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 hiding
Stirred 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.
Brute beauty and valour and act, oh, air, pride, plume, here
Buckle! […] (9-10)
The speaker lists the qualities that the bird brings together ("buckle"). That word "buckle" also suggests that those qualities almost collapse into each other (as in, "my knees buckled under the weight of my backpack and I fell down the stairs"). The fact that the speaker uses the verb act instead of the noun action might suggest the movement of the bird. The speaker is most interested, after all, in what the bird is doing, so using a verb makes sense. But the speaker also wants us make us sit up and pay more attention to familiar, everyday things (like a bird in flight), so using familiar words in unfamiliar ways might be another way to help us do that. He sure succeeded in making us pay more attention to that little word act.
[…] dapple-dawn-drawn Falcon (2)
This metaphor makes it seem like the windhover is being "drawn" by the "dawn" the way a carriage is drawn by a horse. It's kind of a funny mental image—like the bird is being pulled by the dawn.
[…] he rung upon the rein of a wimpling wing (4)
Whoa. Now the bird is like a powerful horseback rider, and his wings are the reins he's using to harness the power of the wind. It's another unexpected mental image that makes us see the bird in a new, more exciting way.
[…] then off, off forth on swing,
As a skate's heel sweeps smooth on a bow-bend: […] (5-6)
The bird changes yet again, with another metaphor: now the bird appears to be an ice skater, suddenly gliding in an arc, or a "bend."
[… ] the fire that breaks from thee then […] (10)
As the bird makes a dive toward the ground (he must have spotted a mouse or some other small animal to catch), the red on his chest flashes like fire. But the "fire that breaks from him" sounds kind of dangerous, like he's a falling star or a crashing airplane or something.
[…] shéer plód makes plough down sillion
Shine […] (12-13)
The speaker says that even a simple plough is beautiful—when it's well used, the steel of it gets all shiny. The speaker seems to be suggesting that even well-worn everyday things, like farm tools, can appear beautiful if you look at them in the right way.
I caught this morning morning's minion (1)
The word "caught" is an odd choice of words here. The speaker is using it in the sense that we'd say, "I caught a movie on Friday night"—in other words, that he saw something. But choosing the word "caught" makes it sound like he caught it unawares, or caught it in the act. Or it might make you think of "catching" a bird in a trap or a cage. What do you think?
[…] how he rung upon the rein of a wimpling wing (4)
The bird is able to harness the natural power of the wind the same way that a horseback rider harnesses the power of a horse. There's beauty and hidden danger here: the wind is incredibly powerful, but the bird is able to "rein" it in.
[…] shéer plód makes plough down sillion
Shine […] (12-13)
The image of a plough that is so well worn that it shines might seem out of place at first. The first eight lines of the poem (the octet) are about the bird's control over a powerful natural element—the wind. And the plough might seem to come out of nowhere. But a plough is often used as a symbol of man's control over the natural world, since it's a farm tool that is used to dig up the dirt to prepare it for planting. So the image of the plough actually goes pretty well with all the images of the bird controlling the wind.
High there […] (3-4)
The word "striding" seems like a weird choice of words to describe something a bird does. Birds fly, they don't stride, or take long steps (unless we're talking about Big Bird from Sesame Street or an ostrich, but you know what we mean). We usually reserve the word stride to describe the steps of someone who really knows what he or she is doing. As in, "She strides masterfully across the room and seizes the crown for herself." So the choice of the word striding here might suggest the bird's extreme skill and know-how.
[…] the hurl and gliding
Rebuffed the big wind. […] (6-7)
This bird's so tough that he's able to "rebuff," or to beat back, the powerful wind so that he can hover in place in the air.
[…] the achieve of, the mastery of the thing! (8)
The speaker is totally blown away by the bird's skill. So blown away, in fact, that he uses the verb "achieve" instead of the noun, "achievement," that we'd expect in this sentence. Maybe he's trying to emphasize the bird's action and motion by using the verb, or maybe he's trying to make us do a double-take, and to think about familiar words (like "achieve") and familiar sights (like birds flying) in new ways. Or maybe it's a bit of both. Hopkins had mad skills, after all.