CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France.
CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France.
J Therm Biol. 2022 Dec;110:103383. doi: 10.1016/j.jtherbio.2022.103383. Epub 2022 Oct 28.
Breeders evolved adaptive responses to rapid changes in ambient temperature. In birds, nests are expected to reduce egg cooling when the incubator is temporarily off the eggs. Here we present the results of two complementary laboratory experiments aiming at testing the association between egg cooling and the thickness of the nest under and surrounding the eggs in a non-domesticated avian model species (great tit, Parus major). To simulate incubation behaviour, we exposed nests with 4-egg clutches to a heat source until the eggs reached a normal incubation temperature (ca. 39 °C) and then recorded egg cooling 8 min after removal of the heat source, which corresponds to the time females generally leave eggs unattended during the incubation period. Eggs cooled more quickly when the nest layer under the eggs was thinner and when ambient temperature was cooler. We also show that the wall around the nest cup is important to buffer egg cooling. It is hypothesised that in bird nests, both the thickness of the material under the eggs, and the wall surrounding the nest cup interact to maintain a heat envelope around the eggs for the time the incubating parent is foraging. This could explain why the thickness of the nest base and wall are adjusted to the ambient temperature the birds experience during the nest building phase, to anticipate the thermal conditions during incubation and preserve egg viability.
饲养者进化出了适应环境温度快速变化的反应。在鸟类中，当孵化器暂时离开卵时，鸟巢有望减少卵的冷却。在这里，我们介绍了两项互补的实验室实验的结果，这些实验旨在测试非驯化鸟类模型物种（大山雀，Parus major）中卵冷却与卵下和周围巢厚度之间的关联。为了模拟孵化行为，我们将带有 4 个卵的鸟巢暴露在热源下，直到卵达到正常孵化温度（约 39°C），然后在热源移除 8 分钟后记录卵冷却情况，这对应于雌性在孵化期间通常离开卵无人看管的时间。当卵下的巢层较薄且环境温度较低时，卵冷却得更快。我们还表明，巢杯周围的壁对于缓冲卵冷却很重要。据推测，在鸟类的巢中，卵下材料的厚度以及巢杯周围的壁相互作用，以在孵育的亲代觅食时保持卵周围的热包络。这可以解释为什么巢的基部和壁的厚度会根据鸟类在筑巢阶段所经历的环境温度进行调整，以预测孵化期间的热条件并保持卵的活力。
