Data from: High atmospheric temperatures and ‘ambient incubation’ drive embryonic development and lead to earlier hatching in a passerine bird

Tropical and subtropical species typically experience relatively high atmospheric temperatures during reproduction, and are subject to climate-related challenges that are largely unexplored, relative to more extensive work conducted in temperate regions. We studied the effects of high atmospheric and nest temperatures during reproduction in the zebra finch. We characterized the temperature within nests in a subtropical population of this species in relation to atmospheric temperature. Temperatures within nests frequently exceeded the level at which embryo’s develop optimally, even in the absence of parental incubation. We experimentally manipulated internal nest temperature to demonstrate that an average difference of 6°C in the nest temperature during the laying period reduced hatching time by an average of 3% of the total incubation time, owing to ‘ambient incubation’. Given the avian constraint of laying a single egg per day, the first eggs of a clutch are subject to prolonged effects of nest temperature relative to later laid eggs, potentially increasing hatching asynchrony. While birds may ameliorate the negative effects of ambient incubation on embryonic development by varying the location and design of their nests, high atmospheric temperatures are likely to constitute an important selective force on avian reproductive behaviour and physiology in subtropical and tropical regions, particularly in the light of predicted climate change that in many areas is leading to a higher frequency of hot days during the periods when birds breed.

相较于温带地区已开展的大量相关研究，热带与亚热带物种在繁殖期间通常会遭遇较高的大气温度，且面临诸多尚未得到充分探索的气候相关挑战。本研究以斑胸草雀（zebra finch）为研究对象，探究了繁殖期内高大气温度与巢温对其的影响。我们针对该物种的一个亚热带种群，对巢内温度与大气温度的关联特征进行了表征分析。结果显示，即便亲鸟未进行孵卵，巢内温度也时常超出胚胎发育的最优温度阈值。本研究通过实验操控巢内温度，证实产蛋阶段巢温平均相差6℃时，受"环境孵育"效应影响，雏鸟孵化时间平均会缩短总孵化时长的3%。由于鸟类每日仅能产下一枚卵的生理限制，同窝卵中先产出的个体相较于后续产出的个体，会受到更持久的巢温影响，这可能会加剧孵化异步性。尽管鸟类可通过调整巢的位置与结构，缓解环境孵育对胚胎发育的负面影响，但在亚热带与热带地区，高大气温度仍可能对鸟类的繁殖行为与生理机能构成重要的选择压力；尤其是在诸多地区的气候变化预测显示，鸟类繁殖期内高温天数愈发频繁的背景下，这一效应更为显著。