Data from: Plasticity in incubation behavior and shading by king rails (Rallus elegans) in response to temperature

King rails experience a wide range of temperatures during the course of the breeding season throughout their rapidly contracting geographic range. Incubating parent birds are adapted to keep their eggs within a temperature range appropriate for embryo development, but king rail clutches are at risk of exceeding lethal temperatures in the latter half of the nesting season. We investigated whether behavioral plasticity during incubation enables parents to maintain clutch temperature within tolerable limits for embryo development. Video revealed that king rail parents interrupted incubation to stand above and shade their eggs. We tested the hypothesis that the onset of shading was a direct response to ambient temperature (adaptive plasticity). We monitored clutch temperature directly by experimentally adding into clutches a model egg embedded with a programmable iButton. We measured ambient temperature at the nest site simultaneously. Parents spent proportionately more time shading and less time incubating their eggs at higher ambient temperatures. Shading may primarily function in cooling the parent. The frequency and duration of shading bouts were significantly greater at higher ambient temperatures. Parents also took more frequent but shorter recesses in hotter conditions. Diurnal recesses exposed eggs to direct sunlight, and the highest clutch temperatures were recorded under these conditions. Complete hatching failure in at least one nest was attributable to high clutch temperature for an extended period. Because mean ambient temperature increases throughout the breeding season, we investigated seasonal patterns in onset of incubation and its effect on hatching rate. Later in the season, parents tended to initiate incubation earlier, and hatching asynchrony increased significantly. Together these results suggest that breeding king rails may be constrained in their ability to cope with sustained high temperatures should seasonal averages continue to rise as predicted.王秧鸡（King rail）在其快速收缩的地理分布范围内，繁殖季全程会经历大幅温度波动。育雏亲鸟适应性地将卵维持在适合胚胎发育的温度区间内，但王秧鸡的卵团在筑巢季后半段存在超过致死温度的风险。本研究旨在探究育雏期间的行为可塑性是否可帮助亲鸟将卵团温度维持在胚胎发育可耐受的范围内。视频观测显示，王秧鸡亲鸟会中断育雏行为，站立在卵团上方为卵遮荫。我们检验了“遮荫行为的启动是对环境温度的直接响应（适应性可塑性）”这一假说。我们通过向卵团中植入一枚内置可编程iButton（programmable iButton）的模拟卵，直接监测卵团温度，并同时记录巢位处的环境温度。结果显示，随着环境温度升高，亲鸟用于遮荫的时间占比增加，而育雏时间占比相应减少。遮荫行为的主要功能可能是为亲鸟降温。随着环境温度升高，遮荫频次与单次遮荫时长均显著增加。在温度较高的环境中，亲鸟的离巢休憩频次更高，但单次休憩时长更短。日间离巢休憩会使卵团暴露于直射日光之下，此时记录到的卵团温度达到峰值。至少有一个巢出现了完全孵化失败，该失败可归因于卵团长时间处于高温环境。由于整个繁殖季的平均环境温度呈上升趋势，我们探究了育雏启动的季节模式及其对孵化率的影响。繁殖季越靠后，亲鸟往往会更早启动育雏，且孵化不同步性显著加剧。综合上述结果可见，若季节性平均气温如预测般持续攀升，繁殖期王秧鸡应对持续高温的能力或受到限制。