What happens with Tita and the pigeons? Why is she nurturing them?

In Chapter Five, we find that Tita has no passion for life except for feeding worms to a baby pigeon that survived a visit by the rebel army. A few days earlier, when the revolutionary army came to the ranch, Tita and Chencha hid in the cellar while Mama Elena defended her property. Gun in petticoat, Mama Elena threatened the army not to touch anything in the house but she allowed them to take stock of the corncrib and stable. The army removed all the birds from the dovecote above the house except for one baby dove, which Tita later found and rescued.

The pigeon later dies and Tita refuses to come down from the dovecote. Chencha discovers her there covered in feathers, stroking the dead pigeon that she had been feeding, but Tita refuses to come down. Mama Elena then summons Dr. Brown to take Tita to the asylum.