The Physiologus says of the partridge that it steals and hatches the eggs of other birds. However, when the chicks grow up and learn to fly, they each fly away to their true parents and leave the partridge alone. The interpretation is that the devil may sieze the spiritually young, but when they grow up they seek their true parent, God.
The Epiphanius version says that the partridge appears to lay many eggs, but in reality is only stealing them. No mention is made of the grown birds flying to their true parents.
The partridge in the van der Borcht copperplate engraving below may be in the process of stealing eggs from another bird's nest, or may be caring for those she already stole.
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In the woodcut below (from the Rome, 1577 edition) the partridge is probably intending to steal eggs from the nest at the left.
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Properties of the Pelican 
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