Thank you for the considered reply. I am an admirer of your photography, so I am even more pleased you commented.
I think the bottom line is to lower my expectations of the gear I have and the gear I might acquire.
The key point is to fill the frame. I would prefer to avoid cropping as much as possible. Point taken on the Coyote, but it was an adventure I wanted to illustrate even at the expense of a poor picture. Your comment that this would not work even at 400mm is a reality check. I was avoiding the 400 because of cost and portability.
I will have a look at Sigma, but I was hoping for something that worked with the Nikon Tcs.
I tried the 300 f4 and was not impressed with the copy I tried. Maybe I should try that again - the 1.4 plus the 300F4 would be in budget for sure and would easier on the budget.