Originally posted by GeneV Of course you can use a flash. I've also snagged some nice shots in low light with my 55-300 and the pop up, or with my Metz 64AF and Better Beamer. I have even set up multiple flashes on tripods for catching birds in low light. You can make almost anything work, but if you are trying to travel light as the OP implied, heavily overcast days are not your friend with that lens plus converter.
Yes, no doubt - when f8 is a starting point, low light is tough. The good thing about the Rogue is that it weighs next to nothing, is cheap, and can get you photos you wouldn't otherwise get, provided the birds aren't too far away (<15m or say 50').
BTW, I've been looking at flashes myself, Gene, and I found your reviews of the Metz 64, Sigma 610 and Pentax 540 all very helpful.