Incubation length and hatching asynchrony are integral elements of the evolved reproductive strategies of birds. We examined intra- and interpopulation variation in both traits for Eastern Kingbird (Tyrannus tyrannus) populations from New York (NY), Kansas (KS), and Oregon (OR) and found that both incubation length and hatching asynchrony were not repeatable among females, after controlling for a repeatable trait, clutch size. Instead, incubation length and clutch size were influenced by ambient temperature and precipitation. Incubation length exhibited the same median (15 days) and range (13–17 days) at all sites. Model selection results indicated that incubation periods for the smallest and largest clutches were longer in NY than KS when rain was frequent throughout incubation, in replacement nests, and likely when ambient temperatures were low during egg-laying. Full hatching usually required 2 days (but up to 3), with synchronous hatching associated with small clutch sizes, short incubation periods, frequent rain during the egg-laying period, and low ambient temperatures during the first half of incubation. Nestling starvation was uncommon (5–9% of nestlings monitored) and not associated with greater hatching asynchrony. These results indicate that while clutch size, a repeatable female trait, contributed to variation in incubation length and hatching asynchrony in Eastern Kingbirds, weather was a greater source of variation, especially for incubation length.

中文翻译：

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东部王鸟孵化长度和孵化不同步的变化：天气使雌性影响黯然失色

孵化长度和孵化不同步性是鸟类进化繁殖策略的组成部分。我们检查了来自纽约 (NY)、堪萨斯州 (KS) 和俄勒冈州 (OR) 的东部帝王鸟 (Tyrannus tyrannus) 种群的种群内和种群间变异，发现孵化长度和孵化异步在雌性中均不可重复，在控制了可重复性状后，离合器尺寸。相反，孵化长度和离合器大小受环境温度和降水的影响。孵化时间在所有地点表现出相同的中位数（15 天）和范围（13-17 天）。模型选择结果表明，在整个孵化过程中经常下雨时，纽约最小和最大离合器的孵化期比堪萨斯州长，在替换巢穴中，并且可能在产卵期间环境温度较低时。完全孵化通常需要 2 天（但最多 3 天），同步孵化与小离合器尺寸、短孵化期、产卵期频繁下雨以及孵化前半期环境温度低有关。雏鸟饥饿并不常见（监测到 5-9% 的雏鸟），并且与更大的孵化不同步性无关。这些结果表明，虽然离合器大小（一种可重复的雌性特征）导致东部帝王鸟孵化长度和孵化不同步的变化，但天气是一个更大的变化来源，尤其是孵化长度。产卵期经常下雨，孵化前半段环境温度低。雏鸟饥饿并不常见（监测到 5-9% 的雏鸟），并且与更大的孵化不同步性无关。这些结果表明，虽然离合器大小（一种可重复的雌性特征）导致东部帝王鸟孵化长度和孵化不同步的变化，但天气是一个更大的变化来源，尤其是孵化长度。产卵期经常下雨，孵化前半段环境温度低。雏鸟饥饿并不常见（监测到 5-9% 的雏鸟），并且与更大的孵化不同步性无关。这些结果表明，虽然离合器大小（一种可重复的雌性特征）导致东部帝王鸟孵化长度和孵化不同步的变化，但天气是一个更大的变化来源，尤其是孵化长度。