My father, a US citizen, who has a dual citizenship and currently lives in Europe, is going to move back to the United States, and wants to wire all of his savings from the european bank account to the US bank account. The amount greatly exceeds $13,000. Does he have to pay any taxes on the money transferred? Does he have to file anything with IRS? Thanks for any help!

No, there is no tax involved.
Your father must file U.S. tax returns if his worldwide income exceeds filing requirement.
Read: Your U.S. Tax Return: U.S. Citizen or Resident with Foreign Income

Hopefully your father has been filing U.S. tax returns and including the interest income from the foreign bank accounts on his U.S. tax return. If he hasn't, he should amend his U.S. tax returns to include the interest. Also, if he hasn't filed Form TD F 90-22.1, then he should file those as well. Beyond these items however, transferring the cash from overseas to the U.S. should not be taxable to him.