Sometimes The young chicks will not only hitch a ride on the parent's back, but will also hide close to the parent's body under a wing.
A young loon was practicing flight in September. I had found two youngsters with their parents. One of the young loons was larger and dove deeply with one of the parents. I don't believe the smaller one was flying yet and it was constantly begging for food though the parent ignored it. At one point, I saw it rowing which is something they do to strengthen their wings. Parents will actually leave them soon and they will be on their own to finish up their flight skills necessary for their first migration to the ocean. I believe this is the larger of the offspring practicing flying. It and another adult were circling the lake which seems like wasted energy for an adult unless it was encouraging the young one to fly. I saw some crashing on landing across the lake that looked like it could be a young bird. This one flew over my me in the kayak. Pretty exciting!