CDC Emerger 

CDC or Ducks Bum is an absolutely fabulous fly tying material, boyant yet very supple, these feathers are just fantastic for tying flies. I know of no other natural material that combine the ability to float and yet remain delicate and very insect like, and they can be used in any situation from huge stillwaters to small streams, as well as that there is nothing so exciting a watching a feeding fish sip down your CDC fly and then simply raising your rod into a feeding fish, Fantastic.