Bonus withholding
Are the Federal withholding rates different for bonuses versus regular income?
Are the Federal withholding rates different for bonuses versus regular income?

No. However, the bonus could push the pay into the next tax bracket.


IRS Publication 15 (Circular E) revision date 5/29/09, page 14-15 describes the treatment of federal withholding for supplemental wages (including bonuses.)
It you do not have a copy of Pub 15, it can be found on the IRS.gov website. Just enter pub 15 in the search.
The answer to your question has variables.