Willow grouse hatchling

We were just walking on some mountain path when we saw a bunch of these little guys hiding in the grass. It proved really easy to take a picture of them because they were under the impression we couldn't see them

I actually don't know whether this is a willow grouse or a ptarmigan, because both species live in this part of Norway.. In my limited skills of observation I happened to see a bit of white under mom's wings, so I concluded it's most likely a willow grouse.