Baby chicks are enjoying some (well supervised) freedom in the unused cold frame

I have a covering to deter hawk attacks, and I visit them every ten minutes or so while they are outside (which is not long, because they will become chilled) to make sure snakes aren't after them, but they understood dirt and its functions immediately,without the example of a mother hen, and began scratching and dust-bathing as soon as they could.  Here's a video of them having fun.