"Does Egg Viability Constrain the Onset of Incubation in Birds? An Experimental Analysis using a Tropical Climate Gradient"

鸟类在脊椎动物中是独一无二的，因为它们可以通过决定何时开始孵化来控制它们的蛋的孵化间隔。 然而，许多鸟类父母选择孵化策略，导致他们的鸡蛋孵化异步，这往往导致年幼的小鸡死亡。 研究人员很少考虑空气温度如何影响鸡蛋在孵化前的存活（鸡蛋存活力假设）。 鸡蛋不会在24摄氏度以下发育，必须由父母加热到36度，以确保正常发育。 胚胎的异常发育导致死亡是由于卵长时间暴露在中等温度（27摄氏度-35摄氏度）下造成的。这项为期3年的研究利用沿着波多黎各一座热带山脉的斜坡的自然气候梯度来测试卵的活力假设。 PI将把未孵化的鸡蛋在山上和山下移动，使它们暴露在不同的温度下，并测量它们随后的孵化成功率。 PI还将把画眉蛋放在孵化器中，使它们暴露在受控的温度变化中，这种温度变化与沿着山脉的温度变化平行。 最后，PI将使用摄像机和温度记录仪来检查脱粒机是否会在此梯度上改变孵化的开始。 这将是第一项研究，通过实验性地将鸟蛋暴露在使用自然热制度的一组临界温度下，来研究影响鸟蛋孵化成功的因素。 未孵化的蛋孵化成功率的下降可能会对理解为什么热带鸟类比温带鸟类产的蛋少以及全球变暖可能会对它们的蛋孵化成功率产生影响产生影响。

Birds are unique among vertebrates because they can control the hatching intervals of their eggs by determining when to start incubating them. However, many avian parents choose an incubation strategy that causes their eggs to hatch asynchronously, which often leads to the death of younger chicks. Researchers have rarely considered how air temperature affects the survival of eggs before they are incubated (the Egg Viability Hypothesis). Eggs do not develop below 24 degrees C and must be warmed by a parent to 36 degrees to ensure proper development. Abnormal development of embryos leading to death is caused by prolonged exposure of eggs to intermediate temperatures (27 degrees-35 degreesC).This 3-year study employs a natural climate gradient along the slope of a tropical mountain in Puerto Rico to test the Egg Viability Hypothesis using eggs of the Pearly-eyed Thrasher (Margarops fuscatus), a species that nests in cavities (and nest boxes) throughout the mountain. The PI will move unincubated eggs up and down the mountain to expose them to different temperature regimes, and measure their subsequent hatching success. The PI will also place thrasher eggs in incubators to expose them to controlled changes in temperature that parallel temperature changes along the mountain. Finally, the PI will use video cameras and temperature recorders to examine whether thrashers vary the onset of incubation across this gradient. This will be the first study to examine the factors that affect the hatching success of bird eggs by experimentally exposing them to a critical set of temperatures using a natural thermal regime. A decline in the hatching success of unincubated eggs may have implications for understanding why tropical birds lay few eggs than temperate counterparts and what might happen to the hatching success of their eggs from global warming.