Definition of "rectrix" []

• One of the stiff main feathers of a bird's tail, used to control the direction of flight. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "_P.c. amoenissima_, and the black at the base of the inner webs of the outermost rectrix does not extend beyond the tip of the under tail coverts."
• "Representatives of _P.c. amoenissima_ have black at the base of the inner web of the outermost rectrix more extended, usually showing beyond the tip of the under tail coverts."
• "The outermost rectrix of No. 31633 is wholly white; the second rectrix is nearly as white."