That the lowest boughs and the brushwood sheaf Round the elm-tree bole are in tiny leaf, While the chaffinch sings on the orchard bough (5-7)
Spring is here, which means both renewal and possibility. The budding leaves and singing finch here are both potent symbols of the freshness of experience that we associate with this time of year.
And the whitethroat builds, and all the swallows! Hark, where my blossomed pear-tree in the hedge Leans to the field and scatters on the clover Blossoms and dewdrops—at the bent spray's edge— (10-13)
The whitethroat is hard at work here, building… something. We're going to guess "nests," but it could also be a sweet soapbox derby racer. In any case, along with the pear blossoms, these birds create an image of nature that's productive and filled with energy. The swallows? Well, they're also there. Maybe they're just on break.
That's the wise thrush; he sings each song twice over, Lest you should think he never could recapture The first fine careless rapture! (14-16)
We thought that owls were the wise birds, but we guess that thrushes also know a thing or two about a thing or two. In this case, the most striking aspect about this bird is just how over-the-top happy it is. Just when you thought its song sounded so happy that it couldn't be repeated—boom. It does it again. That's one bird who's happy to be there.
And though the fields look rough with hoary dew, All will be gay when noontide wakes anew The buttercups, the little children's dower (17-19)
Don't be fooled by all the dew. The speaker promises that the natural beauty of the fields will soon be on display. He even throws in some children to sweeten this postcard-friendly image of the English countryside.
—Far brighter than this gaudy melon-flower! (20)
If someone were to show you a melon flower, you're first reaction would probably not be "How gaudy." Sure, it's a big, and it's definitely yellow, but after all, it is a flower. By and large, folks tend to be pro-flowers. The speaker's reaction to nature here, though, shows how our emotional frame of mind can influence the way we see our surroundings.