Not too bad on a D4 with high speed BIF's (different kind of bird, though :smile - most cropped a decent amount as well:I may be way off, but I don't suspect that you will see many samples posted. The image quality loss with a 2.0x teleconverter is quite significant. Also auto focus performance will suffer greatly.
No problem - I realize that those were not exactly on topic, but wanted to show that in good light a 2x TC can do pretty well on primes.Thanks so much for these shots !!