Today, thankfully, the practice of wearing wild bird's feathers is illegal. For example, the eagle and the albatross can soar for hours without flapping a wing. Extend your arms. One flap equals touching your legs, raising your arms high, then touching your legs again. Have someone time the ten seconds for you.
Feathers further serve as great displays, especially when courting.
In general, the male birds' feathers are much brighter and more colorful than the females'. Most parrots, perhaps the most beautiful of all the birds, have feathers that look the same in both the male and female. There is a theory that perhaps the parrots see each others feathers differently than humans do, so they can tell the difference easily.