Hi,
I’ve not used them. In fact, I’ve not seen them! Can you post a photo of a few examples? Duck breast feathers can be used as “soft wings”, such as they are used in some of the old series such as the “Mallard” and “Teal” series. The Mallard and Claret is still a fairly popular change of light pattern (tail of golden pheasant tippets, body claret seals fur/wool/cheneil, rib gold tinsel or wire, wing bronze mallard, folded, hackle claret or black hackle feather). The others have gone out of fashion, but still catch fish. Things like a Mallard and red, mallard and yellow, etc, were basically the same but changed the body colour, and the hackle might change to brown, or furnace or ginger, whatever gives a nice colour ballance with the body. The wing was just bronze mallard fibres tied in as a wing. Because these feathers aren’t stiff like quill wings, the fibres tend to “break apart” so even if you take the time to tie them in like quill wing, the prettiness is lost pretty much as soon as they touch water and start catching fish. The teal series was much the same idea, only teal breast feathers were used. Of that, the teal, blue, and silver is probably the only one of any real remaining popularity; teal and green, teal and yellow, teal and blue, etc have all tended to be relegated to the history books. Worth digging them out though, as they still will catch fish.
Anyway, I would think you could do a series of flies using your green teal feathers, similar to the above series. There were also quill wing series named by similar convention (body colour and the winging material, such as the grouse and xxx, or the woodcock and xxx, etc).
I for one would be interested in seeing how they turn out, perhaps with some good examples of the “raw feather” beside a collection of different patterns? Say, green teal and silver, green teal and green, green teal and red, and as many as you can stand. Tied in size 10, you might find they are quite a useful series to carry with you to the water.
-Jeff