Regarding cree hackle,

The reason you don't see it called for in modern fly dressing is because of it's scarcity. When tying patterns today like the Adams you would only need one cree hackle as opposed to one brown and one grizzly which is a pain in the a$$! A good cree neck is worth it's weight in gold if you tie alot of flies that today call for two different hackle feathers to recreate the look of one cree feather.

JA