When you're using a speedlight to capture or freeze something like this, you're not concerned with the shutter speed to do the freezing for you. The shutter will become about capturing ambient light. So you will be able to use something a lot slower than you're trying to use now. You'll never freeze motion without using a strobe. Not even close unfortunately, even with the fastest SLR.

You can set up your camera so that a reasonable shutter speed slow enough that it can sync with your flash. And a small enough aperture and low enough ambient light to produce an image that would not show the details of the hummingbird you want to freeze without the strobe. Next you just need to set the strobe (or multiple) up to provide enough light to produce the image you want. Perhaps the hummingbird isolated, perhaps trying to mimic natural light (will require at least two strobes, one for fill and the key).

The strobe will paint the image while your shutter is open. The hummingbird will be frozen if the strobe is the only thing (or predominant thing) lighting it.

I think you can get all the info you need here:
http://www.rpphoto.com/howto/hummer/humguide1.asp