How can Glaspell's Trifles be analyzed using a literary element?

In Glaspell's Trifles, Mrs. Wright, who is under suspicion for killing her husband, is compared, through a simile, to a bird. Mrs. Hale says, "She--come to think of it, she was kind of like a bird her­self--real sweet and pretty, but kind of timid and--fluttery." Mrs. Wright is likened to a bird that is pretty and has a shy nature. 
The bird is also a symbol in the play. Mrs. Hale and Mrs. Peters find the bird, dead, in Mrs. Wright's sewing box. Its neck has been wrung, and the women, sensing a motive for Mrs. Wright's murder of her husband, hide the bird from Mr. Hale, the Sheriff and the County Attorney. Mrs. Hale says, "If there'd been years and years of nothing, then a bird to sing to you, it would be awful--still, after the bird was still." They sense that Mrs. Wright killed her husband after he killed the bird, the one form of companionship Mrs. Wright enjoyed. They don't want to tell the men investigating the crime about the bird because it would help secure the case against Mrs. Wright. The bird is a symbol of Mrs. Wright's suffering in her husband's house.