Well, really it's the Pennant-winged Nightjar.
The young-uns are born with normal wings (this one was caught "in a state of exhaustion" and then revived and released, awwww.):
When they're adults "the males acquire a striking 9th primary feather during the breeding season. These pennants grow to greater lengths in successive years, up to twice the body length. They are dropped or broken off quickly upon completion of breeding." Source.
Some of course are, ahem, larger than others (it even looks smug, lol):
Heeeeeeey there ladies, lookin fine tonight.