Hi there, I'm fairly new to photography and I'm currently on a college course to learn basic skills, we have been asked to create a portfolio of pictures that we really like. The pictures I find most appealing are that of wildlife, specifically birds, so this morning I got my equipment up together and headed down to the local nature reserve where I spotted 3 waders just accross the estuary. The lens I was using was a 70-300mm tamron 1:4-5.6 tele-macro, the idea was to zoom in as far as I can and then crop the picture down later, however, when I zoom in, the birds are not in focus at all, is there something that I'm not doing? Or is the lens that I'm using not adequate? Pls help!! 

