We have over 35 what seem like Elderberry trees,?

in the midst of a maple forest and open field in Ontario. The berries are in clusters of 5 on a one inch tiny branch. The trees range from 6 feet to 30 feet. The berries are red in the fall and are now purple and very tart tasting. The birds eat them in the spring. Im told they arent Eldberries. Does anyone know what they are?