As long as the ordinary means of communication are working satisfactorily, birds are not used. But when a barrage is laid down and the telephone-wires are destroyed, resort is had to the pigeons. When an advance-party has pushed far ahead of the main force it, too, relies on this method of liaison. In short, when every other method of liaison has failed or is unavailable, important messages are intrusted to the birds. The messages are written on fine tissue-paper, folded into a small wad, and inserted in the aluminum holder which is attached to the leg of each pigeon. The bird is then released, and in spite of the terrific din and confusion of battle, in spite of the enemy shotgun squads, composed of expert shots, whose duty it is to pick off carrier-pigeons, it wings its way through shell and gas barrages to its loft in the rear of the lines. I might mention in passing that though birds are frequently killed while in their baskets by exploding shells, and others die from long confinement without food or care in the trenches, those that survive become accustomed to the roar of cannon and never suffer from shell-shock. On reaching his loft the bird hurries into it through an opening which permits of entry but not of exit, the dropping back of the little door ringing a bell which announces the arrival of a message from the front, whereupon eager hands strip the cylinder from the leg of the bird, the message which it contains being relayed to headquarters by telephone or despatch-rider.