The sound device used in the first and third lines of 'Birches' by Robert Frost is alliteration.
Alliteration is the sound device used in the first and third lines of Robert Frost's poem, 'Birches.' Alliteration is the repetition of consonant sounds at the beginning of words. In this case, the 'b' sound in 'birches bend' and 'boy's been swinging' showcases the use of alliteration.
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