It's the way to go for more than just hummingbirds - I've been setting up like this since Feb 2010 for all of my bird shots.
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This Downy Woodpecker is the latest with a 43" umbrella.
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You can use the ST-E2, that is how I started out, but you will quickly hit the wall of it's limitations outdoors. Your range will be restricted to about 30 feet or so, fine for the birds you are shooting but no good if you want to position a second flash to light that distant background.
Strong sunlight can kill your infrared signal - at times, shooting with the Canon system can be fickle at best and broken at worst when used outdoors.
The ST-E2, being infrared, requires line of sight between your camera and each flash. Such things as a photo blind and light modifiers like umbrellas can block the signal.
The ST-E2 is great for indoor settings where the signal can bounce around a room but for outdoor jobs a radio trigger is a much better option.
Given the close distance you can set your flash to your subject you will find that a better beamer is not necessary.