Returning Skylarks

The skylarks, having completed their breeding cycle suddenly disappeared from the fields around my home. They have now returned. There are about ten individuals, which I take to be family parties and they are feeding on the stubble fields. One even broke briefly into song the other day as the autumn temperature rose to summer levels, but generally they fly around in a flock calling incessantly. The only mystery is: Where did they go to for the month or so whilst they were absent?