Yes it is a weight bearing exercise. When your feet his the surface it causes bone to get stronger. I am sure thre is a more scientific explanation but this is the simple version.

According to my doctors ans sheet logic, of course it is. Your legs are 'bearing' the full weight of your body with every step. Wearing a weighted vest, or carrying something heavy, can recall certain the load on other muscles but, if the person is also walking, the legs are bearing the weight. When I first started reading about osteoporosis, I came upon a study as to why professional cyclists tend to have early-onset, and severe, osteoporosis. The conclusion was that they frequently run a calorie deficit to lower body weight. And they spend training time on cycles. So they don't have body fat, thus also lower estrogen, to help bone health. And their lean frames are insufficient to make walking a good weight-bearing exercise.