I've never tried to photograph humming birds, and would likely just shoot a video of them and then frame grab the better shots out of the video, but if I was really trying to get still shots of them and needed to use flash, I would likely buy one of the long support bars designed to allow attaching several lights on cold shoes to the 1/4-20 attachment point on the bottom of the camera and either use sync cables or a wireless transmitter attached to the camera hot shoe to trigger them. For the background light, it is possible to mount a cold shoe to the bottom of these bars by reversing the 1/4-20 attachment bolt, thereby allowing a lower light source that would still follow the camera position. If shooting with the hummingbird relatively close to the camera you may have far too much light though (you may temporarily blind the poor bird) and I doubt that after the flash that you will ever get a second shot of the same bird. They are timid enough already.
Just suggesting a relatively cheap way of attaching several speedlites to your camera. There are small ball heads that could be used under the cold shoes if you wanted more positioning capability of the speedlites too. Again, I have never tried to photograph hummingbirds, but if I wanted to do this in low light conditions, I would likely put together speedlites in some sort of arrangement using one of these bars. Attaching a handle below the camera position would likely be a good idea too. The bolts that come with these brackets have female 1/4-20 inserts in their knobs to make attaching/stacking a handle or tripod to it easily.
Costa Rica is quite an experience. Get out and away from the cities and it's amazing, but I'm not sure it would be very safe at night.
Charley
