Jane Westervelt's inquiring mind wanted to know:

"Is the correct term "juvenal" or "juvenile" or are they
both correct in different contexts? And if so, what are
the contexts? Whenever I see "juvenal" I end up wondering
if it's yet another typo, or if I've missed something."

And now here's the soi-disant authoritative answer:

If we are referring to the plumage of young birds, then either
"juvenal" or "juvenile" is a standard English adjective.

"Juvenal plumage" is the more stodgy of the two, which may
be why some folks like it.

You won't find the adjective "juvenal" at all in such a
standard desk dictionary as _Merriam-Webster's Collegiate
Dictionary, Tenth Edition_. You'll need to go the unabridged
to find it. The adjective "juvenal" seems to survive mostly
in writings of some ornithologists and birders. The noun
"juvenal, meaning youth, is archaic.

On the other hand, "juvenile" is still both a noun and an
adjective and is also appropriately applied to plumage.

And, yes, Juvenal, the first-century Roman poet and maker
of juvenalian satire, is remembered for asking, "Who will
guard the guards themselves?"

--cheers, Jim Lyles
Tacoma