For the uninitiated, strands of peacock tail feather can be used to tie up bodies on dry flies & nymphs. The strands of feather can also be stripped to make quill body flies as well. Many saltwater patterns call for peacock, too. A brief look at any collection of flies will show you just how many patterns use this material.
In fact, any pattern can be spruced up by adding some peacock - even those that don't call for it. Add a head of a few turns of peacock for a head on that nymph pattern you just tied up & the trout will like it even more. Add a thorax of peacock just behind the hackle on that wet fly - it makes the hackle stand away from the hook & adds a bit of attention-getting sparkle to the fly. Try winding it up the length of that caddis larva pattern, rib-style, to better imitate those free-living (non-case making) caddis that are in the drift. The possibilities of using peacock to enhance your fly patterns are limited only by your imagination.
Here are a few tips for tying flies with peacock:
1.) Tie in more than one strand - at least 2 on very small flies (#18 & up) & normally 3 strands (#10 - #16 hooks). This makes for a better, fuller body.
2.) Always tie the herl in at the tip ends. This is where the better fibers are, towards the tip.
3.) You can (but don't have to) stroke the herl before winding it around the hook so that the fibers stand away from the stem.
4.) Some folks make a "rope" of herl by twisting it around the wrapping thread before they wrap the peacock up the hook. This is supposed to make the fly stronger & it looks the same as if you didn't do this - so no loss of appearance.
5.) It's a good idea to make an under-body of the herl & thread before wrapping the herl up the hook. This helps to give the fly a nice flat, even shaped body. Some folks even apply a few dabs of instant glue to this under-body. Doing this will literally glue your peacock wraps in place on the hook, which will make for a very strong fly.
6.) If you're tying a peacock body on a fly that also calls for palmered hackle &/or ribbing of some kind, it's a good idea to wind the rib or hackle in the opposite direction that you wound the peacock. This helps to lock it in place & holds it down & together better when a fish tries to eat it.
The main drawback of peacock as a fly tying material is that it can be brittle & break easily, if you're not careful. After a good chomp or two from a fish, the peacock will become tattered or broken & thus ineffective. But these drawbacks do not outweigh the benefits of using peacock.
As a fly material it goes well with gold ribbing, brown hackle, mallard side feathers, & many different colors of dubbing & hair. There's a reason why fly anglers have been using peacock for all this time. Try enhancing some of your favorite fly patterns with it, dry or wet, & you'll see why so many patterns call for it's use.