On a cold but sunny day this winter, I noticed a robin staring in my kitchen window as I did the dishes. Ten robins were feasting on shrivelled dark purple berries on the deciduous tree by the fence--a tree that had "planted itself" in my city backyard. Since the tree shades my frozen-over birdbath, I clued-in that the birds might be thirsty and took out some warm water to pour on top of the snow and ice in the birdbath. Many of the birds took a long drink before they went on their way late that afternoon. I enjoyed watching them while I finished my work in the kitchen. The berries have also sustained families of cardinals.
Since the tree (and another further along the fence) sprung up in the garden "spontaneously," I did some research to find out what kind of tree it was. I'm guessing that it's an Alleghany Serviceberry, a native tree that attracts butterflies in the spring and birds in the winter. You can see pictures of it here http://thegreenmanfld.blogspot.com/2009/04/low-management-allegheny-serviceberry.html. I'll post a photo of my own tree when it blooms.
If you're thinking of adding a low-maintenance bush or tree to your garden this year, this is one I'd recommend.
