Sat 26-Jan-13 04:44 PM | edited Sat 26-Jan-13 04:45 PM by Lunastar
What species of birds will you be photographing? If it's larger birds like raptors, herons, etc the 300/4 w/14TC will be excellent. However, it's a bit slow for small fast birds like teal or terns. I'm not sure how quickly the Sigma 150-500 focuses but I'd opt for that as you are using a full frame body.