Montana Angler Fly Fishing’s Jimmy Armijo-Grover explains the ins and outs of fishing the March Brown mayfly hatch. The Western March Brown is one of the first mayflies to hatch on rivers in Southwest Montana and signals the beginning of the dry fly season for many anglers.
I was fishing European March Browns on a few western British rainfed (freestone) rivers this March and April with occasional marked success. One generic British March Brown pattern (and other lighter hued epherids) pattern is worth considering – The Jingler. Here is a video of a Brit with a very London – South East English accent tying one. Vary the sizes, materials colo(u)rs and how much material you dress the hook with, and you have a rough and ready but highly effective dry fly for all seasons wherever you may fish. Maybe add a little CDC, too, if you want a higher floater…. Soft hackle wet fly and beadhead versions also work well. Don’t overdress the pattern, though – tie its as sparse as you can “get away with”.
https://youtu.be/YqC4ydqIPJs