"Birds" represent rational concepts in the external man and intellectual concepts in the internal man.

Flesh signifies man, and spirit signifies the influx of truth and goodness from the Lord, as in Joel 2:28. In Isaiah 31:3, flesh signifies what is man's own, and spirit life from the Lord. To eat the flesh of another signifies to destroy his proprium.

(Odkazy: Apocalypse Explained 654; Joel 2)