Agricultural pesticides usage has been increasing globally. These compounds have been developed to disrupt pest species physiology, but because their specificity is limited, they can also have adverse effects on non-target organisms. Recent studies have shown that the damaging toxicological effects of pesticides can be amplified in stressful environments. However, few studies have documented these effects in natural settings where organisms are simultaneously exposed to pesticides and to other environmental stressors such as parasites. In this study, we assessed both pesticide and ectoparasite effects on the physiology of a free-ranging bird. We measured physiological markers including haematocrit, bacteria-killing ability (BKA) and leucocyte counts, as well as exposure to haematophagous Protocalliphora larvae, in tree swallow nestlings (Tachycineta bicolor), a declining aerial insectivore, in southern Québec, Canada, for over 3 years. We found that combined exposure to pesticides and Protocalliphora larvae was negatively related to haematocrit, suggesting possible synergistic effects. However, we found no such relationships with BKA and leucocyte counts, highlighting the complexity of physiological responses to multiple stressors in natural settings. Populations of several aerial insectivores are declining, and although sublethal pesticide effects on physiology are suspected, our results suggest that exposure to other factors, such as parasitism, should also be considered to fully assess these effects, especially because pesticides are increasingly present in the environment.

中文翻译：

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农业杀虫剂和体外寄生虫：对日益减少的空中食虫动物生理的潜在综合影响

全球农业农药的使用量一直在增加。这些化合物的开发目的是破坏害虫物种的生理机能，但由于其特异性有限，它们也会对非目标生物体产生不利影响。最近的研究表明，农药的破坏性毒理学作用在压力环境中会放大。然而，很少有研究记录生物体同时暴露于农药和其他环境压力源（如寄生虫）的自然环境中的这些影响。在这项研究中，我们评估了农药和体外寄生虫对自由放养鸟类生理的影响。我们测量了加拿大魁北克南部树燕雏鸟 (Tachycineta bicolor) 的生理标志物，包括血细胞比容、杀菌能力 (BKA) 和白细胞计数，以及与吸血原毛虫幼虫的接触情况，树燕雏鸟是一种日渐衰落的空中食虫动物，超过 3 年的时间年。我们发现农药和原毛丽虫幼虫的联合暴露与血细胞比容呈负相关，这表明可能存在协同效应。然而，我们发现 BKA 和白细胞计数没有这种关系，这凸显了自然环境中对多种压力源的生理反应的复杂性。几种空中食虫动物的数量正在下降，尽管怀疑农药对生理有亚致死的影响，但我们的结果表明，还应考虑暴露于其他因素，例如寄生，以充分评估这些影响，特别是因为农药越来越多地存在于环境中。