Is this hummer the same one you had a problem with? If so, here's 2 suggestions:
1/ Dont set EC to +1. If that's what you did, the camera will set an exposure setting that yields a +1 exposure to the entire image. In Av or Tv modes with a flash, the camera sets the exposure to be exactly what it would be without a flash - the flash then provides fill light. So if you set EC to +1, the whole image - subject and background - will be overexposed by 1 stop. That is what is causing the overexposure, not the flash.
Look at the background - it is too bright compared what you described it to be. The exposure setting which causes the background to be lit so much is also what is causing the bird to be overexposed.
Start with EC set to 0 and FEC to -1. Alternatively, use EC of -0.5 to -1 and FEC of 0.
In this particular case, as you have a dark background, use EC of -1 and set FEC to 0 or -0.5. That should sort it out, or be close enough as a starting point.
2/ In general, if you are overexposing with the flash, try using a lower ISO. That will reduce the sensitivity of the sensor to the flash.. which effectively serves the same purpose as lowering flash power.
Vandit
