We used allometric scaling to explain why the regular replacement of the primary flight feathers requires disproportionately more time for large birds. Primary growth rate scales to mass (M) as M 0.171, whereas the summed length of the primaries scales almost twice as fast (M 0.316). The ratio of length (mm) to rate (mm/day), which would be the time needed to replace all the primaries one by one, increases as the 0.14 power of mass (M 0.316/M 0.171 = M 0.145), illustrating why the time required to replace the primaries is so important to life history evolution in large birds. Smaller birds generally replace all their flight feathers annually, but larger birds that fly while renewing their primaries often extend the primary molt over two or more years. Most flying birds exhibit one of three fundamentally different modes of primary replacement, and the size distributions of birds associated with these replacement modes suggest that birds that replace their primaries in a single wave of molt cannot approach the size of the largest flying birds without first transitioning to a more complex mode of primary replacement. Finally, we propose two models that could account for the 1/6 power allometry between feather growth rate and body mass, both based on a length-to-surface relationship that transforms the linear, cylindrical growing region responsible for producing feather tissue into an essentially two-dimensional structure. These allometric relationships offer a general explanation for flight feather replacement requiring disproportionately more time for large birds.
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机译:我们使用异度缩放比例来解释为什么定期更换主要的飞行羽毛对于大型鸟类来说需要更多的时间。初级生长的比例缩放为质量(M),为M 0.171 sup>,而初级生长的总长度缩放几乎快两倍(M 0.316 sup>)。长度(mm)与速率(mm / day)的比率,即一一替换所有基色所需的时间,随质量的0.14幂而增加(M 0.316 sup> / M < (sup> 0.171 sup> = M 0.145 sup>),这说明了替换基色所需的时间为何对大型鸟类的生活史进化如此重要。较小的鸟类通常每年更换所有的飞行羽毛,但是在更新初生时飞行的较大的鸟类通常将初生蜕皮延长两年或更长时间。大多数飞鸟表现出三种基本不同的主要替换模式之一,并且与这些替换模式相关的鸟的大小分布表明,在一次蜕皮中替换其主要候鸟的鸟无法接近最大飞鸟的大小,而无需先过渡到更复杂的一次更换模式。最后,我们提出了两个模型,它们可以解释羽毛生长速率与体重之间的1/6幂异构关系,这两个模型都是基于长度与表面的关系,这种关系将负责生产羽毛组织的线性圆柱状生长区域转化为基本上是二维结构。这些异形关系为替换大羽鸟提供了一般解释,这需要大得多的时间。
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