How fresh the air, the birds how busy now.
In every walk if I but peep I find
Nests newly made or finished all and lined
With hair and thistle down, and in the bough
Of little awthorn huddled up in green,
The leaves still thickening as the spring gets age,
The Pinks quite round and snug and closely laid,
And linnets of materials loose and rough,
And still hedge sparrow moping in the shade,
Near the hedge bottom leaves of homely stuff,
Dead grass and mosses green, an hermitage
For secresy and shelter rightly made,
And beautiful it is to walk beside
The lanes and hedges where their homes abide.
Oxford Major Works, pp. 207-8
John Clare wrote dozens of poems about bird nests. "The Ravens Nest", "The Moorehens Nest", "The Sky Lark Leaving Her Nest", "The Yellowhammers Nest". The one I include here is unusual for covering multiple types of nests. But the details about nesting materials and the plants that house the nests are typical - this is the sort of thing Clare always includes.
Clare knew what nests were for. Most of his nest poems include descriptions of the eggs, too:
from The Woodlarks Nest
As safe as secresy her six eggs lie
Mottled with dusky spots unseen by passers by
from Hedge Sparrow
Its eggs in number five of greenish blue
Bright beautiful and glossy shining shells
Then there are "Hares at Play", "The Badger", "The Tame Badger", on and on. They are all little natural histories, by a perceptive and experienced observer.
These poems generally do have some sort of point - as in the last lines of "Birds Nests" above, about man's coexistence with the natural world, and the poet's pleasure in knowing the birds and nests are around him. The knowledgable detail, though, is what always amazes me, more than the moral. Some twentieth century poets would try to recapture this real attention to nature - A. R. Ammons book Uplands is an example. I don't know of anyone who was more successful than Clare.
My understanding is that Clare scholars have teamed up with English naturalists to comb through these poems, and that Clare's knowledge is first rate. He only knew his little corner of Northamptonshire, but he knew it all, birds, animals, insects, and eels.
The header is also from The Woodlarks Nest, pp. 235-6