Swiss Ornithological Institute, CH-6204 Sempach, Switzerland.
Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, Durban 4000, South Africa.
Proc Biol Sci. 2019 Sep 11;286(1910):20191537. doi: 10.1098/rspb.2019.1537. Epub 2019 Sep 4.
Equivocal knowledge of the phase-specific drivers of natal dispersal remains a major deficit in understanding causes and consequences of dispersal and thus, spatial dynamics within and between populations. We performed a field experiment combining partial cross-fostering of nestlings and nestling food supplementation in little owls (Athene noctua). This approach disentangled the effect of nestling origin from the effect of the rearing environment on dispersal behaviour, while simultaneously investigating the effect of food availability in the rearing environment. We radio-tracked fledglings to quantify the timing of pre-emigration forays and emigration, foray and transfer duration, and the dispersal distances. Dispersal characteristics of the pre-emigration phase were affected by the rearing environment rather than by the origin of nestlings. In food-poor habitats, supplemented individuals emigrated later than unsupplemented individuals. By contrast, transfer duration and distance were influenced by the birds' origin rather than by their rearing environment. We found no correlation between timing of emigration and transfer duration or distance. We conclude that food supply to the nestlings and other characteristics of the rearing environment modulate the timing of emigration, while innate traits associated with the nestling origin affect the transfer phases after emigration. The dispersal behaviours of juveniles prior and after emigration, therefore, were related to different determinants, and are suggested to form different life-history traits.
对生殖扩散特定阶段驱动因素的模棱两可的认识仍然是理解扩散原因和后果以及种群内和种群间空间动态的主要缺陷。我们进行了一项现场实验，结合了雏鸟的部分交叉抚育和雏鸟食物补充，以研究小猫头鹰（Athene noctua）的扩散行为。这种方法将巢雏的起源效应与饲养环境对扩散行为的影响分离开来，同时研究了饲养环境中食物供应的影响。我们使用无线电跟踪幼鸟来量化出飞前探索和迁移、探索和转移持续时间以及扩散距离。出飞前阶段的扩散特征受饲养环境的影响，而不是巢雏的起源。在食物匮乏的栖息地中，补充食物的个体比未补充食物的个体迁移晚。相比之下，转移持续时间和距离受鸟类起源的影响，而不受饲养环境的影响。我们没有发现迁移时间与转移持续时间或距离之间存在相关性。我们得出结论，巢雏的食物供应和饲养环境的其他特征调节了迁移的时间，而与巢雏起源相关的内在特征则影响了出飞后的转移阶段。因此，出飞前后幼鸟的扩散行为与不同的决定因素有关，并且可能形成不同的生活史特征。
