a couple small nitpicks:
pretty much all birds have a nicitating membrane/third eyelid - in fact, even some mammals still have them! i understand that that part of the guide had to go Somewhere, of course, so i'm not judging you for putting it in the falconid section - it just might've been nice to specify that it's not exclusive to that group c:
and, as others have pointed out, falcons probably aren't that closely related to other birds of prey. i'm not sure if that was known when this was made, though, so it's probably not a big deal tbqh
that said, this series is still very helpful and informative, and i'm sure many bird-loving artists (myself included) are very glad you made it. guides like yours are life-savers.