This, the stretcher of the cubital quills, is a very interesting muscle.
The last dozen vertebrae each carry a pair of well-developed typical quills.
These feathers are highly valued because they do not have quills.
Good sources for peacock quills are bird sanctuaries, zoos, tackle shops, or craft centers.
Stick floats, Avons and crow quills need to be dusted down and even bodied wagglers too.