They were going away from whatever light there was, and striking deep into the woods, but their feet were familiar with the path, and it was no matter whether their eyes could see it or not. (1.1)
In this case, Sylvia really <em>does </em>know the forest like the back of her hand. This passage also serves to remind us how connected Sylvia is to animals—she refers to herself and her cow as "we." Aw.
The good woman suspected that Sylvia loitered occasionally on her own account; there never was such a child for straying about out-of-doors since the world was made! (1.2)
Even Sylvia's grandmother can see how attached Sylvia is to nature. But if the previous passage is any indication, then Sylvia's not necessarily loitering—she's just taking it all in.
It was a good change for a little maid who had tried to grow for eight years in a crowded manufacturing town, but [...] it seemed as if she never had been alive at all before she came to live at the farm. (1.2)
Now we find out that Sylvia was actually born a city girl, despite her obvious fear of people. Growing up in the city likely makes Sylvia more appreciative of the calm that nature has to offer.
She was not often in the woods so late as this, and it made her feel as if she were a part of the gray shadows and the moving leaves. (1.4)
At times, we see the boundaries between Sylvia and the natural environment breaking down until there's no distinction between the two. This effect becomes even more pronounced as the story continues.
Suddenly this little woods-girl is horror-stricken to hear a clear whistle no very far away. Not a bird's-whistle, which would have some sort of friendliness, but a boy's whistle. (1.5)
This is telling: Sylvia would be delighted at the sound of a bird, but is terrified at the sound of another human. In a way, she has already explicitly chosen the natural world over man-made civilization.
"Dan, my boy, was a great hand to go gunning," she explained sadly. "I never wanted for pa-tridges or gray squer'ls while he was to home. He's been a great wand'rer [...] Sylvy takes after him." (1.15-16)
It turns out that Sylvia isn't the only member of her family to fall in love with nature. There's a dark side to this, however—no one knows where Dan is anymore. Is city life just too much for a nature lover like him to handle?
"There ain't a foot o' ground she don't know her way over, and the wild creatur's counts her one o' themselves." (1.16)
Sylvia's grandmother is proud of Sylvia's attachment to nature—she knows how rare this type of connection is. She made a wise decision in choosing Sylvia to live with her, didn't she?
"Anything but crows, I tell her, I'm willin' to help support—though Dan he had a tamed on o' them that did seem to have reason same as folks." (1.16)
This is pretty bold when you think about it: Sylvia's grandmother doesn't even like crows, but is willing to say that they are as smart as people. Although we don't see Mrs. Tilley bonding with nature as much as Sylvia, this is an indication that she might've been a tree-hugger back in the day herself.
"So Sylvy knows all about birds, does she? [...] I am making a collection of birds myself. I have been at it ever since I was a boy." (1.18)
Of course, by "collect," the hunter means "shoot." Although the hunter has a strong bond with nature, it's something entirely different from Sylvia's. She wants to live with nature; he wants to dominate it.
Sylvia would have liked him vastly better without his gun; she could not understand why he killed the very birds he seemed to like so much. (1.26)
Sylvia is well aware of the irony behind the hunter's professed love of nature. In truth, he only loves nature when he is able to put it under his own control. This serves to heighten the contrast between Sylvia and the hunter even further.