Pecking in the mud

[Col1948]

I only have 4 hens that free range in my back garden, lots of grass plus a big shrub they like to go under, their coop is also in the back garden.
In the last few weeks I've noticed two areas where they have pecked all the grass up, and now it's just mud, but they seem to like going in those areas and peck away. They go all around the garden but regularly go back to these two spots, to me there is nothing there only mud but what is it they find to peck at?

Col.

 

[SueT]

They are probably finding something you don't see. One of my hens pulled a worm out of the mud today.

 

[chickens really]

Yep...Yummy roots or bugs...