Roos

Some of it is grit hunting too. Put insoluble poultry grit out and see whether the probing drops off.

Normal, and the trough is the fixable part. They dabble and dig wherever the soil is wet, so anywhere they drink or splash turns into a pit remarkably fast. Put the water on gravel, pavers or a raised platform with somewhere for it to drain, and move the containers around rather than leaving one spot to be destroyed.

The probing along the fence is foraging. Soft soil after rain gets worked over for roots, shoots, worms, grubs and seeds, and repeated attention to the same patch becomes a hole.