Data from: Supplemental food alters nest defence and incubation behaviour of an open-nesting wetland songbird

Climate-driven increases in spring temperatures are expected to result in higher prey availability earlier in the breeding season for insectivorous birds breeding in wetland habitats. Predation during the incubation phase is a major cause of nesting failure in open-nesting altricial birds such as the Eurasian reed warbler. The nest predation rate in this species has recently been shown to be substantially reduced under conditions of experimentally elevated invertebrate prey availability. Food availability near the nest may be an important determinant of adult incubation and nest defence behaviours during the incubation period. We used two experimental studies to compare incubation behaviour and nest defence in food-supplemented and unsupplemented adult Eurasian reed warblers during the incubation phase. In the first study we measured nest defence behavioural responses to a taxidermic mount of a native predator (a Stoat, Mustela erminea). In the second study we used temperature loggers installed in nests to measure breaks in incubation as a measure of nest vulnerability. Food-supplemented birds responded aggressively to the presence of a predator more quickly than those in the unsupplemented group, suggesting they are closer to their nest and can more quickly detect a predator in the vicinity. Food-supplemented birds also had shorter breaks in incubation (both in terms of maximum and mean off-bout durations), presumably because they were foraging for shorter periods or over shorter distances from the nest. This study therefore identifies the behavioural mechanisms by which changes in food availability may lead to changes in nest survival and thus breeding productivity, in open-nesting insectivorous birds.

气候变暖驱动的春季气温上升，预计将使湿地栖息地繁殖的食虫鸟类在繁殖季早期获得更多的猎物资源。对于欧亚苇莺（Eurasian reed warbler）这类开放式筑巢的晚成鸟而言，孵化期的捕食行为是导致筑巢失败的主要原因。近期研究表明，在实验提升无脊椎猎物可获得性的条件下，该物种的巢捕食率会显著降低。巢区附近的食物可获得性，可能是决定孵化期亲鸟孵化行为与巢防御行为的重要因素。本研究通过两项实验，对比了孵化期食物补给组与无补给组的成年欧亚苇莺的孵化行为与巢防御行为。第一项实验中，我们测量了亲鸟对本土捕食者——白鼬（Mustela erminea）剥制标本的巢防御行为响应。第二项实验中，我们在巢内安装温度记录仪，通过监测孵化中断时长来评估巢的脆弱性。食物补给组的亲鸟对捕食者出现的攻击性响应速度快于无补给组，这表明补给组亲鸟离巢更近，能够更快察觉周边的捕食者。此外，食物补给组亲鸟的孵化中断时长（包括最长单次离巢时长与平均离巢时长）更短，这可能是因为它们的觅食时长更短，或是觅食地点离巢穴的距离更近。因此，本研究阐明了食物可获得性变化如何通过相关行为机制，影响开放式筑巢食虫鸟类的巢存活率乃至繁殖生产力。