Shelley's poem begins as a small domestic comedy and ends as a love song to a bird. In the dusk, Mary (the poem's Mary is usually understood to be his wife, Mary Shelley) asks whether he can hear the Aziola crying nearby. He has never heard the name, and he jumps to the wrong conclusion: "I, who thought / This Aziola was some tedious woman." His relief at discovering that she is only "a little downy owl" is the poem's first movement. Its second is a quiet change of heart, in which the creature he nearly dreaded becomes something he loves.
The first stanza is built like an anecdote. The lines are uneven, some long and chatty, such as "In dusk, ere stars were lit, or candles brought," and some clipped, such as "And I, who thought." The effect is of speech that stops, starts and corrects itself. The rhyme is just as loose. "Cry" and "nigh" open the poem with a neat pair, but then "woman" is matched with "human," a slightly bumpy feminine rhyme that suits the joke. It is as if the poet's own assumption were being gently teased. The word "human" matters more than it seems. His relief is that the cry is "nothing human, / No mockery of myself to fear or hate." Judging by those words, he expects a person to be a source of embarrassment or irritation, and an owl cannot be that. The tone is light, but it admits a real social nervousness. Mary, meanwhile, "saw my soul, / And laughed." One short phrase carries a whole marriage's worth of understanding, and her teasing reassurance, "Disquiet yourself not," is affectionate rather than unkind.
The second stanza changes mode. The chatter drops away, and Shelley addresses the owl directly: "Sad Aziola!" The poem moves from story to apostrophe, from "she" to "thee." The setting widens at the same moment. In place of one dim room we get "wood and stream, meadow and mountain-side, / And fields and marshes wide," a landscape built from paired nouns that seems to stretch with each line. The word "eventide" quietly echoes the earlier "dusk," so that the owl's music belongs to the same fading light in which the little scene took place.
The heart of the stanza is a list of denials: the owl's music is unlike "voice, nor lute, nor wind, nor bird." The repeated "nor" strips away every comparison one might reach for, human song, instrument, weather, even other birds. Calling a bird unlike any bird is a nice paradox. It suggests a sound that can't be translated into familiar terms. The cry "the soul ever stirred" in a way nothing else did, and he finishes that thought with another paradox, "Unlike and far sweeter than them all." Here the word "sad" does the real work. It appears three times in the stanza, and each time it is attached to something loved. The poem treats sadness as a source of beauty rather than something to escape, a very Romantic idea, though Shelley expresses it here without grand language.
The ending is the poem's most careful piece of design. The final lines, "from that moment I / Loved thee and thy sad cry," rhyme "I" with "cry," and "cry" was the poem's very first rhyme word. The poem comes full circle, and the sound that opened it as a puzzle closes it as an affection. The last line is also the shortest in the stanza, and its brevity makes it sound like a plain confession.
What makes the poem worth reading is its modesty. Shelley is famous for soaring, ambitious verse, and a famous bird poem such as "To a Skylark" looks upward at a distant singer. Here the bird is small, sad and nearby, and the real subject is how a listener's mind changes. Embarrassment becomes relief, relief becomes tenderness, and a name that sounded like a social threat turns into a sound he cherishes. The poem suggests that we often fear the unknown for the wrong reasons, and that what we feared may turn out to be the thing we love.