An egg, a nest, a test, a flight: Drayton fits a whole life story into fourteen lines, and its hero is not a bird but the speaker's own love. He says he found his love the way you might find an eaglet, and, wanting to know whether it was truly "of that kingly kind," he puts it through the trial that old lore set for young eagles: make it face the sun. Here the sun is his lady. The young love doesn't flinch. "On her rays with open eyes it stood," proving it was hatched "for the air." Once its feathers are fully grown, it climbs the sky and, "do what I could," keeps aspiring to "my Soul's Sun, those two celestial eyes." In the closing couplet it leaves his breast and flies "after thee."
The central idea is a paradox. The speaker wants proof that his love is noble, and the proof is exactly what takes it away from him. A love strong enough to stare at its sun is too strong to stay in the nest. Behind the compliment to the lady sits a quiet confession: the lover has lost control of his own heart.
The tone helps this along. The speaker begins as a proud, slightly anxious parent. He finds, tests and hatches, and his verbs are all about ownership and management. Then comes the plain helplessness of "Do what I could." That line starts on a stressed "Do," which sounds like an exasperated shrug. The word "needsly," meaning of necessity, makes the flight sound like instinct, not choice. His pride ("brave mounting brood") and his loss sit side by side without cancelling each other.
The imagery is built on a doubled sun. First the lady is "my Sun," whose "rays" the eaglet faces. By the third quatrain she is "my Soul's Sun," and the rays have become "two celestial eyes." The possessive deepens from "my" to "my Soul's," and the staring contest turns into a meeting of gazes: the eaglet's "open eyes" look into hers. Words of height carry the rest of the story: "air," "mounting," "ascends," "skies," "aspire." The last of these works twice, since it means both rising physically and reaching for something higher. The language of rank, "kingly" and "brave," lets the lover flatter the lady while also flattering his own heart for having such good taste. Even the plumes "summ'd with sweet desire" carry the sense that the love grows up, and what matures in it is desire as much as courage.
The form is a Shakespearean sonnet in iambic pentameter, rhymed abab cdcd efef gg. Each quatrain gets a stage of the story. The first is the finding and the test, the second the eaglet's triumph, and the third its growth and ascent. The couplet then delivers the consequence. Some of the rhymes are imperfect to a modern ear: "love" and "prove," "stood" and "brood," "appear" and "air." The effect is a faint unevenness, as if the poem's own sounds don't quite settle, which suits a love that refuses to stay put.
Two details in the ending are worth noticing. The poem is bookended by the same simile: it opens "When like an eaglet" and closes "like an eaglet, flown." The comparison that starts as a way of describing his love finishes as a description of its escape. And the pronoun changes. Through the middle the lady is "her" and "those two celestial eyes," someone talked about, but in the last line the speaker turns and says "thee." The addressee only appears as the love is already flying toward her, so the poem's final movement carries us from the speaker's breast to her. The very last word, "flown," confirms that the nest is empty. There is also a small, sad detail in the phrase "where it was bred alone," which hints at a solitude the lover is left with.
What makes the sonnet worth reading is how fully it commits to its single comparison. Calling a lady a sun is an easy compliment, but Drayton doesn't leave it as one. He turns it into a short narrative with a test, a growth and a departure, and a twist in which success costs the tester everything. The conceit explains why love feels both like a possession and like something that was never quite his to keep.