Her breast is fit for pearls — Apple Tree

Her breast is fit for pearls, 1
But I was not a "Diver"-
Her brow is fit for thrones
But I have not a crest.
Her heart is fit for home-5
I-a Sparrow-build there
Sweet of twigs and twine
My perennial nest.
(F.121/J.84)
[1] breast:: the front part of a tree. pearls:: pearl-spotted barbets.
[2] "Diver":: one who thinks deeply, dives into a subject. Barbets will "sit nearly motionless for hours."
[3, 4] thrones, crest:: nests suit for eagles.
[5] heart:: center part.
[7] Sweet:: sweet bough, an apple tree,
[8] perennial:: apple tree is a perennial plant.

Trachyphonus Margaritatus. The Pearl-spotted Barbet. ─ List of the Specimens of Birds in the Collection of the British (1848)

Mr. Swainson has thus graphically described the habits of one of the South American Barbets . . . There is something very grotesque in the appearance of all the Puff-birds; and their habits, in a state of nature, are no less singular. They frequent open cultivated spots, near habitations, always perching on the withered branches of a low tree, where they will sit nearly motionless for hours; unless, indeed, they descry some luckless insect passing near them, at which they immediately dart, returning again to the identical twig they had just left, and which they will sometimes frequent for months. ─ A Popular History of Birds (1855)