The comparative security afforded to birds by island-retreats could not fail to have attracted the attention of man from the very dawn of his reasoning faculties, and it is probable that, as soon as he acquired sufficient skill to enable him to cross a creek or a river, he occasionally resorted to such means of protection. From the natural to the artificial island was but a stage of transition which, in the course of time, would be readily bridged over by his progress in mechanical knowledge.