I caught this morning morning's minion, king-dom of daylight's dauphin (1-2)
The speaker is so wowed by the bird that he almost seems to be tripping over his tongue in this line—he repeats the word "morning" and repeats the M sound. His amazement overflows the first line so dramatically that the word "king-/dom" is actually broken up over two lines.
[…] My heart in hidingStirred for a bird […] (7-8)
This is the most straightforward that the speaker gets: he tells us that his heart is deeply moved. And by what? By a bird. It might seem kind of silly to get all wound up and awestruck about something as everyday and humdrum as a bird in flight, but that's the point of the poem: there's something beautiful hidden in even the most common things.
[…]—the achieve of, the mastery of the thing! (8)
The speaker explains what it is about the bird that really gets to him. It's the bird's total control and mastery. The bird seems so perfectly designed for what he's doing, and is so absorbed and skilled at hovering on the wind, that the speaker is totally blown away.