Robin's and Spring?

As I walked up my driveway to get the mail and drag in the garbage can I noticed some birds on my neighbor's lawn. Getting closer to then I could clearly see the "Red Breasts" of the Robins searching for food in the frozen ground. That's right, FROZEN! It must be in the twenties today with a wind chill factored in to bring it down into the teens. Why are there 7 Robins looking for food in the ground when a worm couldn't wriggle through the solid ground if it wanted to? Beats me. Hopefully the Robin's know better than I do.