Gil;
I only know what the lady at the Fly shop told me. She had a limited supply of original pattern flies on hand plus modern work around's which used a Yellow dyed Grizzly hackle. I bought one of her originals just for a keepsake. Didn't fish it as didn't want to chance losing it.

To the best of my knowledge the Yellowhammer is not on the endangered list. Under TN rules any species not having a specified open season is off limits.

Yes, they are of the Woodpecker family, I would suppose that's where the name Hammer comes from. Until the Coons put me out of business I kept out bird feeders & watched the birds a lot here n my backyard, next to a wooded hillside. Yellowhammers came around very frequently.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra