Getting the best out of rainforest birds with my oly kit?

Hi,

I am heading to Madagascar in October. I shoot with an olympus E-620 and the 50-200 with and without a 1.4 converter. The lens is really sharp and fast but the body is not so good in low light. I don't plan to invest more in a new system so want to try and get the most out of what I have. My main concern is shooting birds and lemurs in the rainforest of Andasibe and Ranomafana. Obviously I will look to use a tripod or monopod where this is feasible, but bearing in mind we'll be doing a lot of walking on steep trails etc, I want to keep the weight down as much as possble. Would you recommend taking a flash in these circumstances or are there any other hints and tips you have for me to get the best out of my kit in these circumstances?

All the best

Jo