Wild duck CDC is just a different kind of feather when compared to those gathered from domestic birds. Once you try it, you are never going back! We cannot imagine ourselves tying dry flies or nymphs with anything else nowadays, it is just that much superior!
A 0.5-gram pack is usually enough to tie up at least a couple of dozen flies, and more if you are tying primarily small flies. A 1-gram pack is plentiful and meant for the tyer that spends a lot of time on the vise.