While the father pelican was fishing in order to bring food to its chicks
A snake entered the nest and when it was at the point to swallow them the pelican came back and the snake slithered away.
But the little birds were already poisoned.
So the parent pinched himself and inflicted a wound on his chest: clear blood flowed from it and he feeds the chicks with his blood, in order to heal them.
This legend was spread all over medieval Europe.