"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，因为它们可以通过确定何时开始孵化来控制它们的蛋的孵化间隔。然而，许多禽类父母选择了一种孵化策略，导致它们的鸡蛋异步孵化，这往往会导致年幼的雏鸟死亡。研究人员很少考虑气温如何影响孵化前鸡蛋的存活率(鸡蛋存活率假说)。卵不会在24摄氏度以下发育，必须由父母升温到36摄氏度才能确保正常发育。胚胎的异常发育导致死亡是由于鸡蛋长时间暴露在中温(27摄氏度-35摄氏度)中造成的。这项为期3年的研究采用波多黎各一座热带山区斜坡上的自然气候梯度，以珍珠鸡(Margaropfuscatus)的卵来检验鸡蛋存活率假说。珍珠鸡是一种在整个山脉的洞穴(和巢箱)中筑巢的物种。PI将在山上上下移动未孵化的蛋，使它们暴露在不同的温度条件下，并测量它们随后的孵化成功。PI还会将打蛋器放入孵化器中，使它们暴露在受控的温度变化中，这些温度变化与山上的温度变化平行。最后，PI将使用摄像机和温度记录器来检查Thrashers是否会在这个梯度上改变孵化开始时间。这将是第一次对影响鸟蛋孵化成功的因素进行研究，通过实验将鸟蛋暴露在一组关键的温度下，使用自然加热制度。未孵化的蛋孵化成功率的下降可能意味着理解为什么热带鸟类比温带鸟类下的蛋更少，以及它们的蛋在全球变暖中孵化成功可能会发生什么。

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.