The sparrows were all Song Sparrows and Dark-eyed Juncos, with juncos making up about two-thirds of the total. A couple robins also dropped down to feed in the same area. There was a park road nearby with sloped snow embankments. It was amusing to watch some juncos skidding down the embankment as if they were sledding or skiing. They did not seem any worse off for it.
One junco seemed to have some snow and grass stuck to its wing. I assume that it got the snow off eventually as no junco appears that way in subsequent photos.