How is "A White Heron," by Sarah Orne Jewett, a work of literary realism?

An author of a work of literary realism aims to depict the everyday world in a realistic -- as opposed to idealistic -- way.  This is what Jewett attempts to do through her description of the banal, commonplace activities of life on a farm: Sylvia's nighttime, muddy search for Mistress Moolly at the story's beginning, cow-milking, berry-picking, toad-watching, and keeping company with chickens.  Nothing is idealized or romanticized; the effect of nature on Sylvia is...

An author of a work of literary realism aims to depict the everyday world in a realistic -- as opposed to idealistic -- way.  This is what Jewett attempts to do through her description of the banal, commonplace activities of life on a farm: Sylvia's nighttime, muddy search for Mistress Moolly at the story's beginning, cow-milking, berry-picking, toad-watching, and keeping company with chickens.  Nothing is idealized or romanticized; the effect of nature on Sylvia is immense, to be sure, but there are no descriptions of, for example, some blissfulness that nature imparts to the child.  Rather, Jewett simply talks about Sylvia as though she were a part of the nature she so loves, comparing her throughout the story to a flower, a bird, even a star. 

Further, the opposition Jewett establishes between Sylvia, a representative of nature, and the stranger, representative of "civilization," helps to establish the story's realism.  She depicts the steady encroachment of the city on the wild and the damage to nature that such trespass inflicts.  The stranger nearly corrupts the innocent Sylvia into betraying the heron by offering her money and gifts, by flattering and charming her.  He isn't evil, but it seems as though he does not understand the danger he, and his way of life, pose to her and her woods.  By the end, after Sylvia has decided not to tell him where the heron is, and he leaves, she thinks of "the piteous sight of thrushes and sparrows dropping silent to the ground, their songs hushed and their pretty feathers stained and wet with blood."  Such a true-to-life, matter-of-fact description of the stranger's way of appreciating nature helps to further mark this text as a work of realism.