Skylarks feeding on caterpillars

The skylarks departed a few weeks ago from the fields around the house, however, they have returned in numbers (around 30). They are particularly flocking on a field that has been seeded with what appears to be charlock. I can't be certain as the plants have been virtually stripped of all their leaves by caterpillars. Interestingly, the farmer has had soil tests done on this land as it did not crop at all well last year, I suspect therefore that this was a green manure with nitrogen fixing properties. Whatever the case, the plants have not been sprayed with insecticide and so the caterpillars have flourished. From what I could see, the skylarks have been feasting on this late season source of food. A few meadow pipits have also appeared to take advantage.