I am not a wildlife photographer normally but a friend took me to a Wildlife Trust so that I could try the D500 with the 300mm PF lens, I took all the shots in Manual and the EXIF data can be seen at the bottom right corner of the image.
I did use the 1.4 convertor for some of the longer shots and did not notice any reduction in focus efficiency / speed which is amazing with this combo.
Apologies if this is image heavy and for interested parties the full set from the day can be seen here -
571 Photography