The mother bird knows which of her eggs contain the best offspring
The orphan bird lives in India in a sea called "la mer darenoise" by Pierre de Beauvais, who uniquely describes this bird in his Bestiaire. It has a crest, its neck and chest are like those of a peacock, it has the beak of an eagle, the feet of a swan, and the body of a crane. Its wings are red, white and black. It lays its eggs on the water, and as soon as it does, the chick grows inside the shell. The mother can tell which eggs hold the best chicks: the good eggs float a little below the mother, while the bad ones sink to the sand at the bottom of the sea. When it is time for the eggs to hatch, the good ones rise up under the mother's wings, where the chick come joyfully forth and are led to their father. The bad eggs hatch where they are, at the bottom of the sea, and the young birds must live there in darkness and grief.
This animal is only described in the Bestiaire of Pierre de Beauvais.
The mother bird represents Christ, the eggs are the people of the earth, the chicks in the eggs are their souls. Christ knows immediately which are the people with good souls; these are the ones which stay close, while the bad ones sink into sin. At the time of judgment, Christ takes the good souls to meet God; the bad souls remain in the darkness and grief of hell.