You did a fine job tracking these small targets with your set up. A nice showing of how the subject can be of good interest even though it does not fill the frame, some nice environment and space keyed up the subject here.
The real answer is 1200mm... no wait, 1800mm ;-). +1 with Karl......
Many people fail to realize that feather detail and iris/retina/cornea detail is not needed all the time....I love your shots here...shows the habitat/environment. Well Done !
