Song birds are small so they're hard to shoot, but what harder is to get them in good light, good head angle, good eye contact, good pose, clear background and no distracting object in front of the bird in order to have a presentable image. I have no problem with shooting song birds with my bare 500 and the 40D. I definitely like to shoot song birds to diversify my portfolio, but what really keeps me from actually doing it is the lack of action.