I came across this reference in _Les religions gauloises_ by
Jean-Louis Brunaux.  In his history of Rome, Titus Livy tells
how in 349 BC a young tribune named Valerius faced a Gaulish
chief, famous for his strength and the beauty of his weapons,
in single combat.  Just as the duel commenced, a crow landed
on the young Roman's head.  Valerius took this as a sign of
good fortune and prayed to the god who sent the crow to help
him win.  The crow remained on his head throughout the fight,
attacking the Gaul with his beak and claws and finally blinding
him.  In thanks for this victory, Valerius added Corvus (crow)
to his name thereafter.

Raymond Bloch* argued that this tale, which is unlike any
other in Roman history and legend, is a Gaulish myth which
the Romans appropriated and reworked to their own benefit.
It certainly resonates with the Irish tale of Cú Chulainn
and the Morrígan (Badb), although her relationship to him
was much more complex and destructive.  (In _Land of Women_,
Lisa Bitel claims that "the Morrígan, at least, betrayed a
schizophrenic affection for Cú Chulainn which belied her
fierce nature.")

*_Recherches sur les religions de l'Italie antique_, 1976

Dennis King