The peacock spreads its tail feathers. 没有一点中文的诗意化吧？ 这就是语言和文化的差别。

孔雀开屏其实只涉及到尾羽，当然尾羽不止一根， 所以是tail feathers。

spread 的用法如下。

outspread 虽然可作动词用，倒是不常见，记得更多的时候用作形容词， 如 its outspread wings。

----------------- spread v., spread, spread·ing, spreads. v.tr. To open to a fuller extent or width; stretch: spread out the tablecloth; a bird spreading its wings.（出处：The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company.）。