Dag was so wise that he could understand the song of birds. He consequently had a tame sparrow which flew to various countries and returned to him with tidings like Hugin and Munin to the wise god Odin.
Once the sparrow happened to land on a corn field in a place called Varva in Reidgotaland (considering the date and location, apparently Gothiscandza). The peasant who owned the field managed to hit the sparrow with a stone and killed him.
When the sparrow did not return, Dag was angry and sacrificed to the gods in order to have an explanation. He was told about what had happened and declaired war on the Goths. He landed in Reidgotaland with a great army and pillaged the land causing people to flee.
After having killed many Goths and taken many prisoners, they were returning to their ships. As they crossed the river at a place called Skjotan's ford (the weapon's ford), a thrall came running and threw a hayfork into the Swedish troops. The hayfork hit Dag on the head and he fell dead from his horse.
What news is this that the king's men,
Flying eastward through the glen,
Report? That Dag the Brave, whose name
Is sounded far and wide by Fame --
That Dag, who knew so well to wield
The battle-axe in bloody field,
Where brave men meet, no more will head
The brave -- that mighty Dag is dead!
Varva was wasted with the sword,
And vengeance taken for the bird --
The little bird that used to bring
News to the ear of the great king.
Varva was ravaged, and the strife
Was ended, when the monarch's life
Was ended too -- the great Dag fell
By the hay-fork of a base thrall![1] (http://www.sacred-texts.com/neu/heim/02ynglga.htm)