In ancient Celtic times animals were depicted in stylized form rather than in realistic form.  This design is of an eagle, a powerful Celtic god who often represented prophetic knowledge in their mythology.  Having two sets of wings emphasizes that power.  Eagles were symbols of omniscience.  In this depiction the salmon in the claws of the eagle represents the hopes and aspirations of men that are being carried to the heavens.  The salmon was also sacred to the Celts and consulted for its wisdom and foreknowledge.