As the content of this video is so exceptionally good, I really have to be very, very careful with any constructive criticisms.
I have watched this video twice now and really enjoyed it. I particularly liked watching the butterfly emerging and wing drying towards the end of the video.
In my opinion, overall this video should get the highest praise.
I want to give a few of my thoughts as to how I think this video could be improved but before I do so, I would like you to understand that I am coming from the perspective of only having ever seen a grand total of 1 White-letter Hairstreak and that was last year

. So I am not an expert and this video has clearly been made by experts.
I think the tree-top behaviour could be seen more clearly with a longer lens but I understand how hard this is (without digital zoom

).
The next stage could be to get a narrator if you can find someone with the right voice (this is something I am not very good at) This could reduce the length of the video by removing at least some of text, maybe also helping the video to "flow" a bit better. My personal preference is to present the whole thing widescreen (without the black bars either side). That could be a "red herring" so I will shut up now,
best wishes,
Philip