Birding lens. (1 Viewer)

Hello, I'm a 15 year old photographer from Bellevue, Washington, I am a landscape and street photographer, but in the past when I had a Canon system I used to go birding. I miss it and I'm just about to buy myself my first good telephoto lens. I really love the nikon 600mm f5.6 (manual focus). I know it's not an ideal lens for birds in flight, but I have heard that it produces amazing images that are almost as good as the vr version worth 6x+ the price. Unfortunately at my age I cannot afford an auto focusing version. I shoot using a d800, and would love to hear your opinion on what lens I should get. I did consider a 300mm f2.8 mf as well which I could use the modified nikon tc-16a with which would make the lens semi-af. The only problem is the reach... i also considered the nikon 200-500 and the sigma 150-600 and have heard that the images are pretty soft and lack contrast at their maximum focal lengths. Anyways, if anyone could give me any feedback or recommendations I would greatly appreciate it. Btw my budget is around 1.5k.
Thank you so much for your time,
Youri Babakoff.

I actually think the Sigma 150-600 Contemporary or the Nikon 200-500 are your best bets on a D800 with that budget. The Sigma would be my preference, but they're both very sharp. See my comments and comparison shots from this post:

http://www.birdforum.net/showpost.php?p=3374693&postcount=77

I'll add that I think they're optically better than the old MF Nikon primes, and much easier to use. I used to shoot with a manual focus 400mm f/3.5, and also used it with a TC-16A for semi-AF as you noted. It was pretty good as a bare MF lens, but lost a lot of image quality with the TC-16A. I sold it long before I got a chance to compare it to the Sigma 150-600, but the Sigma is a much sharper lens.

Also, many of the recent photos in my Flickr photostream (link in my profile) were taken using the 150-600mm Contemporary and with the D810 or D5500. I also have some shots with my 500mm f/4D AF-S II there for comparison; that lens is slightly sharper, and has slightly faster focusing speed, but the difference is very small.