The companions followed the shady wood-road, the cow taking slow steps and the child very fast ones. (1.4)
This brief image shows us how childlike Sylvia is. This is important to establish off the bat, because Sylvia will go through some changes by the end of the story—and the story's pretty stinking short.
The thought of the great red-faced boy who used to chase and frighten her made her hurry along the path to escape from the shadow of the trees. (1.4)
Although Sylvia is scared of people, she's especially scared of men, or boys as the case may be with the "red-faced" kid. As it turns out, this brief memory will be interrupted by the entrance of another man who wants to leverage her youthful innocence to his own ends.
Suddenly this little woods-girl is horror-stricken to hear a clear whistle not very far away. Not a bird's-whistle [...] but a boy's whistle, determined, and somewhat aggressive. (1.5)
In Sylvia's mind, men are "determined" and "aggressive"—two things that she doesn't exactly find comforting. Can you blame her for being scared when the hunter first approaches?
She did not dare to look boldly at the tall young man, who carried a gun over his shoulder. (1.5)
Sylvia is intimidated by the young man and his deadly weapon. It would be impossible not to mention the (ahem) phallic symbolism inherent in a gun and the way this symbol relates to the story's theme of innocence. For more on this, check out the "Symbolism, Imagery, Allegory" section.
She had never seen anybody so charming and delightful; the woman's heart, asleep in the child, was vaguely thrilled by a dream of love. (1.26)
Like many a young girl, Sylvia masks her initial attraction with fear and revulsion. Although she is way too young for this guy, this is the first time she's had a real crush. In fact, he's probably the first hunk she's seen around these parts in some time.
She grieved because the longed-for white heron was elusive, but she did not lead the guest, she only followed, and there was no such thing as speaking first. (1.27)
Sylvia is as tomboyish as they come, yet she transforms into a quiet, subservient girl in the company of the young man. Is she scared to show her true self? Or does the hunter's relative age simply intimidate the young girl?
What fancied triumph and delight and glory for the later morning when she could make known the secret! It was almost too real and too great for the childish heart to bear. (2.2)
Sylvia thinks that she will go through a transition—a coming-of-age experience, if you will—when she leads the hunter straight to the white heron. But reality turns out to be a little different.
The young sportsman and his old hostess were sound asleep, but Sylvia's great design kept her broad awake and watching. She forgot to think of sleep. (2.3)
Sylvia is like a child eagerly awaiting Christmas morning. Although she doesn't entirely understand the gravity of the situation, she understands (on some level) that this is an important moment in her young life.
He was sure from the way the shy little girl looked once or twice yesterday that she had at least seen the white heron, and now she must really be made to tell. (2.11)
Finally we get to see the hunter's perspective on the situation. In truth, the guy seems kind of like a manipulative jerk—what kind of guy would talk about a nine-year-old like that? Ugh.
Many a night Sylvia heard the echo of his whistle haunting the pasture path as she came home with the loitering cow. She forgot even her sorrow at the sharp report of his gun (2.14)
This incident weighs on Sylvia's mind well into adulthood. She understands that this was an important growing experience for her and presented a very different path that she very well could have taken.