College of Agricultural Sciences and Natural Resources, Texas A&M University - Commerce, Commerce, Texas, United States of America.
PLoS One. 2019 Jul 10;14(7):e0219368. doi: 10.1371/journal.pone.0219368. eCollection 2019.
Temperature extremes alter development, growth, hatching, and survival of eggs of ground-nesting birds, particularly during pre-incubation (egg laying) when eggs are left unattended and exposed to the environment for days or weeks before parental incubation begins. The northern bobwhite quail is a ground-nesting bird whose eggs experience high temperatures (≥45° C) during pre-incubation. It is known that chronic high temperatures during pre-incubation alter development and reduce hatching and survival of bobwhite eggs, but it is not known if acute doses of high temperatures during pre-incubation have the same effect. In this study, the 12-d pre-incubation period was divided into thirds. Fresh bobwhite eggs were exposed to either a commercial holding temperature for all 12 d (serving as a control), or a high oscillating temperature regimen for 4 d (one third of pre-incubation) either in the early, middle, or late third of pre-incubation, with a low oscillating temperature regimen during the remaining 8 d. The timing of acute exposure to high oscillating temperatures significantly affected bobwhite development. Eggs exposed in the first 2/3 of pre-incubation developed twice as much as eggs exposed late in pre-incubation, even though all eggs received the same amount of heating degree-hours. Thus, a critical window of thermal susceptibility exists for developing northern bobwhites. Acute exposure to high oscillating temperatures resulted in reduced hatchling mass, hatching success, survival, and compromised hatching synchrony. Thus, acute hyperthermic nest temperatures during pre-incubation could result in the observed reductions in the percentage of juveniles in natural populations during hot and droughty years.
温度极端会改变地面筑巢鸟类的卵的发育、生长、孵化和存活，尤其是在孵卵前期（产卵期间），此时卵无人看管，在亲代孵卵开始前可能会暴露在环境中数天或数周。北美野鹌鹑是一种地面筑巢的鸟类，其卵在孵卵前期会经历高温（≥45°C）。已知孵卵前期的慢性高温会改变发育并降低鹌鹑卵的孵化率和存活率，但尚不清楚孵卵前期的急性高温剂量是否会产生相同的影响。在这项研究中，将 12 天的孵卵前期分为三分之一。新鲜的野鹌鹑卵要么暴露在整个 12 天的商业孵化温度下（作为对照），要么暴露在高温波动温度方案中 4 天（孵卵前期的三分之一），要么在孵卵前期的早期、中期或晚期，要么在剩余的 8 天中暴露在低温波动温度方案下。急性暴露于高温波动的时间显著影响了野鹌鹑的发育。在孵卵前期的前 2/3 时间内暴露的卵的发育程度是在孵卵后期暴露的卵的两倍，尽管所有卵接受的加热程度小时数相同。因此，对于发育中的北美野鹌鹑，存在一个关键的热敏感性窗口。急性暴露于高温波动会导致雏鸟体重减轻、孵化成功率降低、存活率降低以及孵化同步性受损。因此，在孵卵前期的急性高温巢温可能导致在炎热和干旱年份中观察到自然种群中幼体百分比的降低。
