Christian Symbolism of the Crane in a Medieval Bestiary
The Definition and Meaning of the Crane as a Religious Christian Symbol - Allegory and Moral
The sentinel crane represent those who provide goods for others in common, and watch over the obedience of their brothers, protecting them from devils and the incursions of this world. The stone held in the claw is Christ; the claw, the disposition of the mind, so that the one who stands guard over himself or others should carry the stone of Christ in his mind. If such a man falls asleep in sin, Christ the stone will fall from his mind. Then he must cry out by means of confession. The change of color in old age refers to the elderly when they repent of their sins.
Reference to the Crane in the Bible
(Isa. 38:14; Jer. 8:7). In both of these passages the Authorized Version has reversed the Hebrew order of the words. "Crane or swallow" should be "swallow or crane," as in the Revised Version. The rendering is there correct. The Hebrew for crane is 'agur, the Grus cincerea, a bird well known in Palestine. It is migratory, and is distinguished by its loud voice, its cry being hoarse and melancholy.