Gandalf tells the Hobbits that the Nazgul's horses are bred in Mordor,
espeicially to serve Mordor. The originals may have been kidnapped, but all 9
are riding faithful (or less) beasts who not only are unafraid of them, but
serve them willingly.
And I don't recall the Nazgul scaring anyone but Men and Elves. I don't
remember seeing birds flee from him, or animal stampedes etcetc. The fear is an
active weapon for the Nazgul, not an 'aura' they use. Heck, Farmer Maggott
threatened to sick his dogs on the
Riders!
There is but one task remaining in Arda-we,the Dragons of Valinor will make it happen.
Lone resident of the Republic of Gondor
PO-TA-TOE-S not PO -TAH-TOE-S!