Tidings - The word is not in the original. The sense rather is “to bring them to Gath,” as captives and slaves. The prisoners taken would naturally have been part of the spoil, but David dared not to bring them to Gath lest his deceit should be discovered. Obviously these tribes were allies of the Philistines.
Related Commentaries of 1 Samuel 27:11
1 Samuel 27:11
11 And David saved neither man nor woman alive, to bring tidings to Gath, saying, Lest they should tell on us, saying, So did David, and so will be his manner all the while he dwelleth in the country of the Philistines.