In the poem "Crossing Willow Bridge" by Lorna Crozier, what are the contrasting stages of life between the mother and dog?

In the poem "Crossing Willow Bridge" by Lorna Crozier, the mother is getting old and infirm, while the dog, a black lab, is young and full of energy and life. The contrast between the two is vivid, and provides the images that make up the essence of the poem. The speaker is walking with her mother's arm in hers over a willow bridge on a farm. When the bouncing lab suddenly appears, she is afraid that it will "knock (her) mother over," because her mother, who is "seventy-six this year," is "suddenly...unsteady on her feet."

The depiction of the mother, in the frail autumn of her life, is juxtaposed with that of the lab, who is "all energy and muscle, and too much love, he bumps (their) legs." The dog, in the prime of his life, is wild and unrestrained, and he "swings around, gathers everything he is and flies" toward the speaker and her mother. The aging mother is fragile, and tentative in her movements, while the young lab is hardy, exuberant, and unfettered. Tying these opposing figures is a third image, that of the water running under the characters' feet. The river represents time, "how it runs ahead" inexorably; the speaker laments, "how little time we have to love each other." Near the end of the poem, the speaker states clearly the writer's message - the "walk becomes a journey, the dog, the winter rains coming on." The winter rains represent aging; for the mother, the rains are coming, but not so for the dog, who stands for youth, the other end of the spectrum of life.