What does the speaker think of when he sees birches bend to left and right in poem Birches?

When the speaker in Robert Frost's poem "Birches" sees birches bending to the left and right, he is reminded of the resilience of nature and the human spirit. He imagines the birches as children who are being whipped by their father, but who continue to stand tall and strong. This image reminds the speaker of his own childhood and the challenges that he has faced. He realizes that, like the birches, he has also been whipped by life but has always managed to endure. The birches also symbolize hope and renewal. The speaker sees them as a sign that, even in the darkest of times, there is always the potential for new growth and new life.