Your field technique resulted in some great close-ups! Slow and low is the way to go. I watched a friend of mine slowly approach an American Bittern, took him almost a half hour inching his way through two feet of water on his knees, in waders, just as he was within good camera range another photographer came sloshing through the water, standing up making all sorts of splashing sounds, needless to say the bittern took off before any shots were taken! The verbal exchange afterwards was quite impressive! Yes, it's interesting to see all the fine details you can miss until you study detailed images like yours.