Peter O'Toole has recommended some Nikon gear and all of his suggestions are top-notch product.
My feeling is that you are not quite prepared to spend that much money. It's a mighty leap from
what you use now to Mr. O'Toole's kit. The prices he quotes make me dizzy because a few thousand
bucks for me might as well be a few million, because I'm no closer to comprehending one figure than the other.
You do not need to spend that much to get decent pictures. A cropped sensor size is a given. Regardless of
the lens you ultimate decide upon you will need to crop in post. If your sensor is too small then cropping will
define noise you will not be pleased to see. It will also limit your useful ISO capabilities for the same reason.
A cropped sensor DSLR can be had for under a grand (after taxes). Newer entry-level DSLR cameras have 24 mega-pixel sensors.
Whether Canon or Nikon those newer sensors will allow you to crop a lot. I have a Canon T4i (18 megapixels) and I
can crop favourably. Indeed, I need to crop because I'm using a 70-200mm lens (f4) without IS. That lens sells for
maybe $800. So, a new camera with a new sensor is about $800.00 too.
That's not chicken feed, but it is a darn sight cheaper than Mr. O'Toole's wonderful gear. Canon also makes the old
400mm f5.6 prime lens w/o IS. I wish I had one. It is sharp as heck, but needs a fair amount of light at f5.6 and especially
without the benefit of IS to facilitate using lower shutter speeds. Still, the lens cost less than half of the Nikon 80-400mm f 5.6 with VR.
The light weight Canon that I'm using is easy to carry in the field, easy to deploy at short notice, sharp as a tack ... but no IS. I got mine used as a gift.
Indeed, my Canon T4i was also a gift, otherwise I wouldn't be shooting birds. I simply can't afford the gear that most birders would
consider a pre-requisite, but I have not let that stop me. Your best piece of kit is an alarm clock. It will get you up in time to get out
in time, to get to the site in time, to get the sightings to get the shot. With a cheaper, shorter lens you will need to get closer to your
subject. That can be done, but it means you need to try harder and use some ingenuity. Heck, that's half the fun!
Mirrorless cameras with electronic viewfinders are the immediate future, so take that into consideration too. Just don't spend a lot of money you
may not have. Build up to it gradually. Tamron and Sigma is not too expensive but these lenses are heavy, push-pull and slow (f6.3). The glass is good
but not great. A Canon 400mm f5.6 prime cropped to 600mm was sharper than a Tamron 150-600mm shooting full out. The Canon prime is faster, but no IS,
but lighter, no push-pull and can be carried effortlessly.
The work put into the project by the photographer is far more important than the gear. Always was ... always will be. Make sure your gear is rugged,
reasonable well-sealed, has proven sharp optical quality with coatings and is not the cost of a used car. Remember, you are not making money with your gear,
it is sucking money out of you.
Shortsighted