The point being, don't fixate on gear. Technique beats gear every time. One of the best techniques to learn in bird photography is to be slow and quiet..... although that said, I would not refuse a 1DX and a 600II if it were offered
Location > gear
Time spent at location > gear
I'd rather shoot with a Canon S2 in Yellowstone for a year than a high end camera and lens combo for two weeks.
I bet if I had a 1D X and a 600/4 II I'd create 100x more great photography in two weeks than you would with your Canon S2 in a year. I have absolutely zero doubt, as a matter of fact.
The odds of getting truly great photographs in nature increase exponentially based on time in the field, not what gear you have.
First, you have to get out there. Second, you have to stay out there in all conditions. Then you need to apply technique, and hopefully a bit of luck will come your way, but don't count on it.
Time can be a factor, but gear is not immaterial. If I wanted to get a shot of bears, I'd much rather have a 1DX/5D III and a 600/4 + 2x TC, or a 7D and 600/4, than anything else.
I joke about my tamron 150-600 being my polar bear lens because that's as close as I want to get to one. Yes, I could use a 50f1.8 to take the shot, but when you show the picture and say "see that pixel, it's a polar bear" they are not impressed
There are definitely times when you can not get close, or do not want to get close. For those times, there is no substitute for gear. As someone who has shot with the Tamron and the 600F4, there are times when neither is long enough. At least the 600F4 plays well with teleconverters.... Don't bother with the Tamron.
That said, I still believe that most of the time technique beats gear. It's when we are at the limits that the gear becomes truly important and most people never get that far. People like Jrista are not typical. His bird portraits are at a level where great technique and great gear are needed to get that level of shot. Myself, I am still learning and only occasionally reach the limits of my gear, and to keep things in perspective, remember that most cameras are left in program or "green box" mode. For all those people, technique is far more important than gear.