It had asymmetric flight feathers not only on the forelimb, but on the hindlimb as well.
它已非对称飞羽不仅对前肢，但对后肢以及。
University of Washington scientists say it depends on how fast you can replace your flight feathers when you molt.
来自华盛顿大学的科学家们说，这取决于在换羽的时候，你更换飞行羽毛的速度。
Small birds molt once or twice a year, and they replace their 9 or 10 primary flight feathers a few at a time over the course of a few weeks.
小型鸟类一年进行一到两次换羽，在换羽期间，它们一次会替换掉9到10根左右的飞羽，而这个过程将持续几周时间。
So what if you want to fly? University of Washington scientists say it depends on how fast you can replace your flight feathers when you molt.
那么，你如果想飞，你的体重该保持在什么水平上呢？华盛顿大学的科学家们说，这取决于你在换羽期间更换飞羽的速度。
Small birds molt once or twice a year, and they replace their 9 or 10 primary flight feathers a few at a time over the course of a few weeks.
形体小的鸟儿一年脱羽一到两次。它们有9到10只主要用于飞行的羽毛，鸟儿们一次更换几只，在几周的时间内它们就可以完成更换。
As feathers became larger over time, flapping flight evolved and birds finally became fully air-borne.
随着时间的推移，羽毛变得越来越大，扑翼飞行逐渐发展，鸟类最终完全可以在空中飞行。
Larger feathers could have increased lift incrementally, until sustained flight was gradually achieved.
较大的羽毛可以逐渐增加升力，直到逐渐实现持续的飞行。
As we've discussed, birds are apparently descendants of dinosaurs and shared many commonalities with some dinosaur species, like feathers and maybe even flight and of course egg laid.
正如我们讨论过的，鸟类显然是恐龙的后代，与一些恐龙物种有许多共同之处，比如羽毛，甚至飞行，当然还有产卵。
Although birds use their feathers for flight, some of their feathers are for other purposes.
虽然鸟类用羽毛飞行，但有些鸟类的羽毛还有其他用途。
In short, the evolution of feathers would have happened along with the evolution of flight.
简而言之，羽毛的进化史是伴随着飞行的进化同时发生的。
If feathers did not evolve first for flight, what other advantage could they have provided the creatures that had them?
如果羽毛并不是为了飞行而进化的，那它们又能为宿主带来哪些益处呢？
By adding some feathers at the back, an arrow could be prevented from turning sideways during flight.
后来，人们在箭矢的尾部装上羽毛。这样一来，箭在飞行的过程中就不会偏离目标了。
If feathers did not evolve first for flight, what was their purpose?
如果羽毛进化的初衷并非是为了飞行，那么这种进化的意图何在？
narrow feathers and weak flight muscles suggest it was not a powerful flier.
狭窄的羽毛和柔软无力的飞翔肌暗示孔子鸟并非是个高超的飞行大师。
And of course they aid flight-but not always, as ostriches and penguins, which have feathers but do not fly, demonstrate.
当然，羽毛还能辅助飞行——但这也并非绝对，鸵鸟和企鹅虽然也拥有羽毛，但却不会飞行。
Feathers did, of course, eventually become an instrument of flight.
当然，羽毛最终进化成为飞翔的工具。
He added that, since these ancient feathers didn't aid flight, they likely served for purposes of animal communication, mating, and warmth.
他补充道，远古时期的羽毛并不用于飞翔，而是起到与其他动物沟通、求偶及取暖的作用。
Whatever the original purpose of feathers, they were probably around for millions of years before a single lineage of dinosaurs began to use them for flight.
不管羽毛进化的起初目的是什么，总之它们又经历了上千万年的时间才承载着某支恐龙谱系开始翱翔于蓝天。
It could be that dinosaurs with more primitive feathers used them for temperature regulation, camouflage and visual signaling, rather than flight.
拥有更为原始的羽毛的恐龙，当初可能将其用于调节身体温度、伪装和发出视觉信号，而非辅助飞行。
Many of the feathers seem to be small, brown and fluffy - probably for warmth rather than flight.
许多羽毛看上去是细小的褐色蓬松的茸毛，可能主要是用于保暖，而不是用于飞行。
This is the voice of the mysterious swan in the humid air flight wings beat against the wind the voices of feathers.
这神秘的声音就是天鹅在潮湿的空气中翅膀拍打羽毛逆风飞行的声音。
The males courted the females by means of nuptial flight, displaying nuptial feathers, feeding and courtship nesting.
求偶方式主要有婚飞、显示饰羽、求偶喂食和象征性营巢行为；
Her mate is grooming her as she sleeps, plucking off feathers that have loosened during her flight.
她的同伴在她睡觉时为她守候，为她梳理在飞行期间巳经松动的羽毛。
Upperwing has pale greyish-white primary bases and often pale rufous or yellowish-brown forewing, paler than dark grey flight-feathers.
翼上初级飞羽呈现灰白色，翼前缘经常为淡棕色或黄棕色，比飞羽的深灰色要浅。
Many of the feathers seem to be small, brown and fluffy - probably for warmth rather than flight.
许多羽毛看上去是细小的棕色的茸毛，可能主要是用于保暖，而不是飞翔。
Many of the feathers seem to be small, brown and fluffy - probably for warmth rather than flight.
许多羽毛看上去是细小的棕色的茸毛，可能主要是用于保暖，而不是飞翔。
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