Peacock
Your source for flyfishing and flycraft resources since 1975.
As far as I'm concerned, the Peacock feather is simply 'Magic!' It's irridescence makes it irresistable to many fish and is used in a variety of patterns.
I couldn't imagine a fly tying desk that didn't have an ample supply of peacock 'herl.' These are the long thin fibers which stick out from the stem of the tail feather and also surround the eye. You can see it around the eye in the photo on the left. On the right is 'strung' herl, which is the most common way to buy it. It has already been stripped off the stem and then bound for easy access and less mess.
Regular herl is usually around 5" long, but you can also find longer herl, 10-14" long (which we sell, of course). My best advice is to make sure you always have some around!
It's used as body material, collars, legs, wing sacks, and so on. Below is an extended body dragon that I recently tied using peacock herl for the entire body and tail.
There are many other useful feathers found on the peacock including the eyes (shown above), wing quills and swords, one of my personal favorites because of its extraordinary irridescence and luster.
Remember, the feathers from the peacock are absolute magic to a tyer and a fish. Give all the different peacock feathers try.