There are times when the use of flash can be helpful and then again it can totally mess up an outdoor nature shot. 'Fill' is the keyword, as a primary source flash won't be pleasing.
There was a post here not too long ago about the actual effectiveness of distance outdoors even with a beamer and it is limited. Shoot without the beamer with your flash to see if you notice some additional contrast or shadow fill. The Beamer will help bring more light to the subject but perhaps not make it really reach much farther.
I have several images where I have used it and was very pleased, when used properly it goes un-noticed, that is the key to success IMO
personally, I think a flash is best used indoors, I suggest you learn to work with natural light .. work with good backgrounds, and the light at your back, be creative, learn to shoot the overcast light, etc... but most will disagree with me!!
I had the better beamer, used it ones on my wife and daughter, and its been in a box since ( 3 yrs ago!)
I’m a strong believer in the creative use of flash for nature photography. I agree that you have to make it subtle. The idea is to add some catch light to the eyes of your subject which helps bring them to life. You can also balance shadows yet don’t want to wipe them out. The flash can help lift the subject a tiny bit above the background to make it stand out and will help bring out the iridescence in some birds feathers.
One of my unusual approaches to fill flash is to shoot with the sun behind my subject as this creates rim light. Then use the flash to light up the subject. Here is an example:
it all comes down to personal opinion, I always say, do what ever turns your crank.. and have fun... flash stuff is a creative tool that many nature photographers use very well... Tim and Morris have excellent examples here., superb in fact., it depends on what you like and enjoy...
You need a good flash, one that is built for the camera you are using., usually 400-500 dollars worth, and a better beamer does give your flash extended range.. you need to practice with the settings, and also, read some of the older posts on NIOM... here..
