Only after stage 4 could additional feather variations evolve, including the many specializations we see at stage 5, such as the asymmetrical vane of a flight feather.
一旦演化到阶段4之后，其他各种不同的羽毛才能够演化出来，包括我们在阶段5看到的各种特化羽毛，例如飞羽的不对称羽片。
A tiny feathered "thumb," the alula, improves flight control. The protruding shaft on the first wing feather makes a loud, rustling sound—adding acoustics to the visual display.
微小的拇翼改善了对飞行的控制能力，第一翼羽上的凸出轴结构会发出沙沙的响声——在保持视觉效果的同时还增添了声学效果。
Wing feather with copper-containing pigment, flight and display, Courtesy Peter Mullen, Ph.D.
带有铜类色素的翅羽，飞行和展示用，彼得·穆伦博士惠赠
Wing covert feather, flight, Institute of Zoology and Zoological Museum, University of Hamburg.
翅膀隐羽，飞行用，汉堡大学动物学会和动物博物馆。
Wing feather with copper-containing pigment, flight and display, Courtesy Peter Mullen, Ph. D.
带有铜类色素的翅羽，飞行和展示用，彼得·穆伦博士惠赠。
A tiny feathered "thumb," the alula, improves flight control. The protruding shaft on the first wing feather makes a loud, rustling sound-adding acoustics to the visual display.
微小的拇翼改善了对飞行的控制能力，第一翼羽上的凸出轴结构会发出沙沙的响声——在保持视觉效果的同时还增添了声学效果。
Thee flight of the shuttlecock, a missile of cork and goose feather that players volley across the net, has been recorded at speeds of 260 kilometres per hour.
羽毛球由软木和鹅毛制成，飞行的最高时速可达260公里。选手在球落地前要将其接起并打过网。
Thee flight of the shuttlecock, a missile of cork and goose feather that players volley across the net, has been recorded at speeds of 260 kilometres per hour.
羽毛球由软木和鹅毛制成，飞行的最高时速可达260公里。选手在球落地前要将其接起并打过网。
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