Why does the young man spend several nights at Mrs. Tilley’s cottage?
In the story, the young man is an amateur ornithologist who has been hunting and appears to have lost his way. At least, that is what he tells Sylvia, whose grandmother, Mrs. Tilley, promptly offers the stranger lodging for the night.
Eventually, the young man admits that he enjoys hunting birds and having them 'stuffed and preserved, dozens and dozens of them...' He tells Mrs. Tilley and Sylvia that he is particularly interested in a white heron he has seen flying close to their home. Meanwhile, Mrs. Tilley's pride in Sylvia's knowledge about surrounding bird species causes her to boast about her grand-daughter's prowess.
The young man's ears perk up when he hears that Sylvia knows all about the birds near her grandmother's home. He offers ten dollars to them if Sylvia can lead him to the white heron. Yet, Sylvia finds that she cannot bring herself to tell the stranger where the white heron lives. In the end, he leaves empty-handed. His initial intent was to track and hunt the white heron, and that is why he stays at Mrs. Tilley's home. However, he finds his goal thwarted by a little girl who loves her avian friends more than she values monetary gain.