In the context of increasing global environmental changes, it has become progressively important to understand the effects of human activity on wildlife populations. Declines in several avian populations have been observed since the 1970s, especially with respect to many farmland and grassland birds, which also include some aerial insectivores. Changes in farming practices referred to as agricultural intensification coincide with these major avian declines. Among those practices, increased pesticide use is hypothesized to be a key driver of avian population declines as it can lead to both toxicological and trophic effects. While numerous laboratory studies report that birds experience acute and chronic effects upon consuming pesticide treated food, little is known about the effects of the exposure to multiple pesticides on wildlife in natural settings. We monitored the breeding activities of Tree Swallows (Tachycineta bicolor) on 40 farms distributed over a gradient of agricultural intensification in southern Québec, Canada, to evaluate the presence of pesticides in their diet and quantify the exposure effects of those compounds on their reproductive performance between 2013 and 2018. We first assessed the presence of 54 active agents (or derivatives) found in pesticides in 2,081 food boluses (insects) delivered to nestlings by parents and documented their spatial distribution within our study area. Second, we assessed the effect of pesticide exposure through food (number of active agents detected and number of contaminated boluses on a given farm for a given year, while controlling for sampling effort) on clutch size as well as hatching and fledging successes and nestling’s mass upon fledging. Pesticides were ubiquitous in our study system and nearly half (46%) of food boluses were contaminated by at least one active agent. Yet we found no relationship between our proxies of food contamination by pesticides and Tree Swallow reproductive performance. More studies are needed to better understand the putative role of pesticides in the decline of farmland birds and aerial insectivores as potential sublethal effects of pesticides can carry over to later life stages and impact fitness.

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评估农药暴露对下降的空中食虫动物繁殖性能的影响

在全球环境变化日益加剧的背景下，了解人类活动对野生动物种群的影响变得越来越重要。自 1970 年代以来，已经观察到若干鸟类种群数量下降，尤其是许多农田和草原鸟类，其中还包括一些空中食虫动物。被称为农业集约化的农业实践的变化与这些主要的禽类减少同时发生。在这些做法中，农药使用的增加被假设是鸟类数量下降的关键驱动因素，因为它会导致毒理学和营养学影响。虽然许多实验室研究报告说，鸟类在食用经过杀虫剂处理的食物后会经历急性和慢性影响，关于在自然环境中接触多种杀虫剂对野生动物的影响知之甚少。我们监测了树燕的繁殖活动（双色速染) 分布在加拿大魁北克省南部农业集约化梯度上的 40 个农场，以评估其饮食中农药的存在，并量化这些化合物在 2013 年至 2018 年期间对其生殖性能的暴露影响。我们首先评估了 54在 2,081 种由父母提供给雏鸟的食物丸剂（昆虫）中的杀虫剂中发现的活性剂（或衍生物），并记录了它们在我们研究区域内的空间分布。其次，我们评估了通过食物接触农药的影响（特定年份检测到的活性剂数量和特定农场受污染的药丸数量，同时控制采样工作）对离合器大小以及孵化和羽化成功以及雏鸟质量的影响初出茅庐时。杀虫剂在我们的研究系统中无处不在，近一半 (46%) 的食物丸被至少一种活性剂污染。然而，我们发现农药对食物污染的指标与树燕繁殖性能之间没有关系。需要更多的研究来更好地了解杀虫剂在农田鸟类和空中食虫动物数量减少中的假定作用，因为杀虫剂的潜在亚致死效应可以延续到生命后期并影响健康。