I don't want to start an arguement here, but forsythia is not shadbush; they are two different species. Both are indicative of warm weather, and the arrival of herring, shad, stripers, though!
The forsythia has been in bloom here for over a week or two, but the shadbush has yet to surface around here. Shadbush is actually a native tree of the Hudson valley called serviceberry, and has white flowers, and very tasty berries in June, similar to blueberries, but actually better, in my opinion! The birds love them, so they don't last long!