I'm pretty new to DSLRs. I recently bought the Canon T1i & have 2 lenses (1: Canon EF 100mm f/2.8 Macro USM, 2: Canon EF 50mm f/1.8 II). I'm thinking the next lens should be a telephoto at least 200mm, but I just can't decide on which lens. For this next lens, I want something to take pictures of birds & animals outdoors. I keep getting told to buy primes lenses, but I feel like I want more versatility in a lens. I'm an amateur photographer so I think another prime isn't necessary. The only problem with the zoom lenses is that they seem really heavy but I'm willing to deal with the weight for the right lens. I probably want to keep the price under $600. Advice?