Denise, an additional suggestion that I don't think I have seen yet in the replies is to pay attention to what is behind your subject. Even if you get a very OOF background, it is still important what is behind the subject as far as distraction and contrast. By changing your position to you subject with a telephoto lens, you quickly change what is behind it (use crouching/standing or moving locations). Try to find an even background that is darker than the subject. Late in the day the diffuse warm light will light a bird well, but look for something behind it that is somewhat evenly toned and perhaps in shadow, or just less bright by a stop or two. This will make the subject pop! Of course for birds and the like you can spook them by moving a lot, so try and plan ahead of time where the subject will be (in my yard when the hummers are out, there are a few branches that they really like, for some reason). So get to that place and angle where your anticipate the subject to be and watch the background! Last year I sat on the top of a ladder for an hour feeling silly shooting birds that I could predict where they would be. Some of your pictures may not have the best background or have something distracting because you are shooting up at the subject. Consider climbing up a ladder!