be ignored in pesticide risk assessment, where currently, only short-term effects are taken into account.

在欧洲和北美，农田鸟类正在减少，其背后因素的研究是广泛研究的主题。农业集约化现已被认为是控制生物多样性丧失的主要因素，有力的证据表明，农药会导致高剂量直接导致鸟类死亡。但是，对长期暴露于低剂量农药的长期影响的关注较少。在这里，我们使用了一个实验程序，将灰色part饲喂未经处理的谷物，这些谷物是从有机（无农药）或常规农业（有农药）获得的，为期26周，因此严格模拟了野禽在田间觅食。然后，我们研究了可能最终影响人口动态的一系列生活史特征（生态生理和行为）。我们首次表明，长期摄入低剂量的农药会对几种主要的生理途径产生长期影响，而不会引起不同的死亡率。与对照part相比，暴露于长期剂量的鸟类i）由于血浆类胡萝卜素的浓度较低，其类胡萝卜素的装饰物不太发达，ii）具有较高的激活的免疫系统，iii）表现出生理压力的迹象，导致较高的肠道寄生虫负荷，iv ）具有较高的行为活动和身体状况，且）具有较低的育种投资。我们的结果与药效相吻合，其中接触低剂量的化学物质可能会引起阳性反应，但是我们的结果也表明，成年成年后可能会降低成年投资或提高生产率，从而导致成年后适应性状受损，从而给种群带来后果。鉴于目前在农业系统中使用农药的规模，我们建议这种生活史特征的转变可能会对整个农业系统中的野生鸟类种群产生长期的负面影响。我们强调，在农药风险评估中，长期影响不应再被忽略，目前仅考虑短期影响。