Fill flash? My First attempt !

I have long pondered on wheather to try or even learn how to succesfully use fill flash in my wildlife photography. I only want to fill in the shadows not be the main source of light. After plenty of research I decided to give it a go the next opportunity I thought it suited. So after a while searching I stumbled on a female Pheasant that didn't budge (she wasnt on a nest) I took a couple of shots not very good shots but just a snap shot then on quick review I noticed a huge shadow on the breast of the bird so I popped up my built in flash set it to +0 and fired off a shot. This Time I used my built in flash but in the future I will be usin Canon Speedlite 580X II with a diffuser. Natural light is ALWAYS best!

This is the image with Fill flash. More frame filling as a took a couple of steps forward. Now in this image I think the Back of the bird is maybe a little over exposed but much better than the other image below. The Breast and head of the bird has lost the extreme shadows, still there is shadowing but I think it's an improvement. If I set the flash at +1 or +1 1/3 then the the back of the bird would have been over exposed and the breast would have been fine although I could have pumped up apperture to f.8. But changing appertures when using flash comes with all sorts of problems.

This is the image without fill flash. As you can see not an appealing photograph by any means. But in my opinon the back of the bird is a little underexposed. Also as you can see the breast of the bird has extreme shadows along with the head. I have A lot to learn on this matter and will carry on reading and playing with it in the field. I will keep my blog up to date with this and hopefully in weeks and months to come I will notice a improvment. Not all photographers like to use flashes on wildlife or at all but in situtions it will hopefully prove a session saver! Ambient light is ofcourse always the best! I wont be using Fill flash in all my images just drastic shadows like this situation. Anybody's thoughts, questions or even advice are very welcome. Thanks :)