Most probably Witch Hazel, Hamamelis crosses, an ornamental. Or spicebush, Lindera benzoin, wild wetland plant? Possibly corylopsis.

Thanks birdgardner. It's the lindera benzoin - checked your suggestions on google images. We have several kinds of witch hazel so I knew if wasn't that. Since the spicebush attracts swallowtail butterflies I am tempted to obtain a plant or two. I guess it's considered a bush or shrub rather than a small tree but I still think it looks like a tree. Thanks again.

Wow, spicebush is blooming in Princeton already? Mine is a long way from blooming and I've not seen any in bloom here in the North Branch area where I work.

The witchhazel is going strong - it was ever so fragrant over the weekend.

Could it possibly be Cornus mas? I don't have any but I believe it blooms late winter or very early spring.

Here is a link that might be useful:

Hi njtea,
You had me going there for a minute with the photo of the cornelian cherry (cornus mas). But after looking at more photos of it (the fruit gave it away) I remembered that we had a couple of bushes in front of our old townhouse. It's definitely a spicebush. I just bought several bareroot plants because I liked the look of it so much. I haven't seen very many at all around the neighhood or neighboring towns but the Princeton U. campus has several nice specimens in full bloom. Apparently they come in several shades of yellow. Mostly the ones I've seen are a rich gold but there's one bush in Princeton that's a lighter yellow-green which is more to my liking but they are all quite striking and beautiful especially when there's not much else blooming this early. I also noticed that the magnolias on campus were just about ready to bloom and some of the stellas had actually opened a blossom or two.

Our witchhazels are past bloom, I too love the scent but the winterhazel is starting to bloom now with it's long drupe of flowers. Thanks for suggesting the cornus mas