Those are nice shots and with the 400/f2.8 + TC-20eIII making it 800mm, you've got it pretty sharp as is. That might be an option for me. It would give me a better range choice by using different TC's and even without at 400mm. Going out to the Nikon 600mm would give me a big gap in focal length and I don't think I'd want to purchase both the 600 and the 200-400 zoom. Thanks for your response.