I noticed the same in my garden a couple of days ago and assumed it was a blackbird, but I didn't actually see him doing it.
Blackbirds regularly feed by turning over leaf litter for small invertebrates. In my garden the pattern in your picture was under a hedge in a favourite blackbird spot. The confusing thing is: could he have thought he was looking for insects? I don't think so - they're not that daft. So was he "drinking" the snow? That's a possibility. I've been putting out water every morning, and replacing it as it freezes. The blackbirds seem to be the thirstiest birds and were even pecking through thin ice to get the water beneath.
One possibility is that they become more thirsty as they are forced to vary their diet. Normally they get a lot of moisture from the little creatures they consume. When they have no choice but to eat bread and scraps, they probably have to top up their water levels.
