Sorry, nope not Confederate. I'm not a "Kepi Guru" though they're around somewhere, I would say he a Yankee. Looks to me like a forage cap with a custom regimental insignia and some sort of plume. Odd place for a plume.
I suspect that this is a Lt in the 3rd MA, which was formed largely in Boston, it is certainly an early war photograph. As adeptly mentioned previously, he appears to be wearing an enlisted issue forage cap with applied adornment.