At this time of year you can often see the most birds where you find the most berries. The multi-flora rose is an invasive and non-native plant but the tiny hips that remain at this time of year seem to be a favored food for many birds, including a very possessive and aggressive mockingbird that hangs out in the bush in my backyard.Barberry is another plant that supplies food for many birds at this time of year. There is a native barberry but the most pervasive one is the Japanese barberry, which is non-native and also very invasive. Unfortunately both these non-native plants are easily available at many local nurseries.
One plant that I believe is a native, at least to New England, is the privet. Known by most of us as "the hedge" privet has long been a favorite among those who want quick growing and easy to care for hedges. Many folks never see the masses of sweet smelling white flowers late in mid summer or the subsequent dark blue berries because they constantly trim and reshape their hedges. Hedges grown wild, however, put forth multitudes of these apparently very tasty berries.