As with most poetry, answers will vary based on personal interpretation. That being said, the speaker is displaying an awe for nature here, and I think “reverent” is a word that succinctly sums up her attitude towards the bird. She is in her own backyard, yet she uses masterful language to describe the creatures in it in a stunning way; in her hands the garden is as interesting as the Amazon. She appears to be awestruck that she got to witness this encounter at all, given the tendency of most birds to flee at the slightest hint of danger. It’s why she says, “He did not know I saw -“ and why she goes on to observe that “He glanced with rapid eyes … Like one in danger, Cautious.” It makes the fleeting moment all the more meaningful because it could end at any moment. And even when the bird does leave, it leaves in such spectacular fashion, with some of the most vivid description in Dickinson’s entire oeuvre. Every single moment in this poem is described with immense care, and every single moment is its own work of art.