As we experienced the first time we visited Monteverde in March, 2004, the hummingbirds were active, beautiful and diverse. But, also typical for Monteverde, the conditions were dark and wet. I really don't like relying on flash so much, but there was really no choice here (or quite frequently in many Costa Rica locations). To avoid having the background too dark, I had to bump up the ISO, and keep the aperture relatively wide open. I also generally prefer shutter speeds in teh 1/250 to 1/320 range - quick enough to freeze motion in the head, but slow enough to give a little blur to the wings for a more 'dynamic' feel.