Département de biologie, Université de Sherbrooke, Sherbrooke, Québec, Canada.
Ecol Appl. 2022 Oct;32(7):e2645. doi: 10.1002/eap.2645. Epub 2022 Jun 13.
Climate change predicts the increased frequency, duration, and intensity of inclement weather periods such as unseasonably low temperatures (i.e., cold snaps) and prolonged precipitation. Many migratory species have advanced the phenology of important life history stages and, as a result, are likely to be exposed to these periods of inclement spring weather more often, therefore risking reduced fitness and population growth. For declining avian species, including aerial insectivores, anthropogenic landscape changes such as agricultural intensification are another driver of population declines. These landscape changes may affect the foraging ability of food provisioning parents and reduce the survival of nestlings exposed to inclement weather through, for example, pesticide exposure impairing thermoregulation and punctual anorexia. Breeding in agro-intensive landscapes may therefore exacerbate the negative effects of inclement weather under climate change. We observed that a significant reduction in the availability of insect prey occurred when daily maximum temperatures fell below 18.3°C, and thereby defined any day when the maximum temperature fell below this value as a day witnessing a cold snap. We then combined daily information on the occurrence of cold snaps and measures of precipitation to assess their impact on the fledging success of Tree Swallows (Tachycineta bicolor) occupying a nest box system placed across a gradient of agricultural intensification. Estimated fledging success of this declining aerial insectivore was 36.2% lower for broods experiencing 4 cold-snap days during the 12 days post-hatching period versus broods experiencing none, and this relationship was worsened when facing more precipitation. We further found that the overall negative effects of a brood experiencing periods of inclement weather was exacerbated in more agro-intensive landscapes. Our results indicate that two of the primary hypothesized drivers of many avian population declines may interact to further increase the rate of declines in certain landscape contexts.
气候变化预计会增加恶劣天气期（如不合时宜的低温期，即寒流）的频率、持续时间和强度，以及延长降水时间。许多迁徙物种已经提前了重要生命史阶段的物候期，因此更有可能经常暴露在这些恶劣的春季天气中，从而降低它们的适应能力和种群增长率。对于包括食虫鸟类在内的濒危鸟类物种来说，人为的景观变化，如农业集约化，是导致种群数量下降的另一个驱动因素。这些景观变化可能会影响提供食物的亲鸟的觅食能力，并降低暴露在恶劣天气下的雏鸟的存活率，例如，杀虫剂暴露会损害体温调节和定时厌食症。因此，在农业集约化景观中繁殖可能会加剧气候变化下恶劣天气的负面影响。我们观察到，当每日最高温度降至 18.3°C 以下时，昆虫猎物的供应显著减少，因此将每日最高温度降至该值以下的任何一天定义为寒流日。然后，我们结合每日寒流发生的信息和降水测量值，评估它们对在农业集约化梯度上放置的巢箱系统中繁殖的树燕（Tachycineta bicolor）的出飞成功率的影响。在孵化后 12 天内经历 4 个寒流日的雏鸟的出飞成功率比没有经历寒流日的雏鸟低 36.2%，而当面临更多降水时，这种关系会恶化。我们进一步发现，在农业集约化程度更高的景观中，一个经历恶劣天气期的巢窝的整体负面影响会加剧。我们的研究结果表明，许多鸟类种群下降的两个主要假设驱动因素可能会相互作用，在某些景观背景下进一步增加下降速度。
